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Hylomorphism and Diachronic Identity: A Thomistic Approach

A DISSERTATION

Submitted to the Faculty of the

School of Philosophy

Of The Catholic University of America

In Partial Fulfillment of the Requirements

For the Degree

Doctor of Philosophy

Patrick Joseph Rooney

Washington, D.C.

2017

Hylomorphism and Diachronic Identity: A Thomistic Approach

Patrick Joseph Rooney, Ph.D.

Director: Michael Gorman, Ph.D.

Philosophers have struggled to agree on a satisfactory theory of diachronic identity, or identity through time. There are two opposing families of theories, perdurantism and endurantism, each with its shortcomings. Perdurantism, on the one hand, defends many claims that appear to conflict with prephilosophical views of change and substance-feature relations. For instance, most perdurantists argue that change is not a matter of the same object having and then losing a feature; rather, change amounts to the successive existence of various “temporal parts” of the object, some of which have the feature, some of which do not. Endurantism, on the other hand, claims to defend a commonsense view of change and identity. However, endurantists struggle to provide a coherent account of the central notion of their theory, the “whole presence” of a persisting object through change.

This dissertation outlines and defends an endurantist theory that overcomes the shortcomings of previous theories of diachronic identity. This theory, hylomorphic endurantism (HE), builds on the

Aristotelian ontology of Thomas Aquinas. Unlike other theories, it accounts for the identity of individual substances in terms of the identity of two ontological constituents: substantial form and matter. In drawing on Thomistic ontology for principles of identity, HE solves the main problems

of perdurantism and previous versions of endurantism. In contrast to perdurantism, HE defends a view of change in which a single individual directly possesses the features that it gains and loses. HE also articulates exactly how an individual can be wholly present through changes that are numerous and profound.

In addition to showing how HE can address well-known puzzles about diachronic identity, I argue that the theory offers solutions to unexplored but important puzzles about self-change. In this phenomenon, an individual causes a change in itself. The ability of some individuals to change seemingly essential features is paradoxical; it suggests that an individual possesses the ability to make itself an essentially different kind of being. By demonstrating how radical self-change is possible without essential change, HE resolves this paradox.

This dissertation by Patrick Rooney fulfills the dissertation requirement for the doctoral degree in Philosophy approved by Michael Gorman, Ph.D., as Director, and by Gregory Doolan, Ph.D., and Kevin White, Ph.D., as Readers.

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Michael Gorman, Ph.D., Director

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Gregory Doolan, Ph.D., Reader

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Kevin White, Ph.D., Reader

CONTENTS Acknowledgments ...... v Introduction ...... 1 Chapter 1: What a Theory of Diachronic Identity Must Do ...... 8 Scope of the Inquiry ...... 9 Problems about Diachronic Identity ...... 11 Indiscernibility of Identicals ...... 11 The Problem of Temporary Intrinsics ...... 15 The Problem of Material Constitution ...... 18 Self-Change ...... 20 Explanatory Power ...... 34 Conclusion ...... 44 Chapter 2: Current Theories of Diachronic Identity and Their Shortcomings ...... 45 The Fundamental Distinction ...... 45 Perdurantism ...... 50 Endurantism ...... 54 Varieties of Perdurantism ...... 63 Varieties of Endurantism ...... 67 Perdurantism’s Implausible Conclusions ...... 72 Endurantism’s Lack of Explanatory Power ...... 79 Conclusion ...... 87 Chapter 3: Diachronic Identity in Thomas Aquinas ...... 89 A Different Theory ...... 89 The Basics: Substance, Form, and Matter ...... 93 More Thomistic Metaphysics: Esse, Accidents, and Properties ...... 109 Thomas on Identity ...... 114 Thomas as a Proto-Endurantist ...... 114 The Principles of Identity ...... 120 How Form and Matter Are Principles of Identity ...... 126 Rival Interpretations of Thomas ...... 141

iii

Substantial Form as the Sole Principle of Identity...... 141 Esse as the Principle of Identity ...... 148 Conclusion ...... 158 Chapter 4: The Problems of Diachronic Identity Resolved ...... 160 Ontological Explanation in HE ...... 161 Whole Presence Explained ...... 168 Leibniz’s Law Reframed ...... 175 The Problem of Temporary Intrinsics Neutralized ...... 181 The Problem of Material Constitution Solved ...... 189 Taking Stock ...... 209 Chapter 5: Identity through Self-Change—HE on Embryonic Development ...... 211 Thomas’s Theory of Embryological Development ...... 213 Thomas’s View of Development in Relation to Diachronic Identity ...... 226 Objections to the Thomistic View and Similar Viewpoints ...... 238 Developing a Hylomorphic Alternative: A Deeper Understanding of Potentiality ...... 244 Final Remarks ...... 253 Conclusion ...... 255 Bibliography ...... 261

Acknowledgments

I could not have completed this dissertation without the support and patience of my wife, Becca, and the cheerful forbearance of our children, Vivian, James, and Becket. I am also grateful for the guidance of my director, Dr. Michael Gorman; his thoughtful criticism has improved this dissertation in many ways, above all by making it much clearer. Special thanks are due also to my readers, Dr. Gregory Doolan and Dr. Kevin White, for suggesting several improvements to the arguments within.

INTRODUCTION

Identity through time, or diachronic identity, seems uncomplicated when approached casually. In most instances, it is clear when two objects are the same or different, and it is usually easy to tell whether something has remained the same through time. Some cases may seem puzzling (Is the bird in the yard the same as the fledgling from a few weeks ago?), but better evidence typically provides the answer. When matters get truly difficult, the advent of new technology for detecting and tracking microscopic phenomena sets everything aright.

This view of identity assumes that puzzles are always about the evidence that is available to make judgments about identity. On this view, puzzles arise when there is a lack of evidence, and the solution to every puzzle is to acquire better evidence. What this approach to identity ignores is that some difficult cases raise questions about the very nature of identity. Mere observation is not adequate to solve these.

Take two simple examples. Is a monarch butterfly the same as the caterpillar that preceded it? Is a man the same as the zygote from which he developed? Observation suggests the answer, “Yes, in some ways; not in others. Rewrite ‘the same as’ to be ‘the same ______as,’ fill in the blank, and the appropriate expert can tell us.” In other words, the tendency is to turn to scientific evidence. Fill in the blank, however, with a suitably abstract term, such as “kind of thing” or “individual,” and it is no longer clear that scientific evidence can serve as an authority. This line of inquiry asks for a general explanation of what it is to belong to a kind or to be a particular individual, not for the membership

2 criteria of a scientific genus or species. Asking for such an account of general, basic concepts is a philosophical question, not an inquiry for natural science.

These pre-philosophical challenges represent the embryo of one of the problems considered in this dissertation, namely self-change, or an organism’s self-guided transformation from possessing one set of characteristics to possessing a very different set of characteristics. I will say more about this shortly. Although self-change is fascinating in its own right, the primary impetus for this work is the existence of many puzzles in the philosophical literature that remain subjects of ongoing debate. The

Indiscernibility of Identicals, for instance, is a widely (but not universally) held claim about identity: identical things must share all the same features. This principle seems sensible enough at first glance—being identical means being the same through and through—but it proves difficult to endorse for diachronic identity, or identity over time. Things change over time—they lose and gain features—but they can be said to change only because they are the same entities, not a series of different entities appearing successively in the same place. Recognition of this fact, coupled with a commitment to the Indiscernibility of Identicals, leads many philosophers to devise various theories of how the two claims are compatible. Kindred puzzles, more or less removed from everyday concerns, abound in philosophical writing.

This work argues that puzzles about identity prove intractable without a great deal of carefully worked out ontology. The problems about developmental changes in caterpillars, humans, and the like demand an account of those changing things and the peculiar processes they undergo that we call development. The problems of contemporary philosophical literature may appear to demand

3 less because they deal with more abstract questions, such as “How does an object remain the same if it changes with respect to just one feature?” Yet even this modest inquiry asks for an account of what it is to be some particular object and how a single change may affect the identity of that object.

Beyond pointing out a need for an ontology that can guide an investigation into identity, this work draws attention to such a theory. More precisely, I argue that almost all the resources required for the theory appear in the work of Thomas Aquinas. Thanks in large part to its Aristotelian foundations, his thought contains just the ingredients for a theory of identity: a metaphysics that distinguishes essential and inessential constituents, a natural philosophy that addresses change, and—incidentally—a theology that investigates many problems about identity that are also relevant to philosophy. Importantly, there are many good arguments for Thomas’s positions apart from their usefulness in understanding identity. This distinguishes Thomas’s thought from the many views of diachronic identity that are formulated without concern for other philosophical issues.

Because there are several lines of inquiry in this work, some explanation of how they fit together may be helpful. The first two chapters set forth the central problem of this work. Chapter 1 outlines the challenges for a theory of diachronic identity. These are of three kinds. First, there are well- known puzzles about diachronic identity: explaining identity through change in the face of Leibniz’s

Law (the principle of the Indiscernibility of Identicals mentioned above); the problem of temporary intrinsics, which purports to show that no individual can possess incompatible intrinsic features; and the Problem of Material Constitution, a host of puzzles that require the solver to give up at least one plausible thesis about change. In this chapter I also introduce second challenge, a problem that is

4 not treated systematically in the literature but nonetheless merits a closer look, the problem of self- change. The crux of the problem is that some organisms appear to change with respect to certain defining features and yet also appear to be responsible for causing these changes. The change itself is allegedly a basis for denying that the individual remains numerically the same, yet the individual’s causal role in the change suggests that the same subject persists through the change. A satisfactory theory of identity must address these puzzles. It also should address a third challenge: furnishing a criterion of identity, or a reason in virtue of which one may say that a thing is the same. To conclude chapter 1, I explain why arguments against the possibility of such a criterion are misguided.

Chapter 2 critiques the two families of theories that claim to solve the puzzles of diachronic identity.

The first group, perdurantist or four-dimensionalist theories, argue that objects that persist through time are composed of a series of “temporal parts.” One could conceive of these parts as temporal cross-sections of the object’s life or “career”—whatever one chooses to call the entirety of its existence through time. Importantly, properties and spatial parts belong directly to the temporal parts and only indirectly to the wholes composed of these parts. Proponents of endurantism claim that this ontology dissolves many puzzles about diachronic identity that arise when one holds that objects themselves possess properties and spatial parts.

The chief rival to perdurantism is endurantism (or “three-dimensionalism”), which holds that objects themselves possess spatial parts and properties directly. On this view, temporal parts are unnecessary. As a way of distinguishing their view from perdurantism, endurantists often say that objects are “wholly present” at any instant of their existence, but they seldom draw out the

5 ontological implications of this claim. This important but murky notion of whole presence receives further attention in chapter 4.

Contemporary perdurantist and endurantist theories have deep problems, as I show in the final sections of chapter 2. I argue that perdurantism cannot offer satisfactory accounts of phenomena such as growth, where the subject is clearly a persisting object rather than a temporal part.

Endurantism may be able to address this issue, but current versions of endurantism suffer from a variety of defects, most related to a lack of ontological commitments.

Given the weaknesses of current theories of diachronic identity, we need to find a better endurantist theory or create one. Chapter 3 sets out to find such a theory in the work of Thomas Aquinas.

Thomas himself of course was not a professed endurantist; he lived 700 years too early. His writings, however, indicate an affinity for “proto-endurantist” positions, including a distinction between successive existence (akin to being an entity with temporal parts) and non-successive existence (akin to being an entity with no temporal parts). Furthermore, his work offers an ontological foundation for a theory of identity, namely an Aristotelian or hylomorphic ontology. Not only does Thomas’s thought include the conceptual apparatus to solve puzzles about identity, but it also boasts independent justification: he argues for his most important ontological claims on grounds other than their usefulness in solving problems about identity.

The exposition of Thomas’s thought and investigation into the puzzles of identity converge in

6 chapter 4. There I show that the theory of identity latent in Thomas’s writings, which I call hylomorphic endurantism (HE), can address the most common problems about identity over time.

In the course of this argument, it becomes clear that Thomas’s philosophy offers something far more important than solutions to puzzle cases: it articulates a principled understanding of identity that enables the Thomist to address perdurantism’s basic conceptual mistakes about identity. Chief among these errors is a “strict” notion of identity—the view that numerical identity amounts to sameness with respect to every feature and part. By demonstrating why this conception of identity is mistaken, hylomorphic endurantism removes much of the existing confusion from the debates about identity through time.

The last chapter turns from commonly discussed puzzles to an overlooked problem: self-change, specifically the radical ways in which organisms change themselves during development. The question of whether organisms remain numerically the same through development receives little attention in the philosophical literature. Similarly, although some philosophers note that these changes are initiated and directed by the organism itself, the implications of this point have not been studied. To be sure, within the realm of bioethics, there are debates about the point at which procreation generates a new life and when that life merits the label “person.” Nonetheless, a close study of how a broader theory of identity should treat the problems raised by developmental change does not exist. This chapter fills this void by critiquing Thomas’s treatment of identity through embryonic development. Interestingly, his writings contain extensive remarks on identity through human embryogenesis. These remarks are often mistaken in large part because Thomas lacks the understanding of embryology needed to comment insightfully on identity through development.

Nonetheless, it is possible to draw upon Thomistic principles so as to outline a coherent view of identity through the process of development.

In sum, the goal of this work is to show that hylomorphic endurantism contains all the elements of a successful theory of diachronic identity. HE solves puzzles from the philosophical literature, addresses difficult questions about self-change, and avoids the pitfalls of other endurantist theories and perdurantism. All HE’s positions flow from Thomist-Aristotelian principles, which offer the benefit of resolving many philosophical issues aside from the questions about identity that are central to this dissertation. There are therefore many reasons to entertain the possibility that we should embrace HE as a theory of diachronic identity.

CHAPTER 1: WHAT A THEORY OF DIACHRONIC IDENTITY MUST DO

Puzzles about identity over time surround us. Consider, for example, the relationship between an acorn and an oak. The acorn looks nothing like the oak. The acorn is minute, compact, and smooth.

The oak is sprawling, leafy, and rough. The acorn also acts nothing like an oak. The acorn ripens gradually while awaiting the right conditions to sprout. The mature oak synthesizes new food, sheds its leaves (if a member of a deciduous species), and reproduces by dispersing acorns.

The differences between the acorn and the oak are so striking that it is plausible to deny that an acorn is an oak tree. But what precisely does this denial mean? It cannot be that there is no continuity between an object that is an acorn and an object that is an oak, for one grows into the other. Perhaps then it means that no object that is an acorn is also an oak. This formulation certainly is correct so long as the analysis focuses on one instant in time: nothing is an acorn and an oak tree simultaneously. But does the denial mean something more? Specifically, is it reasonable to deny that there is any one object that is an acorn at some time and an oak at another time?

This last question touches upon diachronic identity, the identity of an object through time and usually through change as well. What change an object can endure has been a matter of speculation from antiquity to the present. For all the attention it has received, however, diachronic identity remains a subject riddled with unsettled problems. It is the aim of this dissertation to propose several novel and robust solutions to these problems.

Scope of the Inquiry The following chapters will deal with a specific type of diachronic identity: numerical identity, or the identity of an individual. This type of identity is intuitively simple to explain: it is the “sameness” of a single being through time and through change—assuming that something can in fact remain the same through change. This sameness includes and extends beyond being the same type of thing, or identity of kind or species. Thus, remaining an antelope for a day is an example of diachronic identity of kind; being this antelope for a day is an example of diachronic numerical identity.

Some questions can arise as to what types of entities can be numerically identical. Can properties, such as shades of blue? How about actions, such as mowing the lawn and doing a good deed? Are abstract objects able to be numerically identical? Prescinding from such questions, this work will examine the numerical identity of concrete, natural objects exclusively. It will not discuss the numerical identity of properties, relations, or any other sort of entity except when needed to address questions about the numerical identity of objects. Moreover, the work is not concerned with abstract objects or immaterial entities. For reasons explained in Chapter 3, I endorse an Aristotelian substratum theory and therefore consider material objects to consist of a foundational substrate and properties rather than bundles of tropes or universals.1 Individual organisms stand out as the paradigmatic and non-negotiable examples of natural material objects,2 but other possible members of this category include minerals, molecules, and freestanding atomic and subatomic particles.

Nothing important within this work rests on the precise membership of this list.

1 More precisely, I hold a Thomist view that matter and form jointly compose the substrate, which “supports” necessary and non-necessary properties (‘properties’ and ‘accidents’ in the terminology of medieval metaphysics). 2 By “individual organisms” I intend to exclude such creatures as siphonophores, which are difficult cases and certainly not paradigmatic.

Despite this restricted scope, I intend to address several fundamental questions about diachronic identity. Most importantly, I will explain what the diachronic identity of natural, material objects consists in. I also will address several recurring puzzles about diachronic identity, and I will treat some difficulties about diachronic identity that have gone unnoticed in the literature. Hopefully, providing these explanations for a restricted (but numerous) set of beings will yield some conclusions relevant to inquiries into the diachronic identity of other kinds of entities.

At the heart of this work is the rivalry between two contemporary theories of diachronic identity: perdurantism and endurantism. Although I shall discuss both at length in later chapters, preliminary formulations of the two theories will facilitate the present discussion of requirements of a theory of diachronic identity. Thus, perdurantism claims that an object can remain numerically the same through changes only by being composed of distinct temporal parts, or parts that occupy a specified length of time in the way that spatial parts occupy a defined spatial region. Perdurantists argue that an object cannot have a property F at time t and lack that property at time t' except by having one temporal part that is F and a distinct temporal part that is non-F. Accordingly, objects that persist through time do so by existing “one part at a time” on the perdurantist view. In contrast, endurantism holds that a persisting object can remain numerically the same without the mediating role of temporal parts. On the endurantist view, objects have no temporal parts; they possess their properties directly, without the mediation of temporal parts. Therefore, endurantists say that a persisting object is “wholly present” at every moment of its existence.

Problems about Diachronic Identity The primary impetus to construct and amend theories of diachronic identity comes from a host of general problems and puzzle cases. While these have received significant attention in the philosophical literature, they are by no means settled. To emerge as a viable theory of a diachronic identity, a system must advance the discussion of these problems beyond the status quo. This work will focus on the three most prominent puzzles, namely the Indiscernibility of Identicals, the problem of temporary intrinsics, and the Problem of Material Constitution.

In addition to these well-known problem cases, there are some difficult questions about diachronic identity that have gone unasked. In particular, processes of self-change, such as biological development, involve radical changes in the structure and function of natural substances. Yet these changes usually are part of a predictable, regular process that is directed at least in part by the substance itself. A robust theory of diachronic identity must be able to reconcile the conflicting intuitions that arise in such cases.

Indiscernibility of Identicals At a bare minimum a viable theory of identity must confront the widely (but not universally) accepted principle of the Indiscernibility of Identicals (PII). In its most general form, the principle states that any two objects x and y are numerically the same only if they share all the same properties. In second order logic, the principle is formulated as follows:

x=y → ∀F(Fx ↔ Fy)

The principle is included as one of the conjuncts of Leibniz’s Law (the other conjunct is the Identity of Indiscernibles), and most philosophers attribute it to Leibniz. His writings supposedly present the principle for the first time.3 However, one can find discussions of very similar principles in the work of earlier philosophers. Thomas Aquinas, for example, considers and rejects the claim that numerical identity requires the sameness of both necessary and accidental (non-essential) properties across time.4

The Indiscernibility of Identicals raises no difficulties in many situations. For example, synchronic cases, which deal with identity at a single instant, are generally unobjectionable. If Jeff Sessions is the

Attorney General, then Mr. Sessions and the Attorney General cannot differ with respect to any property at any given instant.

In contrast, if one claims that the Indiscernibility of Identicals is a condition of diachronic identity, a problem arises immediately. According to the diachronic version of the principle, any object O that is F at time t and not-F at time t' is not numerically identical across these times. In other words, a diachronic version of PII precludes numerical identity through change.

Many philosophers seem to embrace a diachronic version of the principle. For example, Mark Heller uses the diachronic version of PII to motivate his arguments in favor of perdurantism. He contends that his present bearded self cannot be the same as his beardless seven-year-old self because the two

3 A list of texts in which Leibniz discusses the Identity of Indiscernibles and related principles appears in Ari Maunu, “Indiscernibility of Identicals and Substitutivity in Leibniz,” History of Philosophy Quarterly 19.4 (2002), p. 379n10. 4 Quodlibet 11, q. 6, ad 1.

13 do not share the property of being bearded.5 In virtue of differing with respect to one property (at least), the seven-year-old Heller and the adult Heller are non-identical. Similarly, Trenton Merricks views the diachronic version of the principle as a prima facie obstacle to his own endurantist theory.

Assuming that “identity entails indiscernibility,” Merricks notes that an object O that has property F at t but lacks F at t' does not appear to be indiscernible at those two times. If this is the case, he concludes, then endurantism fails as a theory of identity.6 Consequently, properly interpreting and applying the principle is a central part of expounding a theory of diachronic identity.

Notably, the motivation for the diachronic version of PII is obscure. No philosopher appears to state why the principle should apply diachronically. Support for this application may arise from the belief—which I share—that synchronic identity and diachronic identity are not two relations or phenomena but one, identity simpliciter. As Ted Sider writes, “‘Identity over time’ is nothing but identity itself.”7 Accepting this view, one might return to the formulation presented above and conclude that the objects x and y must share all their properties even if ‘x’ refers to an object at one instant of time and ‘y’ at another instant. Sider endorses just this conclusion: “The demands of the notion of identity are high: identical things must share all their properties.”8

Now, although the synchronic version of the principle is intuitively plausible, the diachronic counterpart is not so obvious. That is, there are pre-philosophical reasons in favor of an indiscernibility requirement for synchronic identity, but no such pre-philosophical reasons for

5 Mark Heller, “Things Change,” Philosophy and Phenomenological Research 52 (1992), pp. 696-97. 6 Trenton Merricks, “Endurance and Indiscernibility,” The Journal of Philosophy 91 (1994), p. 166. 7 Theodore Sider, Four Dimensionalism (Oxford: Oxford University Press, 2001), p. 149. 8 Four Dimensionalism, p. 167.

14 endorsing a similar requirement for diachronic identity. It seems obvious that if the man in the corner is the President of the United States, then the man in the corner and the President must agree in every property. However, it is not so evident that a tiger cub and an adult tiger, if identical, must share all the same properties. In fact, at first glance, there seems to be no such requirement for diachronic identity. How then does one motivate the diachronic version of the principle?

The adoption of a diachronic version of PII seems to rest on an implicit philosophical semantics—a tenseless semantics, in fact. Namely, a diachronic version of PII seems to entail that from the sentences

(1) O is F at t

and

(2) O is not-F at t'

We can infer the following two sentences:

(3) O is F and

(4) O is not-F.

In other words, an assumed tenseless semantics leads to the contradiction that O is F and O is not-

F. Merricks points to this assumption when he discusses one proposed solution to the problem, which he calls “taking tense seriously.” According to this solution, which Merricks adopts in a revised form, the time indices in propositions such as ‘O is F at t’ and ‘O is F at t'” represent ontic differences. Accordingly, it is wrong to generalize both propositions to the form “O is F”, which elides these distinctions. Furthermore, these ontic differences are the very reason why statements

15 such as ‘O was F’ and ‘O is not F’ are not contradictory; one is not making incompatible claims about the state of the world. The “serious-tenser” takes this (unarticulated) ontic difference as a point of departure and tries to develop a semantics consistent with the assumption.9

Unfortunately, developing a revised endurantist semantics will not address the problem fully. If

Merricks and those who take tense seriously are correct, then the diachronic version of the principle is simply false—not merely semantically, but ontologically as well. Simply put, diachronic identity does not demand indiscernibility. This much may be a fundamental, axiomatic truth, but the opponent of the diachronic version of the principle still has a question to address: if identity over time does not consist in indiscernibility, what does it consist in? This question is the primary challenge arising from reflection on the principle.

The Problem of Temporary Intrinsics David Lewis posed the problem of temporary intrinsics in On the Plurality of Worlds as “the principal and decisive objection against endurance.”10 The problem is perhaps the most frequently discussed difficulty in the literature that is framed generally and not in conjunction with any sort of “puzzle case.”

As stated by Lewis, the problem of temporary intrinsics holds that an object O cannot have complementary non-essential intrinsic properties at different times. He writes, “[W]hen I sit, I have a bent shape; when I stand, I have a straightened shape. Both shapes are temporary intrinsic

9 Merricks, “Endurance and Indiscernibility,” p. 170. 10 David Lewis, On the Plurality of Worlds (Oxford: Blackwell, 1986), p. 203.

16 properties; I have them only some of the time. How is such change possible?”11 In other words,

Lewis is making a claim about objects of a kind K that can exist with or without an intrinsic or non- relational property F. For instance, being freckled is a non-essential intrinsic property of some humans. On Lewis’s view, a human cannot gain or lose freckles while remaining identical, for then the same thing would possess complementary properties. It would be true that she is freckled and true that she is not freckled.

The problem bears a strong resemblance to the Indiscernibility of Identicals. Both the problem and the diachronic version of indiscernibility deny that an object O can be F at one time and not-F at another. However, Lewis’s development of the problem of temporary intrinsics adds some further metaphysical trappings. Lewis wonders how O can acquire and lose intrinsic properties so long as O is “wholly present” at any given time. Lewis’s understanding of “whole presence”—usually an endurantist term of art—in this context rests upon a parallel with his theory of modal realism. On this theory, the same individual cannot exist in two distinct possible worlds, for then the same individual could possess complementary properties timelessly—one complement in one possible world, the other complement in a second possible world. Because Lewis takes all possible worlds to be realized, possessing complementary properties in multiple worlds amounts to a truly contradictory state of affairs. By way of parallelism, an individual cannot possess complementary intrinsic properties at different times because the individual would possess incompatible properties timelessly. As David Oderberg notes, those who reject Lewis’s modal realism, or at least those who reject the parallel between time and modality, will find the problem facile; the law of non-

11 On the Plurality of Worlds, p. 204.

17 contradiction does not exclude the possession of complementary properties at different times.12 Yet many philosophers have been swayed by Lewis’s analogy and try to address the problem within his framework.

Lewis suggests that there are three solutions to the problem, only one of which satisfies him. First, one may deny that putatively intrinsic properties, such as shape, are truly intrinsic. Instead, one may claim that these properties are in fact relations that an object bears to a time. On this view, an object changes by bearing different relations to differing times. Lewis finds it incredible to conceive of properties such as shape as relations, so he summarily dismisses this option.

As an alternative, Lewis considers that an object may have only those properties which are true of it at present. Ascriptions of past or future properties are “like false stories,” devoid of any relation to reality. This theory, known as ersatzism, holds that only statements about the present and timeless statements can be true. This solution is inadmissible on Lewis’s view, since it is obvious that there are truths about the past and (perhaps) the future.

Finally, Lewis proposes a version of perdurantism: differing temporary intrinsic properties belong to different things, namely different temporal parts. Thus, these intrinsic properties do not belong directly to the whole object, O, though O may possess other properties directly. Accordingly, a change in temporary intrinsic properties entails a change in temporal parts but not a change in the

12 David Oderberg, “Temporal Parts and the Possibility of Change,” Philosophy and Phenomenological Research 69:3 (November 2004), p. 693.

18 identity of the object. The indirect possession of properties through temporal parts allows O to remain numerically identical as its properties change.

Proponents of endurantism have argued about the best means of addressing this problem. Jeffrey

Brower, for example, recommends adopting two elements of an Aristotelian metaphysic: a substratum theory and a theory of “accidental sameness.” 13 Merricks, in contrast, adopts the strategy of ‘taking tense seriously’ discussed above. Michael Rea offers yet a third endurantist solution: embracing adverbialism, the view that all property possession is qualified, so that O is never F simpliciter but rather t-ly F, where t is a time index.14 Clearly, addressing the problem of temporary intrinsics remains a point of contention among endurantists.

A difficulty remains even for endurantists who agree with Oderberg—as I do—that the problem is in fact a pseudo-problem, predicated upon the acceptance of a misguided theory of modality. One still must explain what it means for an object to be “wholly present” at different times when that object’s parts and properties may not be the same at those times. In other words, the problem of temporary intrinsics is a call for a more robust definition of whole presence.

The Problem of Material Constitution In fact a collection of several ancient and contemporary puzzles, the Problem of Material

Constitution (PMC) received its name from Michael Rea. According to Rea, four puzzles, including the classic Ship of Theseus paradox and the contemporary paradox of Lumpl and Goliath, share a

13 Jeffrey Brower, “Aristotelian Endurantism: A New Solution to the Problem of Temporary Intrinsics,” Mind 119 (2010), p. 898. 14 Michael Rea, “Temporal Parts Unmotivated,” The Philosophical Review 107:2 (1998), p. 246.

19 similar form. If one takes “the ps” to be a plural variable referring to a collective of many individuals—but not the set of these individuals—one can state the problem as follows.15 First, begin with two axioms about identity and composition. One axiom is this: if the ps compose an object a and they compose b as well, then a is identical to b. The second axiom is that any two identical objects are always necessarily identical. In addition to these axioms, one must accept the claim that there is some object of type F that is composed by the ps. Further, one must hold that if the ps compose an F, they compose an object that must bear the relation R to its parts. However, an equally powerful intuition holds that if the ps compose an F, they compose an object that need not bear R to its parts.16 Accordingly, these five assumptions lead to incompatible conclusions when determining whether the object that bears R to its parts remains the same when it no longer bears R to those same parts.

One of the PMC puzzles, the growing paradox, illustrates these points nicely. In essence, the paradox holds that a man cannot grow without altering his identity. This is because the particles that compose his body also compose an aggregate; thus, according to the axioms, the body and the aggregate are identical. Now, something of the type aggregate exists only so long as it is composed of exactly the same particles, so the addition of particles by growth amounts to the generation of a new aggregate. Therefore, since the body and the aggregate are necessarily identical, the addition of particles yields a new man. Yet this conclusion conflicts with the belief that bodies remain numerically the same through changes of particles. Consequently, one must deny at least one of the five plausible assumptions to escape the problem.

15 As an example, the phrase “all the fish in the sea” refers to the collective of all fish in the sea, not the logical object that is the set of all fish in the sea. 16 Michael Rea, “The Problem of Material Constitution,” Philosophical Review 104 (1995), p. 527.

The PMC is relevant to diachronic identity because its constituent puzzles derive their paradoxical nature from changes that call into question the identity of the object changed. The puzzles arise whenever objects of type F change so that they no longer bear a seemingly essential relation R to their parts. The loss of this relation leaves one wondering whether any F endures at all. A robust theory of diachronic identity must provide some basis for determining what sorts of relations, if any, are truly essential for diachronic identity.

Self-Change The three foregoing problems enjoy an established place in the philosophical literature. Notably, they consider diachronic identity at a level of great generality, accounting for any sort of change in almost any type of object. Yet more specific sorts of changes in restricted categories of objects may raise additional problems. Unfortunately, the literature on diachronic identity largely has failed to examine these limited categories of change. This is no small failing, for narrow problems that remain intractable to more general approaches may indicate that a general framework must be refined or overhauled.

One overlooked area in the literature on identity is self-change, a phenomenon most evident among organisms. In cases of self-change, an object through its own (possibly aided) activity alters one of its parts or properties. The process of alteration, if sustained and far-reaching in its results, may raise the concern that the original self-changing object no longer exists. This impermanence may reflect either a putative change in essential features or an apparent destruction of the substratum for the

21 change. In both instances, it seems that self-change may be so radical as to eradicate the original self- changing object.

Because the problems arising from self-change have been overlooked, they deserve closer examination. However, given that the very existence of self-change may seem doubtful, some preparatory discussion of the concept is in order.

The notion of self-change is of ancient origin—Aristotle discusses it at length in Physics VIII— and it admits of many variations. In order to explain and defend my conception of self-change, I shall juxtapose my theory with two of the more notable developments of Aristotle’s views, those of Duns

Scotus and Thomas Aquinas.

Examining one conception of self-change, the view developed by John Duns Scotus, shows why self-change initially may sound metaphysically or physically impossible.17 Scotus defends strong self- change, a possibly spontaneous type of change that may occur within an undivided entity, such as an indivisible spherical particle. Someone who endorses strong self-change agrees with three claims:

1) Self-change may be entirely spontaneous, that is, not initiated or aided by an external agent;

2) The change may occur within a homogeneous entity, an entity whose parts are all of the

same type; and

17 My discussion of Scotus is heavily indebted to Peter King’s article, “Duns Scotus on the Reality of Self-Change,” in Self-Motion from Aristotle to Newton, ed. Mary Louise Gill and James G. Lennox (Princeton, NJ: Princeton University Press, 1994), pp. 227-290. The most thorough exposition of Scotus’s views appears in Quaestiones super Libros Metaphysicorum Aristotelis 9, q. 14.

3) The change may occur within an indivisible entity, or a being without proper parts.

Scotus regards strong self-change as a characteristic feature of free will and a common occurrence in nature. There are, however, serious objections to his view. First, strong self-change would seem to allow for violations of various physical conservation principles. For example, the spontaneous initiation of physical movement would violate the first law of thermodynamics, the principle of conservation of energy. Because an object that causes its own physical activity with no external input must create a new source of energy, energy is not conserved.18

As King notes, strong self-change could be criticized for being explanatorily vacuous. Traditionally, self-change encompassed both the initiation of processes and the cessation of these same processes.

Walking and halting would be typical examples. That is, a being that can start walking can also stop itself. On a theory of strong-self-change, the same, indivisible individual is solely responsible for both the walking and the halting. But then it is difficult to say why the individual walks rather than halts beyond the fact that it simply does so. The defender of strong self-change cannot appeal to external conditions or to the involvement of different internal physical parts to account for different sorts of self-change.19

18 This is not to deny that energy can be stored; rather, the point is that the initiation of movement at a given time requires some external impulse, whether immediately prior to that time or at some earlier point. 19 “Duns Scotus on the Reality of Self-Change,” p. 237. Strictly speaking, the proponent of strong self-change might avail himself of this line of defense in some circumstances. However, his support of strong self-change entails that he does not recur to external influences or internal differentiation in all circumstances.

To refute the charge of explanatory vacuity, a proponent of strong self-change must posit some metaphysical differentiation within the self-changer. According to Scotus, distinct metaphysical constituents—but not distinct physical parts—are responsible for opposing actions such as walking and halting. More specifically, he holds that there are distinct active potencies corresponding to incompatible actions. Which potency is activated is determined by the individual’s cognitive power, so the proximate cause of any self-change lies within the individual. Cognition, however, is actuated in turn by external causes, as Scotus admits. Thus, at least in the case of beings that can act in contrary ways, strong self-change does indeed depend upon external causes.

This qualification of self-change as sometimes externally caused, coupled with a lack of scientific plausibility, demonstrates that strong self-change stands in need of modifications. For the instances of self-change in which Scotus allows an external cause, namely cases of animal motion, are the most obvious examples of self-change. His other putative instances of self-change, such as the downward motion of heavy objects, are now ascribed in part to external causes in light of contemporary scientific theory.

The shortcomings of strong self-change suggest that we should reject the central claims of the theory, or, at the very least that we should refrain from affirming them unless confronted with better evidence and arguments.

Fortunately, there is no need to equate self-change with strong self-change. Instead, one may acknowledge only weak self-change, which always takes place between parts in a substantial whole.

One part of the whole, the “active” part, is responsible for φ-ing, while another part, the “passive”

24 part, is φ-ed. Weak self-change also differs from strong self-change in relying upon external causation in all cases. The initiation of any weak self-change C must follow upon some external event E. Thus, there is no spontaneous causation.

Despite lacking the exotic properties of strong self-change, weak self-change shares several properties with strong self-change that differentiate both categories from merely externally effected changes. Once again, the fullest exposition of these features appears in the work of Duns Scotus.

This time, however, the features pose none of the prima facie problems associated with strong self- change and yet still clearly demarcate self-change from other types of change.

The first important feature of self-change is that it occurs in an individual that has an ability to produce and experience the same sort of change. More formally, a self-changing object O has the ability to φ and the capacity to be φ-ed. Returning to Aristotelian terminology, the self-changer has an active potency to φ and a passive potency to be φ-ed. As an example, the contraction of a muscle involves the “twisting” of an acetylcholine receptor when it binds with the neurotransmitter acetylcholine; the acetylcholine has an active potency to twist the receptor, and the receptor has a passive potency to be twisted.20 In a similar manner, certain muscle cells of octopuses and squids possess the active potency to squeeze and distort small sacs of pigment, which have the passive potency to be bent and flexed; this is the mechanism for camouflage in these animals. To qualify as a self-change, it is necessary that the change in an object be, at least in part, a result of its exercise of its active potency on one of its passive potencies.

20 Because the conformational change or “twisting” is a complex interaction, this description is a simplification. A more thorough description would discuss the active and passive potencies of parts of the acetylcholine and parts of the receptor.

A second important point about self–change is that most self-changes (and all those that interest us) involve equivocal causation, or the production of a property F by an agent that is non-F.21 The conversion of one form of energy into another is a common instance of equivocal causation.

Chemical energy, such as that stored in a bomb, may produce kinetic energy in a storm of flying debris. Notably, the chemical energy does not yield kinetic energy in light of its own kinetic energy.

Similarly, self-change involves a part that is not-F causing another part to be F.

The two features just described distinguish self-change from changes that are merely externally effected. While changes due solely to external effects consist only in the activation of passive potencies, self-change consists first in the activation of an intrinsic active potency and then in the consequent activation of the passive potency by the active potency. In contrast, non-self-changers change only in virtue of their passive potencies. A rock is heated but does not heat itself; water is moved but does not move itself; crystals “grow” but do not generate their own parts. Moreover, although a merely externally effected change may produce a cascade of effects in an object, which may resemble self-changes, the cascade will be effects all of the same kind. For instance, a kitchen

21 All strong self-changes are instances of equivocal causation. To assume otherwise would be to posit that an object that is non-F causes itself to become F in virtue of its F-ness; this is clearly contradictory. Weak self-change, however, may involve univocal or equivocal causation. To say that a self-change is univocal is to say that the “active” part of a substance, in virtue of being F, causes the “passive” part to become F. Note also that the external cause that initiates a weak self-change may be either equivocal or univocal. In the first case, a weak self-change is not itself equivocal, but it depends upon an equivocal cause. In the second case, it is possible to show that self-causation is an “accidental” feature of the causal relation as follows. The initial, external cause X acts by form F to cause the active part A to become F. Now it must follow that A in turn immediately causes the passive part B to become F, for if there is some other cause necessary to make B become F, then that additional cause must act in virtue of being non-F, and the causation is equivocal. Therefore, A is not necessary for causing B to become F; the external cause X could have done so on its own but for some accidental reason (perhaps A lies in greater proximity to B). Consequently, the effects of such univocal cases of self-change could result from merely external causes. In contrast, equivocal cases of self-change require an internal cause. For this reason, only weak self-changes that are equivocal or that result from equivocal causes are of interest for our purposes.

26 sponge moistened on one side may transfer the moisture throughout its parts, but that is not a self- change. Rather, the transfer is a passive diffusion of water from one section of the sponge to another; each section of the sponge has a capacity to absorb water in adjacent sections. Only if some part of the sponge in virtue of its wetness caused an effect other than wetness in a second part would there be self-change.22

An example may help to illustrate these features of self-change more clearly. Within the brain certain neurons release the neurotransmitter dopamine when stimulated. Some of this dopamine in turn binds to the helical loops of receptors attached to other neurons and “unlocks” the receptors to set off a cascade of events within the neuron. Supposing for simplicity’s sake that the release of dopamine is externally triggered, the action of the dopamine on the receptor is an instance of self- change. The dopamine has an ability, an active potency, to twist the receptor, and the receptor has a passive potency be twisted. Thus, there is the internal match of active and passive potencies needed for self-change. Furthermore, the property by which the dopamine effects this twisting is distinct from the property possessed by the altered receptor; the dopamine is at no point configured like the altered receptor. Accordingly, this is a case of equivocal causation.

The basic framework for self-change is now in place. But one could still wonder whether there is really a need for self-change. One could suppose that all changes within substances are purely externally effected. However, this supposition is impossible to sustain. If all changes were externally effected, no substance would ever act upon itself by means of its own abilities or potencies. But it is

22 Here an “effect other than wetness” excludes effects that supervene on wetness, such as becoming heavier or more pliable.

27 clear that some substances do act upon themselves: warm-blooded animals regulate their bodily temperature, plants synthesize their own food, and some organisms fly under their own power.

Furthermore, if there were no self-change, all changes within a substance would simply propagate the same sorts of change caused by extrinsic agents. For example, a substance heated from without might spread the heat throughout its body, but the heating would not result in an entirely new form of internal activity, such as the release of a hormone that regulates blood pressure. But we see that such changes do occur. In short, self-change is a basic datum of biology. There is good reason, therefore, to provide an explanatory framework for self-change.

Someone might argue against this view that only the first, external cause is responsible for the series of effects in the substance. However, this objection rests on a false presupposition. Specifically, the objector must hold that the external cause by itself (or in concert with other external causes) determines the nature of the final effect. This is to say that internal components of the affected subject play no role in determining the effect; there is no transformation of the effect of the external cause E1 into an effect of a different kind E2. Now this sort of transformation is precisely what happens in self-change. The causation involved is equivocal: an internal component that is non-F makes another internal component F. Therefore, the causal powers of first internal component are indispensable in determining the outcome of the causal process, and the external cause cannot be considered the sole cause.

So far I have spoken of self-changes as though they were all momentary and self-contained events.

While many self-changes fit this description, others do not. Numerous momentary self-changes occur within organisms as part of broader life processes such as maturation, gestation, and immune

28 responses. Under the influence of external events, these overarching processes orchestrate numerous self-changes that progress toward some end state: adulthood, birth, health, and so on. It is fitting to call these larger processes self-changes, for they exhibit features parallel to the defining features of momentary self-changes. First, the instigator of the change, often a physiological system or network, such as the endocrine system, possesses an active potency to φ. 23 The instigator’s passive counterpart, often another system or network, possesses a passive potency to be φ-ed. For instance, the human growth hormone released by the pituitary gland has an active potency to stimulate growth through cell division, while cells throughout the body have a corresponding passive potency to undergo division. Second, these processes encompass numerous instances of equivocal causation. For instance, the release of hormones during puberty causes adolescents’ limbs to grow and their voices to drop. Neither the organs releasing the hormones nor the hormones themselves are long-limbed or deep-voiced, but they produce these qualities in the individual.

It is with such large-scale self-changes that philosophical difficulties arise. In particular, the radical changes effected by development pose metaphysical problems. Among the most nettlesome difficulties is the seeming acquisition of essential or defining traits: a mature organism with an essential feature F develops from a juvenile bereft of that feature. The discontinuity in humans is the example most ready to hand: a mature thinker develops from a non-thinking zygote—a creature without even a rudimentary nervous system. But in other organisms the chasm is wide as well: the oak, the adult fish, and the mature beetle have little in common with acorns, roe, and grubs. Each mature organism enjoys a set of essential biological functions that is not found in the juvenile.

23 In many cases, however, the systems involved in these processes are so numerous and interdependent that it makes sense to say that only the organism as a whole possesses the active and passive potencies.

Accordingly, it seems as though the adult differs in kind from the juvenile and hence in number as well.

This difficulty runs deeper than the Indiscernibility of Identicals or the Problem of Temporary

Intrinsics. It points to an apparent rupture in the very kind of life an organism leads— the acquisition of a property that seems to be essential rather than accidental. The difference in kind indicates that the putative temporal parts are not parts of one whole. Thus, the fissure does not appear to be readily bridged by the doctrine of temporal parts.

Peter van Inwagen identifies just this problem of discontinuity in the case of human development. If it is true that zygotes develop into adult humans, he remarks, then it is likewise true that adult humans once were zygotes. Yet this development seems implausible to van Inwagen in light of the necessary properties of zygotes. Because a zygote is a unicellular organism—it is a cell, as van

Inwagen puts it—it cannot be identical to any multicellular organism, including an adult human. The division of a zygote into two cells is either the end of the zygote’s life or the creation of a replica alongside the persisting zygote. Regardless of the option one selects (van Inwagen favors the first), the obstacle to identifying the zygote with a multicellular organism is the same: a zygote necessarily is one-celled, and so cannot develop into a multicellular organism in a way that preserves numerical identity.24

Van Inwagen elaborates on this argument in a manner that helps to explain why he considers being one-celled an essential property. He claims that the zygote’s life, its “vast assemblage of metabolic

24 Peter van Inwagen, Material Beings (Ithaca, NY: Cornell University Press, 1990), pp. 152-153.

30 processes” orchestrated by its DNA, is no longer unified in a two-celled embryo. According to van

Inwagen—who cites no biological evidence in his favor—fission disrupts this coordinated activity and so renders impossible the continuity of life.25 Although series of fissions eventually may result in coordinated biological activity, this will differ in kind and scope from the activity that is the life of a zygote.26 We can distill from van Inwagen’s explanation that changes in the kind of being that exists preclude human development from preserving identity.

Thomas Aquinas raises a kindred problem for the whole process of embryonic development. As

Thomas sees it, there are three fundamental types of biological beings: vegetative beings, which grow and feed but do not move; animal beings, which move and use their senses; and intellectual beings, which can think. Higher beings are capable of engaging in the activities of the lower beings but not vice versa. Beings of each order always differ in kind; a fortiori, they always differ numerically. Now Thomas holds that during human development the embryo is successively a vegetative being, an animal, and an intellectual being. More precisely, he holds that a vegetative embryo is succeeded by an animal embryo, which in turn is succeeded by an embryo with cognitive abilities. Because each embryo is different in kind from the next, there is no possibility of numerical identity throughout human development. There are instead three numerically distinct beings.27

While one may wish to modify Thomas’s arguments to account for later developments in embryology, his line of thinking remains popular today, as van Inwagen’s argument suggests. Indeed,

25 Notably, van Inwagen does not raise the possibility that a zygote is a phase sortal of a human organism. For the time being we shall let this pass. 26 Van Inwagen, p. 153. 27 See, e.g., Summa contra Gentiles (SCG) II, c. 89, n. 11.

31 as Eric Olson points out, many contemporary champions of psychological definitions of personhood either implicitly or explicitly support views similar to Thomas’s in at least one respect.

Such philosophers hold that humans transition from being non-persons to being persons upon acquiring some critical psychological feature. On this view, like Thomas’s, there is not numerical identity throughout early human development.28

While his embryology is antiquated in its details, Thomas’s argument nonetheless reflects metaphysical concerns similar to those found in van Inwagen and other contemporary philosophers.

If we acknowledge that certain properties define a mature organism or belong to it necessarily, it seems impossible to consider the mature and developing organisms to be the same in kind. Since disparity in kind precludes numerical identity, we are compelled to deny the numerical identity of mature and embryonic organisms.

These arguments from van Inwagen and Thomas are not decisive. There are reasons to view numerical identity through development as continuous rather than discontinuous. It seems that there is one uninterrupted process unifying the different stages of development. We often speak of our childhood or infancy as part of our lives despite the large cognitive and physiological chasms that separate adults from young children and infants. This is in part because our later cognitive and physiological developments appear to be changes within those infants and children rather than changes to their identities. Moreover, the orchestrated processes of metabolic activity mentioned by

28 Eric Olson, The Human Animal (New York: Oxford University Press, 1997), pp. 74-77. Note that a philosopher could distinguish the criteria for personhood from the criteria for human identity. That is, one might say that the criteria for being the same human individual are not the same as the criteria for being the same person. A proponent of this view might differ substantially from Thomas by holding that there is numerical (but not personal) identity throughout early human development.

32 van Inwagen take place in accordance with the function of the same DNA from zygotic life all the way to adulthood. It is because of the way the zygote’s life unfolds that the adult’s life unfolds in certain determinate ways as well.

Proponents of continuity may also recur to the metaphysics of self-change to explain their view.

They may note that there is an active potency in the juvenile organism to make the adolescent or adult organism F, even though the juvenile itself is not-F. For example, there is an active potency in the caterpillar to make itself a flying animal even though it currently cannot fly. Correspondingly, the caterpillar is capable of being changed into a flying animal; it has a passive potency to be made a flyer. Therefore, even though the caterpillar does not fly, it is essentially different from other creatures that do not fly: it can change itself from a non-flying animal into a flying animal. The same observation holds, mutatis mutandis, for all other organisms that undergo radical developmental change.

The foregoing retorts do not defeat the objections raised by van Inwagen and Thomas. More needs to be said about the relationship of potencies to seemingly essential properties, such as flying in butterflies and thinking in humans. That discussion must wait until Chapter 5. Nonetheless, the responses indicate that there is a case to be made for numerical identity throughout significant developmental changes.

Repeated self-change poses another apparent obstacle to numerical identity over time. Throughout an extended, far-reaching series of self-changes, it seems that there is no single underlying subject of the changes. For the matter of the developing subject changes almost entirely; in human

33 development, for instance, little or nothing at the cellular level remains from conception to adulthood. In such an instance it would seem that there is no single, enduring substrate that possesses the various properties ascribed to the individual at different times. There is instead a host of differing, historically connected substrates, some of which share few or no parts with one another. Because there are many substrates, there are many individuals. In this case, development is incompatible with numerical identity.

As with the first problem arising from development, this problem receives treatment in the works of

Thomas Aquinas. In this instance, however, Thomas argues that repeated, incremental changes in the individual’s matter do not result in a numerically distinct substrate or a numerically distinct individual. Ignoring the details of his argument for the time being—we shall return to them in

Chapter 3—Thomas states that an individual and its material substrate may remain the same even without retaining the same constituent particles.29

On this issue van Inwagen also maintains that there is often numerical identity through a change of substrate. He considers a case in which the interacting particles that constitute a life are gradually replaced so that the resulting life activity involves none of the original constituents. Is the resulting life numerically the same as the original life? According to van Inwagen, in many cases the answer is

“yes.” There is a sort of “spatiotemporal and causal continuity” that undergirds the identity of such a life through time. As he sees it, this sort of continuity is typically—but not always— sufficient for the diachronic identity of an organism.30 It appears, however, that van Inwagen has no general

29 In II Sent., d. 30, q. 2, a. 1. 30 Van Inwagen, p. 149.

34 principle or argument on which to base this claim, for he admits that he cannot supply necessary and sufficient conditions for the diachronic identity of an individual life.31

Thomas and van Inwagen’s view is highly controversial. Both “extreme” and “moderate” metaphysicians can find something to dislike therein. On the more radical side of the spectrum, mereological essentialists, who maintain that no object can survive the loss of any part, will reject

Thomas and van Inwagen’s view outright. Less radical theorists will note that the proposal occupies the extreme opposite of mereological essentialism: it denies that any quantity of particles must endure for an individual to survive through change. If continuity of material parts is not needed to ensure diachronic identity, then what is? Thomas and van Inwagen must supply some answer to secure the credibility of their position.

This puzzle and the problem discussed just before it reveal that self-change poses a significant challenge for a theory of diachronic identity.

Explanatory Power A metaphysician, having solved the problems described above, might claim that he has produced the definitive theory of diachronic identity. However, he would be wrong. A theory must simplify the explanation of many difficulties by recourse to a set of common, fundamental principles. A congeries of answers to puzzles fails in this respect. Furthermore, a successful theorist will present his system’s powers and limits, what it can and cannot explain.

31 Van Inwagen, p. 158.

Working out a theory of identity thus requires some discussion of the nature of explanation.

Specifically, there are three topics to address. First, it is necessary to specify the kind of explanation required. This task encompasses a description of the phenomena to be explained and the means of explaining them. Second, some defense of the possibility of explanation is needed. The type of explanation sought may be impossible, or possible only in restricted circumstances. Finally, if explanation is possible, the extent of the explanation must be described. In other words, it is necessary to establish the limits for any possible explanation of diachronic identity. These limits may touch upon both the unity of explanation—perhaps many principles are needed for many problems—and the point at which explanation must stop. Thus, a complete theory of diachronic identity will furnish principles underlying its conclusions, to the extent that such principles may be discovered.

Logically, the first task is determining what kind of explanation is needed. Once this matter is settled, we can inquire whether this sort of explanation is possible, and, if so, under what conditions.

Trenton Merricks has provided a useful distinction that addresses this first matter. He identifies two modes of explaining identity, epistemic and ontic. Epistemic explanations present the features by which we correctly re-identify objects across times. For example, an epistemic explanation of how I identify my father would include his facial features, his posture, and his gait. The features that underlie such a re-identification Merricks terms evidence.32 Thus, explaining why I believe a certain man to be my father entails the presentation of evidence. This evidence, however, does not underlie my father’s identity; the facts on which we base our judgments of identity are not necessarily responsible for the actual continuation of identity. Rather, there may an ontic explanation of why my

32 Merricks, “There Are No Criteria of Identity over Time,” Nous 32:1 (1998), pp. 107-108.

36 father was the same man on Tuesday as he was three days before. Such an explanation would be given in terms of criteria, ontological facts or properties that underlie sameness through time. These criteria may be entirely unrelated to the evidence for a judgment of identity.

The sort of explanation needed for a theory of diachronic identity is ontic, not epistemic. The theory should specify what facts or properties, if any, guarantee that an object remains the same through change. Knowledge of how we correctly make judgments about identity is interesting but irrelevant to the theory.

It is also important to specify that the sort of ontic explanation desired deals with identity at the level of a natural kind, or perhaps at some more inclusive genus. This stipulation may seem odd, for this inquiry is concerned primarily with numerical identity through time. However, there is no contradiction between the two desiderata. The ideal explanation would provide a common criterion or set of criteria that governs diachronic identity for all individuals within a kind. For example, some common criteria might determine the diachronic conditions of numerical sameness for all individual humans or all individual animals. Thus, the criteria would be general, applying to the kind or some broader group, yet still determinative of numerical diachronic identity.

Merricks’s taxonomy requires a further subdivision of ontic explanation. Explaining the identity of an individual could proceed by two methods. The first and more commonly attempted method is a reductive analysis. This method analyzes identity in terms of a second phenomenon, such as spatiotemporal continuity. For example, according to the Humean view, identity is nothing more

37 than a “succession of parts, connected together by resemblance, contiguity, or causation.”33 The second method, in contrast, attempts something more modest. It analyzes the diachronic identity of a particular object in terms of the identity of other objects. For example, one might explain the diachronic identity of the whole in terms of the persistence of its parts or vice versa. In all such attempts the final analysis does not reduce diachronic identity to another phenomenon but instead explains a particular instance of diachronic identity. Thus, there is no explanation of diachronic identity tout court.

One may object that this second approach does not yield a theory of diachronic identity but rather a series of incomplete and disconnected theories. That may indeed turn out to be the case, but it does not follow necessarily. Instead, there may be analyses of identity that apply to large and interesting groups, say all natural kinds or all substances. Even a theory limited to these groups would be nontrivial. Furthermore, it would be no worse off than other non-reductive theories, which still manage to generate powerful and unexpected conclusions despite their limits.

Some form of ontic explanation must back up a theory of identity over time. Is such explanation possible? Merricks has argued not. He begins by pointing out that criteria must be informative; they must not presuppose the identity that they establish. For this reason an appeal to “sameness of essence” will not explain diachronic identity—not, at any rate, if sameness of essence is explained in terms of identity.34

33 David Hume, A Treatise of Human Nature, ed. David Fate Norton and Mary J. Norton (New York: Oxford University Press, 2005), 1.4.6, p. 166. 34 Merricks, “There Are No Criteria of Identity over Time,” p. 107.

Perhaps, Merricks suggests, we can analyze identity over time by further analysis of identity or existence at a time. Yet he argues that this attempt quickly fails. An analysis of identity in terms of indiscernibility succeeds only if it includes “individual essence-like” properties. This analysis, however, is uninformative. Similarly, an analysis of existence at a time does not yield criteria of identity on Merricks’s view. He construes existence at a time as “existing when a time is present”—a curious construal, but one that shall pass for now. Merricks rightly remarks that it is uninformative to claim that diachronic identity amount to existing when t is present and existing when t' is present.35

Merricks then considers a second popular approach to analyzing identity over time: analyzing diachronic identity for a particular kind, such as composite objects. He contends that this kind- relative approach also must fail. Kind-relative identity, he claims, is not susceptible to informative analysis. The analysis of atom identity over time, for example, amounts to being an atom and being identical over time with an object O. Such an analysis clearly is uninformative. If it is the best available, then there is no hope for kind-relative identity.36

Merricks, however, has created a straw man in this case. No philosopher—and probably no layman—would provide these sorts of kind-relative analyses of identity. It is far more likely that a layman would say that an atom at one time is identical with an atom at another time if the two atoms share some feature or part in common. For example, he might claim that the first atom and the second are the same if and only if their nuclei are numerically identical. A philosopher might offer a

35 Merricks, “There Are No Criteria of Identity over Time,” p. 110. 36 Merricks, “There Are No Criteria of Identity over Time,” p. 110.

39 more metaphysical answer. If he were a substratum theorist, taking substances to consist of bare particulars and tropes or properties, he might say that O and O* are identical if they have the same bare particular in common. A bundle theorist, positing that atoms are simply bundles of tropes, might agree that O and O* are identical if some or all of their tropes are numerically the same. Each of these answers is informative in a way that Merricks’s answer is not.

Merricks could retort that these analyses fail to yield criteria of identity because each analysis employs the concept of identity. There are two ways to understand this criticism. The first is that the proposed analyses presuppose that the objects in question, O and O*, are truly identical. In fact, the analyses do no such thing. Consider again the analysis of an atom in terms of its physical or metaphysical constituents. In this case I have suggested that the numerical identity of the atom’s parts, bare particular, or tropes may explain the identity of the atom. An analysis along such lines offers some new information, for it tells us that the identity of the whole depends on the identity of certain constituents. Notably, in such an analysis we do not presuppose the identity of the wholes, though we do, of course, presuppose the identity of parts. As a result of this second presupposition, however, a second objection may arise that we still have not eliminated all reference to identity from the analysis. Yet if we have given up on an analysis of identity simpliciter—as Merricks has—then this should not worry us. It may not be possible to analyze all identities, but perhaps it is possible to explain the diachronic identity of some objects in terms of the diachronic identity of other objects.

Such an analysis is limited but still fruitful.

Thus, it seems possible to offer some criteria of identity along the following lines. The identity of an object O can be discussed in terms of identity of its constituents. This is not an analysis of identity

40 tout court, but rather an analysis of the identity of a complex object. Philosophers often have adopted this approach to explain personal identity. A person is held to be the same as long as she has the same memories, or brain, or some other constituent. Setting aside the question of the correct analysis of personal identity, this appears to be a promising strategy. This strategy is feasible so long as the identity of the part is sufficient for the identity of the whole. Thus, pace Merricks, there are criteria of identity.

Explaining the diachronic identity of wholes in terms of the diachronic identity of parts raises two related questions. First, how far can the explanatory process go? One may wonder whether there are also criteria for diachronic identity of parts of a composite object, provided that these parts are composite. One may then wonder about criteria of identity for parts of the parts, and so on. If there are criteria of identity for parts, then the explanatory process could continue down to the level of indivisible constituents. The possibility of such progress leads to the second question: are there means of eliminating the concept of diachronic identity altogether from the analysans? In other words, is it possible to offer criteria of diachronic identity, whether of a composite object or an indivisible object, in terms that exclude the concept of identity?

The answer to the first question turns on the meaning of the term “part.” Here “part” may take on either of two senses. First, the term could mean a physical proper part, such as an appendage, cell, or atom. Alternatively, “part” may mean a metaphysical part, a constituent such as a bare particular, a universal, or an Aristotelian form. The choice of one option over the other has important consequences for the broader theory of diachronic identity. While I will not argue definitely in favor

41 of either option at this point—I will do so in Chapter 3—I will now discuss some of the limitations on each.

Explaining the identity of wholes in terms of the identity of physical parts faces two chief limitations. First, most physical parts are composed of simpler physical parts, and these parts in turn are composed of yet simpler parts, and so on until absolutely simple parts are reached. As parts become simpler, however, they generally become more transient, so that a putatively enduring object loses some of its simplest parts almost constantly. While an appendage remains, the cells within the appendage cycle in an out, and the molecules within these cells enter and exit even more frequently.

Accordingly, only relatively large physical parts will persist long enough to explain the persistence of wholes, and the persistence of these parts will not be explicable in terms of the persistence of yet smaller parts. Second, as parts grow simpler, they also become less relevant to an object’s natural kind. Although a protein may occur only within one biological species, the amino acids within that protein will appear in many species, and the atomic constituents of the protein will occur in non- living objects as well. When parts do not constitute an object as a member of a natural kind or follow from the object’s being a certain kind, they no longer serve to explain the generic identity of that object (the identity as member of kind F) over time. Such parts, therefore, would not be relevant to numerical identity, either. Thus, only kind-relevant, enduring physical parts—a relatively small category—are candidates to explain the persistence of wholes.

In contrast to physical parts, metaphysical parts typically have no constituents. Bare particulars, universals, tropes, Aristotelian forms, and other candidates typically are not composites.37 Therefore, these parts represent the ne plus ultra for criteria of identity over time. For instance, if one reduces the criteria of diachronic identity for a substance to the identity over time of a bare particular, one can go no further. However, some metaphysical parts suffer from the same limitations as physical parts: they are “disposable” or irrelevant to an object’s generic identity and potentially to its numerical identity as well. Such metaphysical parts will not suffice to ground the diachronic identity of the whole object. Instead, only “individual essence-like” parts, to use Merricks’s descriptor, will suffice to explain diachronic identity. Thus, if one opts for metaphysical parts over physical parts, the explanation of an object’s diachronic identity will terminate with some “individual-essence-like” trope, universal, or form. Contra Merricks, this would constitute an informative criterion of identity, for in positing such parts we make two claims: 1) objects or groups of objects possess such essential metaphysical parts, and 2) the essential metaphysical parts are of one sort rather than another, e.g., a trope rather than a universal.

The second question asks whether the analysis can reduce identity to some other phenomenon. The straightforward answer is no. The primary candidate phenomenon for such an analysis, spatiotemporal continuity, is entirely inadequate for this purpose. As David Oderberg has shown, an analysis in terms of spatiotemporal continuity fails because the analysis always contains some reference to persisting places, which in turn must derive their identities from persisting objects.

Thus, the concept of identity remains in the analysis, if only obscurely.

37 Some putative metaphysical constituents may be divisible into further parts. See, for example, David Lewis’s and David Armstrong’s exchange on structural universals, or universals composed of other universals.

Given the failure of the most promising analysis of identity, it is reasonable to agree with Oderberg that identity is “primitive.” As he explains, however, there are two ways of understanding what it means for identity to be primitive. He describes these two ways thus:

The right way is to take the phenomenon of identity per se to be primitive. In other words, there is no way of defining identity across time in other terms: it is a basic, unanalyzable phenomenon. The wrong way is to take it as meaning that the identity of specific material substances themselves is primitive: in other words, it would be incorrect to claim that when it comes to identity, nothing further can be said about why it is that an object of a certain kind, existing at a given time, is numerically identical to an object of a certain kind identified at a later time; or why an object at one time is identical to this object rather than that object at a later time.38

Following Oderberg, I take identity to be primitive. In other words, I deny that one can analyze diachronic identity in terms of any other phenomenon that does not presuppose identity. On this point I am in agreement with Merricks as well. I also concur with Oderberg’s claim that the primitiveness of identity does not preclude limited explanations of diachronic identity in certain cases. Such explanations will always retain some reference to the concept of diachronic identity, perhaps merely an implicit reference. Nonetheless, these explanations may be informative when the analysans introduces some new entity O whose identity over time underlies the diachronic identity of the object of interest.

The foregoing conclusions about explanatory power establish three requirements for a theory of diachronic identity. First, and most fundamentally, the theory must offer an explanation of identity over time, for such an explanation appears to be possible. Second, the explanation provided must be ontic rather than an epistemic. Finally, the theory must trace the identity of objects down to the

38 David Oderberg, “Hylemorphic Dualism,” p. 77.

44 most basic explanatory criteria, namely the basic parts underlying the identity of wholes, whether those are given in physical or metaphysical terms. Chapters 3 and 4 of this work will attempt to provide a theory that satisfies these requirements.

Conclusion There are still many outstanding problems in the philosophy of diachronic identity. In fact, it appears that none of the prominent classic and contemporary challenges has been put to rest definitively. Furthermore, previously overlooked difficulties with self-change reveal a significant lacuna in the contemporary literature. Lastly, there is extant conflict over the type of explanation that a theory of diachronic identity must provide for its conclusions. A successful theory, then, must address each of these difficulties in a thorough and compelling fashion.

CHAPTER 2: CURRENT THEORIES OF DIACHRONIC IDENTITY AND THEIR SHORTCOMINGS

The previous chapter set forth the requirements for a successful theory of diachronic identity. This chapter will investigate whether any of the theories on offer today satisfy these requirements. As I mentioned in the last chapter, these theories belong to two main camps: endurantism and perdurantism.

There has been enough controversy over the definitions of endurantism and perdurantism that I should provide and defend my understanding of each theory. My attempt to define the theories will proceed by contrast: I will focus on the fundamental claims on which endurantism and perdurantism are opposed. In the course of this discussion, I will also distinguish the chief variants of each theory.

There are enough permutations of endurantism and perdurantism that an exhaustive taxonomy lies beyond the scope of this work. However, identifying the chief strands of each theory will allow for an assessment of the strength of the most common positions on identity over time.

The Fundamental Distinction For all the literature on diachronic identity, there are not widely accepted definitions of endurantism and perdurantism. In fact, there is a modest body of literature proposing various, often conflicting definitions for the theories. Consequently, I must clarify my interpretations of endurantism and perdurantism in relation to these competing definitions. In what follows, I will argue that Ted Sider has presented the most acceptable definition of perdurantism to date, and Trenton Merricks has done the same for endurantism. It is perhaps too much to hope that philosophers will find my

46 arguments in favor of these definitions conclusive, but at the very least I intend to supply reasons for adopting these definitions over their chief rivals.

Despite the lack of settled definitions, there is some very general agreement about the distinction between the two theories. To explain this common ground, it will be helpful to offer an “intuitive” presentation of the theories. By this I mean a rough sketch of the pre-philosophical and quasi- philosophical motivations for each theory as well as some non-technical descriptions of the central claims of each view. These preliminary remarks will also allow for the introduction of some specialized terminology that I will explain with more precision later. For the time being, both my explications of the theories and my use of terminology will be broadly illustrative rather than definitive. In other words, I intend to discuss in a general way views to which most endurantists and perdurantists subscribe. Almost all theorists in both camps, however, will wish to add many details to this sketch, and a (hopefully very small) minority will find it altogether unreflective of their views and motivations.

Both endurantists and perdurantists hold that everyday objects—trees, frogs, humans, and the like— persist through time. For both camps diachronic identity is a genuine phenomenon. Though seemingly trivial, this basic agreement distinguishes them from philosophers who deny that anything does or can persist. Moreover, both groups acknowledge that objects change; some things pass from beige to red, from calm to furious, or from naïve to guileful. What separates endurantists from perdurantists is their metaphysical picture of how change occurs. More precisely, the difference between the two groups lies in their views of how certain changeable entities exist through time. In

47 general, the disagreement concerns only those entities called ‘objects’ or ‘substances’ in most ontologies. The identity of such entities as properties, actions, and events is not at stake in this dispute.

Perdurantists, on the one hand, contend that changeable objects are composed of a series of

‘temporal parts’ (also called ‘slices’ or ‘stages’), each of which exists only at one time. We can picture these temporal parts distributed across a continuum of time much like a chain of paper dolls laid out in space. To illustrate this scheme, Figure 1 on the next page depicts part of Socrates’ career as the perdurantist understands it. Socrates’ life is composed of multiple temporal parts, and each of these temporal parts includes all his spatial parts at a given instant. T1, for instance, may be a stage from his youthful disputations with Parmenides. T1 would thus encompass all of young Socrates’ physical parts (including a full head of hair) and properties at that instant. T2—a stage dating to a moment in the feast of the Symposium for the sake of this illustration—would include the mature Socrates and all his parts and properties (such as being full of wine) at that time. Finally, T3—Socrates in the last moments of his life—would again include all his physical parts and properties (such as poisoned with hemlock) at that instant.

A series of temporal parts linked together by an appropriate identity relation is a ‘space-time worm’ or just a ‘worm.’1 Referring to the figure again helps explain the choice of this term. The space-time worm, like a chain of paper dolls, comprises a series of segments, namely the worm’s temporal parts.

1 Later in this chapter I will briefly discuss perdurantists’ views on the nature of the diachronic identity relation.

As we shall see later, perdurantists differ on whether we ordinarily refer to worms or to temporal parts—worm segments— in everyday speech. Proponents of the view that we usually refer to worms are called worm theorists, and proponents of the view that we usually refer to temporal parts are called stage theorists.

Socrates

T1 T2 T3

Temporal parts or stages of Socrates

Figure 1: Socrates through Time on the Perdurantist View

It is now easy to outline the endurantist position in contrast to perdurantism. Endurantists deny that objects have temporal parts. Therefore, the paper doll image is entirely misleading for the endurantist. A persisting individual has no temporal parts or stages, the endurantist claims, so at any given instant the entire individual is ‘wholly present.’ This contrasts with the perdurantist view, on which only a temporal part of an individual is present at given instant

With this basic outline of the theories in place, we can now cover some additional uncontroversial claims about the theories in more technical terms. In general, agreement about the definitions of perdurantism and endurantism concerns primarily what each theory does not endorse. Articulating these differences requires a little more explanation of temporal parts. In the crudest terms, which I will refine shortly, a temporal part x of an object O exists only at a specified time t and includes all parts of O and only parts of O existing at t (here ‘parts’ refers primarily to spatial parts, though a temporal part would include metaphysical constituents of O as well). Here ‘time’ may refer either to an instant or to an interval.2

Perdurantists deny that an object lacking temporal parts—assuming that such a thing can exist— could alter with respect to its parts or properties. An object that changed over time without metaphysical subdivision, the perdurantist holds, would possess contradictory properties. On the perdurantist’s view, for instance, an individual who is beardless as a boy and bearded as an adult would possess incompatible properties if he had no temporal parts. That is, the very same entity would be both beardless and bearded if there were no temporal parts. As mentioned in Chapter I, this prima facie contradictory state of affairs leads Lewis to formulate the “problem of temporary intrinsics.” According to Lewis and other perdurantists, if someone claims that one and the same individual was both bearded and beardless, his statement is correct only under this interpretation: some individual space-time worm has one temporal part that is bearded and another distinct temporal part that is not bearded. Furthermore, as Lewis’s response to the problem of temporary

2 Most perdurantists develop their theories around instantaneous temporal parts, but there are philosophers who allow temporal parts while denying that they can be instantaneous. See, e.g., Dean Zimmerman, “Persistence and Presentism,” Philosophical Papers 25 (1996), pp. 115-26.

50 intrinsics contends, there is no satisfactory way for an endurantist to address this incompatibility. On

Lewis’s view, the endurantist must either relativize property possession to times or she must embrace presentism, the doctrine that no objects exist except those that exist at the current moment of time. Neither of these solutions is attractive to the perdurantist, who thus denies the possibility of intrinsic change without temporal parts.

Endurantists, on the other hand, deny that objects that persist through time have temporal parts. An endurantist holds that the phenomena of persistence and change are explicable without reference to temporal parts. For the endurantist, the wholly present individual is the direct bearer of different properties and the direct possessor of different physical parts. There is no mediation by temporal parts. Whereas the perdurantist would say that Socrates-at-T1 argued with Parmenides, and Socrates the space-time worm can be said to have argued only in virtue of what Socrates-at-T1 did, the endurantist would dismiss the need for any such being as Socrates-at-T1. Instead, the endurantist would claim that Socrates (simpliciter) argued with Parmenides at t1. Furthermore, the objections that perdurantists raise to change in objects without temporal parts are, for the endurantist, metaphysically toothless and require semantic explanations at most. While more can (and will) be said about endurantism, further discussion requires investigations of semantic explanations of change.

Perdurantism The preceding negative formulations of each theory suggest substantive positive commitments.

However, philosophers articulate these commitments in very different and often incompatible

51 manners even when they belong to the same camp. Some accounts locate the distinction between the theories in the way that they treat property possession; others turn on the different ways in which perdurantism and endurantism view temporal parts. Here I will argue that the latter distinction is fundamental and allows for the most cogent exposition of perdurantism.

A good starting point for this review of definitions is the minimalist formulation provided by Mark

Heller. He states that perdurantism (which he calls “four-dimensionalism”), in its most basic sense, holds that “persisting objects extend over time in the way that they extend over space.”3 Heller’s definition of perdurantism, though compact, leaves much to be desired. The analogy with space is vague in multiple ways and thus unhelpful. An initial problem is that acknowledging that material objects are spatially extended does not commit one to a particular spatial mereology. Philosophers who all admit spatial extension offer incompatible accounts of the part-whole relations of extended objects. Eric Olson, for instance, has denied that a human body contains hands or other physical parts though he acknowledges spatial extension.4 Thus, a perdurantist such as Heller first needs to clarify the role of space in determining parthood. Similarly, stating that an object extends through time does not outline a concrete ontology. A endurantist may agree that in some sense objects extend through time; that is, they persist. These objects have lives or ‘careers,’ and it can be said that they extend through time by existing at more than one instant. To distinguish perdurantism from endurantism, something more is needed.

3 Mark Heller, “Varieties of Four Dimensionalism,” Australasian Journal of Philosophy 71:1 (March 1993), p. 49. 4 Eric Olson, “Why I Have No Hands,” Theoria 61 (1995), pp. 182-97.

Fortunately, more robust formulations are available, at least for perdurantism. Ted Sider grounds the distinction between perdurantism and endurantism in his definition of temporal parts. Sider defines an instantaneous temporal part of an object y as follows:

“x is an instantaneous temporal part of y at instant t =df (1) x exists at, but only at, t; (2) x is a part of y at t; and (3) x overlaps at t everything that is a part of y at t. 5”

This formulation presents an instantaneous temporal part as an entity that includes all—and only all—of a temporally extended object for a moment of time.6 The temporal part includes all the spatial parts and metaphysical constituents of the extended object, so long as they exist at the time t.

Sider’s notion of an instantaneous temporal part allows him to define perdurantism in terms of the possession of temporal parts. On his view, a perdurantist holds that “necessarily every spatiotemporal object has a temporal part at every moment at which it exists.”7 Perdurantism thus amounts to embracing temporal parts as constituents of all objects.8 As noted previously, these parts may or may not be instantaneous in ‘temporal extent,’ but instantaneous temporal parts are the

5 Sider, Four Dimensionalism (Oxford: Oxford University Press, 2001), p. 59. According to Sider’s terminology, “Two objects overlap at a time iff something is a part of each [of them].” 6 Sider’s definition of ‘overlaps’ ensures that a temporal part does not include parts—spatial or otherwise—that its extended whole lacks. 7 Sider, Four Dimensionalism, p. 59. 8 To say that temporal parts are constituents is not to say that the parts are necessarily prior to the wholes that include them. Four-dimensionalism does not imply this claim.

53 norm among perdurantists.9 For a perdurantist, then, objects persist by having appropriately related temporal parts that succeed one another.10

Neil McKinnon reformulates Sider’s definition slightly to accommodate the possibility of perduring/enduring hybrids. To motivate this formulation, McKinnon asks the reader to envision a world where endurance is the norm, with one essential variation: the mereological sums of multiple objects existing at different times perdure. In other words, single objects endure, but groups of such objects may perdure. This world, which presupposes unrestricted composition and a tenseless theory of time, could include a perduring entity cobbled together from multiple enduring objects, such as

Oliver Cromwell, Benjamin Disraeli, and Tony Blair.11 If such a world is possible, McKinnon claims, one should redefine endurantism and perdurantism to allow for hybrids.

This hybrid theory seems to disregard the very motivation for the opposing views. Endurantism and perdurantism are opposed precisely because they are different explanations of how objects acknowledged to exist by both parties persist through time. If endurantism and perdurantism recognize different sorts of objects altogether, then there is no longer a controversy about identity; instead, there is a dispute about entities—the denizens of the universe. In this vein, an endurantist

9 For more nuances on the nature of temporal parts, see Ryan Wasserman, “Framing the Debate over Persistence,” Metaphysica 5 (2004), pp. 69-73. Wasserman argues that perdurantists can take one of two views on the nature of temporal parts. “Strong perdurantists” hold that a single temporal part may span any temporal interval of an object’s existence, even a discontinuous interval. “Moderate perdurantists,” on the other hand, deny that temporal parts can span any arbitrary interval, though these theorists acknowledge that objects do in fact have instantaneous temporal parts. This distinction will not affect the objections to perdurantism raised later in this chapter. 10 The nature of this relation is discussed later in the chapter. 11 Neil McKinnon, “The Endurance/Perdurance Distinction,” Australasian Journal of Philosophy 80.3 (September 2002), pp. 294-96.

54 should simply respond to the endurantist/perdurantist hybrid theory that the endurantist component correctly characterizes identity and the perdurantist component describes a relation other than identity. The perdurantist, in turn, should object to the hybrid theory for suggesting that anything at all endures. In short, the hypothetical world of the Cromwell-Disraeli-Blair object is likely to face objections from most, if not all philosophers. So it seems that McKinnon’s accommodation of such a hybrid theory is otiose.

This brief survey of definitions of perdurantism suggests that Sider’s is foundational. We should understand perdurantism as the thesis that objects persist in virtue of having temporal parts, as defined above. There is some disagreement about a central feature of temporal parts—namely, whether they are instantaneous in extent or not—but little conflict otherwise. Furthermore, the proposed reformulations of Sider’s definition are modest and weakly motivated. Consequently, I will embrace Sider’s definition of perdurantism and proceed to search for a similar positive definition of endurantism.

Endurantism Because Sider provides the best definition of perdurantism, it is reasonable to turn to him for a definition of endurantism as well. When attempting to explicate endurantism, however, Sider states that he cannot furnish a definition of the theory. He attempts to find a positive thesis behind endurantism but fails to do so. According to Sider, it is impossible to articulate a sense of whole presence—allegedly the core concept of endurantism—that is plausible and distinctive of endurantism. For instance, he remarks that an endurantist cannot interpret whole presence to be the

55 claim that anything that is part of an object O at time t is always part of O; this view precludes the gain or loss of parts. Other definitions are similarly too restrictive or otherwise uninformative.

Consequently, Sider characterizes the theory negatively, as the rejection of temporal parts.12

The shortcoming of Sider’s negative definition is that it leaves the positive commitments of endurantism unintelligible. Of course, the theory may in fact be devoid of any comprehensible positive claims; however, I do not believe that this is the case. Rather, I think that contemporary endurantists have for a variety of reasons neglected to articulate their theories of identity in terms of a full-blooded ontology. This deficiency prevents today’s endurantists from making substantive claims about whole presence, and it hinders them from identifying any other positive commitments of endurantism.

Because I will elaborate on these shortcomings further below, one brief example will suffice to illustrate this point for now. Peter van Inwagen, a prominent endurantist, defines his metaphysical views negatively: “the concept of a temporal extent does not apply to...any...object that persists or endures or exhibits identity across time.”13 Of course, he also affirms that a persisting object is identical across times without the mediation of temporal parts, but he does not offer an ontological explanation of this phenomenon (presumably none is needed on his view). Instead, he addresses an array of problems about identity statements. Thus, van Inwagen confines the constructive work of his theory to semantics. This approach, which is typical in endurantist writing, reflects the

12 Four-Dimensionalism, pp. 66-68. 13 “Four Dimensional Objects,” Noûs 24 (1990), p. 252.

56 unfortunate assumption that endurance needs no ontological explanation; this assumption indicates why endurantism often seems ontologically hollow.

Despite the thinness of today’s endurantist ontologies, at least one endurantist philosopher has stated a positive commitment of endurantism clearly. Merricks presents a distinction that I embrace: endurantists claim that objects possess properties immediately, while perdurantists argue that objects possess properties derivatively, via stages.14,15 Here ‘immediate’ means ‘without the mediation of temporal parts.’ Merricks also remarks that perduring entities exist “derivatively” by having temporal parts that exist at certain times, but enduring entities exist “nonderivatively” (are wholly present). In short, he agrees with Sider that the critical ontological distinction between the two theories concerns temporal parts. However, he goes beyond Sider to explain how this difference includes an affirmation about endurantism. According to Merricks, the endurantist claims that an object that persists through time has its properties directly or immediately; the notion of a temporal part is superfluous to the endurantist. The perdurantist, in contrast, believes that a persisting entity

(a space-time worm), cannot have properties directly; it can possess them only in virtue of having a temporal part that directly possesses them.

Merricks’s formulation alludes to but does not explicate the concept that is seemingly most central to endurantism, namely whole presence. Nonetheless, I believe that he neatly captures a core

14 “Endurance and Indiscernibility,” pp. 166-67. 15 In anticipation of further discussion of the varieties of perdurantism, I should add that some philosophers believe that the objects of ordinary discourse are in fact temporal stages. On this view, objects of ordinary discourse possess temporary intrinsic properties immediately.

57 positive thesis that makes endurantism appealing. Endurantists defend—or should defend—an ontology of direct property possession, which can be expressed as follows:

Direct property possession (DPP): A persisting object possess its temporary intrinsic

properties immediately—without the mediation of temporal parts.

Within this ontology temporal parts are unnecessary for property possession. This is a simpler ontology than perdurantism, to be sure, but it is not merely a negative theory.

DPP is a strength of the endurantist view because it allows us to preserve a powerful intuition.

Specifically, it enables us to hold that any object that changes is also the primary possessor of the properties with respect to which it changes. A theory that requires indirect property possession, such as perdurantism, results in a very counterintuitive view instead: it says that the changing object does not directly possess the properties in virtue of which it changes. For instance, when Mr. Schmitt’s brown hair goes gray, the endurantist can say without qualification that Mr. Schmitt’s hair color has changed. He previously had brown hair, and now he has gray hair. The perdurantist cannot make any such unqualified assertion; she must rather say that one temporal part of Mr. Schmitt had brown

58 hair, and a different temporal part had gray hair. Mr. Schmitt himself does not have a hair color so long as Mr. Schmitt is identified with a space-time worm.16

One might question whether this intuition is really so foundational. The analogous spatial case, in which an individual is said to possess a property in virtue of having a spatial part with that property, does not pose any problems. There is no difficulty saying that Mr. Schmitt is gray because his hair is gray, so why is there any obstacle to saying that Mr. Schmitt is gray-haired because one of his temporal parts is gray-haired? In response, it is important to note that the incongruity arises when one tries to describe any changes that Mr. Schmitt undergoes; in other words, adding a temporal dimension makes the parallel with space inadequate. We wish to say that Mr. Schmitt is the immediate—indeed, the only—subject of change when his hair goes gray. For perdurantists, however, he is not the immediate possessor of the properties with respect to which he changes. The dissociation is one of the primary costs of perdurantism.

Even if we are convinced by the line of reasoning above, we may wonder whether immediate property possession is in fact a necessary feature of endurantism. Could an endurance theorist reject direct property possession? I will address this matter in more detail when I examine the Aristotelian endurantism of Jeffrey Brower, which does just that. For the time being, I will mention that the only obvious way to avoid direct property possession is to introduce metaphysical constituents that either are temporal parts or function analogously to temporal parts, which Brower does. As this appears to

16 Sider acknowledges this problem for Lewis’s perdurantism in Four Dimensionalism, p. 98. As I discuss later in this chapter, perdurantists who favor the stage view, such as Sider, have a response to this objection.

59 be a move toward perdurantism, the default endurantist position is DPP. To be sure, an endurantist is not compelled to embrace DPP; however, without DPP endurantism loses much of its appeal.

As noted previously, literature on diachronic identity often locates the chief difference between endurantism and perdurantism in the doctrine of “whole presence.”17 Although this expression predates David Lewis, his use of it appears to have influenced many other philosophers.18

Unfortunately, he does not define the term. However, the following remark furnishes material for reconstructing his understanding:

Something perdures iff it persists by having different temporal parts, or stages, at different times, though no one part of it is wholly present at more than one time; whereas it endures iff it persists by being wholly present at more than one time. Perdurance corresponds to the way a road persists through space; part of it is here, and part of it is there, and no part is wholly present at two different places. Endurance corresponds to the way a universal, if there are such things, would be wholly present wherever and whenever it is instantiated.19

The comparison with universals is illuminating, for it suggests that whole presence means the

(possible) existence of a whole at multiple times without any division of that whole or difference in identity. Accordingly, an enduring object would be wholly present by existing at multiple times with strict identity (identity in every qualitative and mereological respect); this contrasts with the temporal parts of a perduring object, which are not strictly identical to one another.

17 See, e.g., Merricks, “Persistence, Parts, and Presentism,” Nous 33 (1999), pp.421-38; Peter van Inwagen, Material Objects (Ithaca, NY: Cornell University Press, 1990); Michael Rea, “Temporal Parts Unmotivated,” Philosophical Review 107 (1998), pp. 225-60. 18 Lewis, On the Plurality of Worlds p. 202. Most philosophers cite Lewis’s explication of whole presence even if they do not take it to be definitive. 19 Ibid.

Those who believe that the concept of whole presence can perform important philosophical work include Crisp and Smith, who define the two theories of diachronic identity in terms of whole presence: an endurantist says that an object that exists at more than one time is wholly present at each of those times, while a perdurantist denies that a persisting object is wholly present at any time.20 Markosian also has incorporated whole presence into his definition of three-dimensionalism.

On his view, an enduring object is wholly present at every moment of its existence. However,

Markosian explicates whole presence as the absence of temporal parts, so his understanding is entirely negative.21

Many philosophers, however, judge whole presence to be a dubious concept, and their concerns are well-founded when applied to prevailing understandings of whole presence. Most views of whole presence exhibit one of two flaws. On the one hand, they may place implausible restrictions on identity through time, as Lewis’ view does. Lewisian whole presence requires that enduring objects be strictly identical at various moments of time just as universals are identical across their various instantiations.22 On this view of whole presence, endurantism entails immutability.

20 Thomas Crisp and Donald Smith, “‘Wholly Present’ Defined,” Philosophy and Phenomenological Research 71:2 (September 2005), p. 319. 21 Markosian, “The 3D/4D Controversy and Non-Present Objects,” Philosophical Papers 23 (1994), pp. 243-249. 22 It is important to bear in mind that the analogy with universals breaks down easily, particularly as one considers the particular views of universals.

On the other hand, some conceptions of whole presence are so indeterminate as to be useless. For instance, a philosopher may state that an object is wholly present if and only if it does not persist by having temporal parts. David Oderberg, for example, says that an object is present as a whole at any instant in time; it is not simply a part of a greater object that is partially present at a given time but present at other times as well.23 Here Oderberg employs ‘whole presence’ as a shorthand term for

‘the denial of temporal parts.’ Although this phrase may spare the reader a few unnecessary words, it does not add to the conceptual apparatus of endurantism. Instead, it leaves perdurantists wondering what ‘whole’ endurantists are speaking of. Identifying the whole with the collection of parts at a given time t makes whole presence trivial: even perdurantists would agree that an instantaneous collection of parts is present in its entirety at a given moment. In contrast, equating the whole with the persisting object seems to return us to a familiar objection to endurantism, namely that objects gain and lose parts and therefore are not strictly identical wholes across time. To provide a nontrivial explication of whole presence, then, an endurantist must situate this explication within the context of gaining and losing parts.

Despite the general confusion over the nature of whole presence, I do believe this concept pinpoints a foundational difference between the major theories of diachronic identity. Crudely put, the endurantist believes that an individual is “all there” throughout the course of its existence; a perdurantist does not. As I have just noted, precisely what being “all there” means is unclear. In my view, the unarticulated foundation of endurantism, cloaked in the term ‘whole presence,’ is that objects persist through time in light of some metaphysical constituent or nucleus of constituents that

23 Oderberg, “Temporal Parts and the Possibility of Change.”

62 is strictly identical across time. The existence of this constituent underwrites direct property possession and the rejection of temporal parts.

As I will discuss later in this chapter, the metaphysical thinness of most endurantist theories prevents them from characterizing whole presence in any illuminating fashion. Consequently, there is no thought given to metaphysical constituents that might ground identity through time. Equipped with a robust metaphysics, however, an endurantist can articulate a theory of whole presence that sharpens the contrast between three-dimensionalist and four-dimensionalist ontologies.

Before concluding the discussion of definitions, it is also worthwhile to mention a dispute that does not mark a distinction between the two theories, namely the opposition of presentist and eternalist views of time. In brief, presentism holds that only things that exist at this moment truly exist, whereas eternalism holds that events and objects not existing at the present nonetheless do exist— just at other points in time. Otherwise put, the eternalist holds that past and future entities can be said to exist, but the presentist holds that this is false. Some philosophers, such as Merricks, have held that endurantism and eternalism are incompatible.24 However, Merricks’s claim relies upon a definition of endurantism that is inconsistent with eternalism, and other philosophers, both perdurantists and endurantists, have developed definitions of endurantism that are compatible with eternalism.25 Importantly, the definition of endurantism used here does not presuppose presentism.

In contrast, the definition of a temporal parts used in explicating perdurantism does presuppose

24 “On the Incompatibility of Enduring and Perduring Entities,” Mind 104 (1995), pp. 523-31. 25 See, e.g., Sider, Four Dimensionalism, p. 70; van Inwagen, “Four Dimensional Objects,” Noûs 24 (1990), pp. 244-55.

63 eternalism. Sider, however, has argued that an appropriate analogous definition can be crafted for a presentist framework. For the purposes of this work, I remain noncommittal on the relationship between these theories of time and theories of diachronic identity, and the following arguments will not presuppose any necessary pairings between the sets of theories.

Varieties of Perdurantism The heart of perdurantism is its four-dimensionalist ontology, the advocacy of temporal parts.

However, perdurantism admits of semantic variations with slight ontological differences. Here I will outline the two main varieties of perdurantism, stage theory and worm theory, to prepare for a later critique of the two views.

Worm theory is the older and more common of the strands of perdurantism. Proponents of this view claim that we refer to space-time worms as continuants, or the objects that persist through change. Thus, when saying ‘Tom is now tall after having grown last summer,’ one refers to a four- dimensional object that “stretches” from last summer (at the latest) through the present. Likewise,

‘Tom is now six feet tall’ refers to a worm. Recurring to Figure 1, the reader can see that a four- dimensional worm, such as Tom or Socrates, encompasses a number of temporal parts bearing various properties. In this case, the worm Tom possesses temporal parts occupying the ‘temporal space’ between last summer and the present. According to the worm theorist, in most ordinary, non- philosophical speech we refer to worms rather than temporal parts even though the latter possess properties directly.

The chief alternative to worm theory, stage theory, avoids some difficulties that arise in putative cases of overlapping or coincident objects.26 In these cases, allegedly distinct persisting objects share temporal parts for a particular duration. Among the classic examples is the well-known case of the statue and the lump of clay. According to some philosophers, when a statue is fashioned from a lump of clay, two objects—a statue and a lump—come to exist in one location. They argue thus because the statue does not share the historical properties of the lump (e.g., was shaped into a statue yesterday), and because the statue does not share the modal properties of the lump (e.g., could be non- statue-shaped). In such instances, worm theorists say that two distinct objects coincide; more surprisingly, they claim that as long as the statue exists there are two statue-shaped objects present: the statue and the lump.27

Although stage theorists, such as Sider, agree that the statue and lump are different space-time worms, they deny that we should count them as two objects when they overlap. In fact, Sider claims that in most cases of overlapping objects (if one accepts such cases) we only count or speak about a single object. This object is not a space-time worm but rather a temporal stage. Consequently, predications are about temporal stages of space-time worms. As he puts it, “[T]he objects we typically discuss, name, quantify over...are stages.”28 Consequently, he considers stages to be

26 My introduction of stage theory closely follows Sider’s exposition in Four Dimensionalism, pp. 188-91. 27 Four Dimensionalism, p. 189. 28 Four Dimensionalism, pp. 190-91.

65 continuants—a referent in most ordinary statements about identity over time—though an individual stage does not in fact continue or exist at multiple times.29

Sider insists that the underlying metaphysics for the stage and worm views is the same, and to large extent this is true. He accepts the existence of all the space-time worms that the worm theorist posits, and he embraces the theory of temporal parts. As previously noted, the main difference between the theories is semantic: the worm theorist contends that most ordinary talk concerns worms, whereas the stage theorist holds that most ordinary talk refers to stages.

However, Sider has to introduce an important metaphysical distinction to handle a large class of statements that would otherwise pose problems for the stage view: predications of past or future properties. To see how these are problematic, consider the statement “John was a clerk three years ago.” If ‘John’ refers to an instantaneous stage, existing only at the present moment, then this statement is not true on its face: the instantaneous stage was not anything three years ago.

To address the problem of past and future predications, Sider posits temporal counterparts, or past and future stages that stand in a special relation, the counterpart relation, to the present stage.30 The truth condition for past and future predications is that the present stage has a counterpart possessing

29 I follow Sider’s usage in terming anything a ‘continuant’ if it is (putatively) the referent of everyday statements about identity over time and an item over which we quantify. Sider believes that stages play these roles. 30 Here I omit any discussion of the conditions for two stages’ being counterparts. Sider remarks that it is the same relation used by worm theorists to unite stages of space-time worms, and there are many analyses proposed for this relation.

66 the appropriate property at the appropriate time. Accordingly, if John’s present temporal stage (or simply John, if we follow Sider to the letter) has a counterpart existing three years ago that was a clerk, then “John was a clerk three years ago” is true.31 Thus, stages have historical properties in light of non-historical properties possessed by their temporal counterparts. However, note that on this theory, it is false to say “I am identical to a young child” but true to say “I am identical to something that was a young child.”32

Although worm theorists and stage theorists disagree about semantics, they agree on the fundamental metaphysics of four-dimensionalism. Both parties acknowledge the existence of worms and stages. Accordingly, a worm theorist and a stage theorist could agree on every metaphysical detail of four-dimensionalism while parting ways only on semantics. In fact, both types of theorists could agree that identity over time is to be analyzed in terms of the same sort of relations (among stages or temporal parts), whether those are physical continuity, psychological continuity, or something else.33 Therefore, both strains of perdurantism will have almost all their metaphysical strengths and weaknesses in common, though semantic objections to one strain may leave the other theory untouched.

31 Four Dimensionalism, p. 193. 32 Four Dimensionalism, p. 196. 33 Four Dimensionalism, p. 194.

Varieties of Endurantism Proponents of endurantism tout it as the commonsense understanding of identity over time.

Endurantism has likely earned this title because its basic formulation proposes little in the way of novel metaphysics. In short, enduring objects persist through time without any exotic temporal parts or counterparts. These objects possess their properties immediately, without the need for intervening metaphysical entities.

This simple, clear formulation has its weaknesses. The puzzles discussed in chapter 1 require endurantists to elaborate on their semantics and metaphysics, and here paths diverge. There are at least five strands of endurantist thought: relationalism, adverbialism, Aristotelian constitution theory, taking tense seriously, and sententialism. The differences among these theories appear primarily in their responses to the problem of temporary intrinsics. Notably, the distinguishing features of these responses are semantic, though some ontological divides emerge as endurantists work out the conclusions of their semantic claims. Later in this chapter, I will argue that this fixation on semantics reveals a weakness in endurantist theories.

One noted endurantist view, espoused by Peter van Inwagen, attempts to avoid the problem of temporary intrinsics by relativizing property possession to times.34 Some critics of this approach dub it “relationalism” because—on their view—it treats monadic properties as relations. To understand the approach from the perspective of its advocates, recall that the problem of temporary intrinsics

34 Peter van Inwagen, “Four-Dimensional Objects,” Noûs 24 (1990), pp. 249-250.

68 states that it is contradictory for persisting objects to bear different properties at different times without further qualification. In response, van Inwagen posits that persisting objects have all their temporary properties relative to times. This claim has both semantic and metaphysical implications.

On the semantic side of the ledger, any locution ‘x has F’ is in fact shorthand for ‘x has F at t.’ On this “relationalist” view, a statement about x’s having F may (and must) always be explicated metaphysically in terms of its having F at some time or set of times. To take van Inwagen’s example,

Descartes is never simply hungry; rather, he has hunger-at-t1. This theory circumvents the problem of temporary intrinsics by replacing simple predicates (is hungry and the like) with time-indexed predicates (has hunger-at-t1). Therefore, it turns out that objects cannot have incompatible properties at different times; at any two distinct moments in time, an object necessarily cannot enter into relations with incompatible time-indexed properties.

A second view, adverbialism, differs from van Inwagen’s approach in using only semantic tools.

Adverbialists such as Sally Haslanger and Mark Johnston contend that a sentence such as ‘x is F’ should be explicated as ‘x is tly F.’35 This phrasing parallels everyday constructions such as ‘Tom is currently indisposed,’ with the added philosophical thrust that instantiating a given property is necessarily temporally delimited. The metaphysical outcome of this semantical solution is that instantiation is relativized to a time. Unlike the relationalist solution, adverbialism does not make properties into relations. However, it does claim that adverbially modified properties—being tly hot, for example—are more basic than ‘simpliciter’ properties, or properties without adverbial

35 Sally Haslanger. “Endurance and Temporary Intrinsics,” Analysis 49 (1989): 119-125, and Mark Johnston “Is There a Problem About Persistence?” Proceedings of the Aristotelian Society, Supp. vol. 61 (1987), p. 128.

69 modification. In other words, the adverbialist claims that ‘simpliciter’ properties are abstractions from adverbially modified properties, for only the latter are possessed by objects. Thus, the chief issue of adverbialism is a revisionist theory of property possession.

A third solution, also focused on semantics, advocates “taking tense seriously.” Trenton Merricks is the main proponent of this view, though Roderick Chisholm has developed another version as well.

Merricks’ proposal makes two central claims. First, one should accept that the lack of apparent contradiction in tensed statements—‘O was F’ and ‘O is not F’—signals the absence of a metaphysical dilemma. In other words, we should take the tensed statements of ordinary speech rather than the tenseless statements of formal semantics as a guide to metaphysical correctness. For instance, ‘Mr. Schmitt was brown-haired’ and ‘Mr. Schmitt is not brown-haired’ are unremarkable statements that we have no difficulty accepting pre-philosophically; they only begin to pose difficulties if we translate them to ‘Mr. Schmitt at t is brown-haired ' and ‘Mr. Schmitt at t' is not brown-haired.’ After this translation, we encounter a contradiction if, relying on the Indiscernibility of Identicals, we accept that Mr. Schmitt at t is brown-haired iff Mr. Schmitt at t' is brown-haired.

Although some philosophers believe that in this case philosophical semantics has exposed a problem that ordinary language overlooks, Merricks urges that we take ordinary language as our lodestar and try to determine where traditional semantics has strayed from the truth.

However, because ordinary speech does not have the resources to address the errors of a perdurantist approach, Merricks still believes that an endurantist must formulate a semantics of

70 change.36 This semantics will provide a proper explication of the problematic statements, that is, an explication that shows why these statements, correctly understood, do not lead to contradiction.

Merricks’s second claim is therefore that statements of the type ‘O at t is F’ are explicated as ‘O exists at t and is F.’ He further adds that being F at t amounts to being F when the time t is present.37 This explication allegedly has the advantage of defeating the argument from temporary intrinsics. For, according to Merricks, any interpretation of the argument that employs his understanding of property possession at a time will be unsound.38 Consequently, Merricks claims that his approach demonstrates why the problem of temporary intrinsics is in fact a pseudo-problem for the endurantist.

Yet another semantically oriented approach to explicating endurantism is sententialism. This view, proposed by David Oderberg, holds that temporal qualifiers are non-truth-functional operators on closed sentences. On this scheme, unqualified sentences about property possession (‘x is F’) are basic, and temporally qualified sentences are modifications of such basic sentences. In this respect, qualifiers such as ‘at t’ function similarly to de dicto modal operators. Furthermore, just as dropping the modal operator ‘possibly’ does not yield a valid inference, neither does dropping a temporal

36 “Endurance, Identity, and Indiscernibility,” pp. 170-71. 37 “Endurance, Identity, and Indiscernibility,” p. 183. 38 More precisely, Merricks claims that there are two possible readings of the argument from temporary intrinsics that incorporate his explication of ‘O is F at t.’ One explication results in a premise that the endurantist has no reason to accept, and the other explication generates an unsound argument. However, in his comments on the unsound interpretation, Merricks claims that “The object referred to by ‘O at t’ is bent” can be false while “O is bent at t” can be true. This seems to be the case only if one adopts a perdurantist ontology, in which ‘O at t’ and ‘O’ have ontologically distinct referents. See “Endurance, Identity, and Indiscernibility,” pp. 178-79.

71 operator.39 This allows Oderberg to solve challenges such as the problem of temporary intrinsics by denying the inferences that undergird such puzzles.

To address both synchronic identity and diachronic identity, Oderberg proposes two forms of temporal operators. Operators of the form ‘At t’ qualify synchronic statements, and operators of form ‘From t1 to t2’ qualify sentences expressing diachronic identity claims. Notably, Oderberg— unlike Merricks—does not believe that his semantic theory is a consequence of endurantism; rather sententialism is merely compatible with endurance.40

An exception to the emphasis on semantics is Jeffrey Brower’s “Aristotelian endurantism.” This theory turns to Aristotelian metaphysics to address the problem of temporary intrinsics. On

Brower’s view, a metaphysics of constitution furnishes the material for explaining change. Enduring objects are compounds of form and matter, or a “complex organizational property” and “stuff” (in the philosophical usage) in Brower’s view.41 Such compounds themselves can temporarily constitute larger wholes, known as ‘accidental unities,’ by acquiring temporary intrinsic properties. Accordingly,

Socrates the individual constitutes part of the whole seated-Socrates when sitting and part of the whole standing-Socrates when standing. In both cases, Socrates possesses the property of seatedness or standing derivatively, and the accidental whole possesses these properties directly. In this respect,

39 “Temporal Parts and the Possibility of Change,” p. 698. 40 “Temporal Parts and the Possibility of Change,” p. 701. 41 One could argue that these interpretations are in fact misconstruals of Aristotle. In the following chapter, I will present Thomistic interpretations of form and matter that differ from Brower’s conceptions on several important points; in particular, I will argue that a form is not a property in any sense of the term.

Brower claims, Aristotelian endurantism is a three-dimensionalist analogue of perdurantism. Both theories attempt to preserve us from contradictory conclusions about persisting objects by positing non-persisting entities that bear contradictory properties directly. I will have more to say about the implications of this parallel below.

Perdurantism’s Implausible Conclusions Now that I have described the chief candidates for a theory of diachronic identity, it is time to identify the weaknesses of each candidate. What follows is not an exhaustive catalog of defects but merely a demonstration that each theory has at least one important flaw. In this overview I hope to show that some flaws are so deep that a viable theory must differ in some fundamental respects from the theories on offer today.

Because this work is an attempt to improve upon existing endurantist theories, I do not intend to offer a thoroughgoing refutation of perdurantism. Given that philosophers acknowledge endurantism as the more intuitive theory of diachronic identity, demonstrating that it can answer serious metaphysical challenges should suffice to secure endurantism’s status as the better of the options. Nonetheless, I will touch briefly on some of the shortcomings of perdurantism that other philosophers have yet to address. Because stage theory has gained ascendancy over worm theory following Sider’s defense of the stage theory view, I turn first to problems with this strand of perdurantism.

One striking problem for stage theory is that its semantics cannot provide a plausible interpretation of statements about development. Take for example the statement “Tom grew three inches last summer.” Stage theorists cannot offer an adequate explanation of the referent of the term ‘Tom.’

Initially, one might suspect that it would suffice to identify the present stage of the worm Tom as the referent. On this reading, the statement is true because Tom’s present stage (Tomp) has temporal counterparts (let these be Tomi to Tomn) that form a continuous series of stages ranging in height from his initial height h inches to h+3 inches. I do not dispute the adequacy of this interpretation as a truthmaker; that is, the existence of such a series of counterparts may account for the truth of the statement. However, the stage theoretic semantic interpretation is dubious here. That model claims that ‘Tom’ is referring to a particular stage, but this seems false. For we might make such a statement even if Tom were deceased, in which case we could not be referring to Tom’s present stage. Even in the case in which Tom is alive, it seems doubtful that “Tom grew three inches during the summer of

2005” should pick out just Tom’s stage that is simultaneous with my utterance. That is, this is not a statement about Tom’s present stage, even if one can explain the truth of the statement in terms of the properties of counterparts to Tom’s present stage. The state of affairs in virtue of which the statement is true does not involve Tom’s present stage; regardless of the time of utterance (after the summer of 2005, anyway), this statement will be true in virtue of the events of 2005. Nothing about

Tom’s present stage alters the truth of the statement. Furthermore, our ability to make such a claim about Tom truthfully even after his demise indicates that we are not talking about Tom’s present stage. In other words, the statement about the non-existent Tom shows that ‘Tom’ does not have some hidden indexical function such that it is shorthand for ‘Tom-here-and-now.’ Furthermore, although Tom’s present stage is not the stage to which we refer, no other stage is a superior candidate. For we can arbitrarily choose any of Tom’s stages, and it will have as counterparts that

74 series of stages that serves as the truthmaker for the statement in question. Consequently, the worm view is the only satisfactory four-dimensionalist view in this case. The statement is about Tom simpliciter, and, on a four-dimensionalist view, the entity most closely corresponding to Tom simpliciter is the worm Tom.

The failure of stage theory just described is a wide-ranging problem. Statements about development are common in talk of living things. Therefore, talk about growth, decline, metamorphosis, alteration, and like phenomena will defy cogent semantic interpretation in the stage theorist’s framework.

A deeper problem for perdurantism in general is that it rejects the possibility of numerical identity through change. That is, the perdurantist cannot say that a perduring object x at t is identical with object x at t' in light of some unchanging ontological feature or constituent. For the perdurantist, any object that persists does so by having temporal parts, which preclude the possibility of a changing object with an unchanging part. Rather, the perdurantist says that objects are merely

“genidentical” across time in light of satisfying some form of relation known as the genidentity relation. That is, objects that satisfy this relation just are the sort of objects to which we ascribe identity over time, even though they are not truly identical to one another. Importantly, perdurantists do not agree on precisely what this relation is or whether it is the same for all types of objects; well-known candidates include spatiotemporal continuity, psychological continuity, and biological continuity.

As Sider notes, if perdurantism is true, then genidentity is “as good as it gets,” for there are no parts or objects that are strictly identical across time, at least if all temporal parts are instantaneous.42 Now, if the four-dimensionalist ontology of perdurantism is correct, this is not a crushing objection.

However, the changeless persistence of some property or part, if possible, would be a superior candidate for “true persistence.” Accordingly, all else being equal, a theory of diachronic identity that allows for changeless persistence would be superior to four-dimensionalism. Over the course of the next two chapters, I will argue that an endurantist theory can do exactly this.

Another common objection to perdurantism is that it does not permit “real change.”43 In brief, the objection is that change requires something beyond the mere succession of qualitatively different parts. Objectors differ on the justification for this requirement, but temporal parts theorists respond to them more or less identically: change is nothing more than this succession of qualitatively different parts, and the consequences of this conclusion are acceptable.

Sider uses this perdurantist definition of change to deflect two longstanding criticisms from J.M.E.

McTaggart about the perdurantist approach to change. The first criticism from McTaggart targets the perdurantist’s understanding of time, which requires that all facts are ‘timelessly true,’ or true

42 Sider, “Four Dimensionalism,” p. 196. 43 See, for example, Peter Geach, Logic Matters (Oxford: Basil Blackwell, 1972), section 10.2; Peter Simons, Parts: A Study in Ontology (Oxford: Oxford University Press, 1987); Lawrence Lombard, “The Doctrine of Temporal Parts and the No- Change Objection,” Oderberg, “Temporal Parts and the Possibility of Change,” p. 707.

76 independent of what time the present happens to be. For instance, it is timelessly true that my sandwich that was cold last Thursday morning was cold at that time. The passage of time has no effect on the truth of this proposition. If facts are timelessly true, McTaggart claims, change does not occur, for change requires an alteration in the truth value of a proposition. Secondly, McTaggart argues, the perdurantist equates temporal change with differences in spatial properties, but this is absurd. Spatial differences in properties, such as a color gradient in a field of dirt, do not amount to change.

Sider’s response to these claims is succinct and representative of the perdurantist rejoinder to the

“no change” objection. According to Sider, the perdurantist accepts that change occurs without a change in the truth of propositions, and he likewise accepts the analogy between space and time. In support of the second point, we can (and sometimes do) say that change occurs in space, though the terminology of change is typically applied in a temporal context. For instance, we may say that a countryside changes from plains to desert, or that a road changes from flat to steep.44 Thus, the perdurantist happily accepts McTaggart’s characterizations of perdurantism, but as descriptions of a correct theory rather than as reductiones ad absurdum.

Regardless of the success of Sider’s reply, the “no change” objection has force, albeit in a limited context. However, the argument must proceed somewhat differently than it does in McTaggart’s formulation. Instead of attacking the perdurantist’s view of change in general, we must examine the

44 Sider, Four Dimensionalism, pp. 214-15.

77 perdurantist’s answer to the question: what changes? It then becomes clear that there is no appropriate candidate for the subject of change in the four-dimensionalist framework.

The argument takes the form of a dilemma: on the perdurantist view, either stages change or worms change. These are the two types of continuants in the four-dimensionalist view, so there are no other candidates for the subject of change. Stages, however, cannot change. A stage exists simply at one moment in time, and it does not possess complementary properties. Thus, we cannot speak of a succession of properties in the case of a stage. Furthermore, resorting to temporal counterpart theory is of no avail here. For the main reason to invoke temporal counterparts would be to suggest that a given stage that is F changes in light of having a counterpart that is non-F.45 In other words, the stage is F at t and non-F at t'. This approach, however, would treat a stage as a worm by claiming that the stage has temporal parts; that is, it has distinct parts located at different times that enable it (not merely a counterpart) to possess complementary properties. In addition, claiming that stages change would undercut one of the motivations for positing temporal parts, that is, denying that any object possesses complementary properties simpliciter.46

45 Sider hints at the possibility of this view but does not explicitly endorse it when explaining his temporal counterpart theory. He raises the objection that “Stages don’t continue” [italics in original]. It is unclear whether he believes that this objection is true but harmless or merely false. However, he does proceed to explain that stages can be said to have past or future properties in virtue of their counterparts’ possessing certain properties. From this one might conclude (wrongly) that temporal counterpart theory allows stages to change. 46 One might try to argue that stages change in light of having properties such as being F and being not-F in ten minutes. But these are not complementary properties, and trying to interpret them as such renders the perdurantist susceptible to the problem of temporary intrinsics once again.

Because stages cannot change, a four-dimensionalist is forced to argue that worms change. This claim, however, must be qualified. Worms do not possess their contingent properties simpliciter.

Furthermore, they possess these properties derivatively only in the sense that they are composed of temporal parts that possess contingent properties. Thus, worms can be said to change only in virtue of the succession of their temporal parts. One may ask, then, whether an object that does not possess a property simpliciter can truly be said to change. Mark Hinchliff illustrates the problem thus:

The perdurance theorist may seek to account for our intuition [about a bending candle] in terms of the candle's having [temporal] parts which have the [different] shapes, but alteration requires the candle to have the shapes not derivatively but directly. If the candle never has the shapes itself, it cannot change its shape [italics in original].47

The perdurantist here may wish to respond that alteration can happen in virtue of a difference in derivative properties. In other words, the perdurantist will claim that we should embrace his view of alteration so long as perdurantism is superior to endurantism in other respects. Even if one concedes this point to the perdurantist, Hinchliff’s objection retains a dialectical, if not conclusive, force. If it is possible to devise a consistent theory that explains change in terms of an object’s losing and gaining properties simpliciter, that theory will be superior to perdurantism in at least one respect.

Apart from the foregoing objections to four-dimensionalism, the great limitation of the theory is that it is counterintuitive and unnecessarily complicated. Many philosophers, including some

47 Mark Hinchliff, “The Puzzle of Change,” Philosophical Perspectives 10 (1996), pp. 120-21.

79 perdurantists, acknowledge the counterintuitiveness of the theory. They admit that we do not conceive of persisting objects as stretched out across time or composed of time-slices prior to philosophical reflection.48 Although some perdurantists protest to the contrary, 49 this partiality in favor of endurantism seems correct. In our pre-philosophical moments, we think of these objects as undivided unities across time—the analogy between spatial parts and temporal parts is not obvious to the layman. It is not intuitive to claim that I am a space-time worm who grows by having successively larger parts, or that I am a stage who grows (perhaps) by having successively larger counterparts. Perhaps—contrary to my arguments thus far—one of these theories is the best philosophical explanation of change and identity; if so, we will need to accept a profoundly revisionary metaphysics. Although this is not a conclusive objection to perdurantism, it is reason enough to look for a better version of endurantism, a theory that preserves and builds upon pre- philosophical intuition.

Endurantism’s Lack of Explanatory Power The chief shortcoming of contemporary endurantism is readily apparent: its lack of attention to the ontology of persistence. Most endurantists have focused on the semantics of their position without developing the ontology undergirding the theory. One finds endurantists such as David Oderberg saying about the phenomenon of change that “it is hard to know what else the person puzzled about the phenomenon of change is asking for, if not perhaps a semantic account of change that does not

48 See, for instance, Michael Rea, “Temporal Parts Unmotivated” The Philosophical Review 107.2 (1998) p. 225; and Yuri Balashov’s perdurantist account in “Enduring and Perduring Objects in Minkowski Space-Time,” Philosophical Studies 99.2 (2000), p. 130. 49 Sider remarks that “[T]he strangeness of speaking of [temporal parts and other philosophical concepts] is adequately explained by their exclusion from ordinary domains of quantification...In my experience, unprejudiced folks seem to find the idea of temporal parts a natural one.” Four-Dimensionalism, p. 218.

80 entail contradiction.”50 Rejecting any ontological criterion of identity, as Merricks does, further restricts endurantism to semantic pronouncements. When endurantists do on occasion turn to ontology, it is only to deal with some ramification of a semantic doctrine, not to provide an independently motivated metaphysics that makes endurantism intelligible. However, challenges from perdurantists, such as Sider’s request for a clear definition of whole presence, show that endurantists must expound and defend their theories in ontological terms.

Even in the absence of metaphysical objections from opponents, endurantism requires an ontological grounding. This requirement is unsurprising, for endurantism is an ontological rather than semantic theory. Its central claims are claims about the way that objects persist through change.

Although semantic explanations will remove some confusions about the theory, they alone cannot explicate endurantism. Instead, endurantism’s central ontological claims must either be brute facts, capable of elucidation but incapable of proof, or conclusions rooted in more fundamental ontological premises.

Endurantists tend to have treated their basic claims as brute facts, sometimes implicitly, sometimes explicitly. As the previous chapter showed, Merricks clearly rejects any deeper ontological grounding for at least one important aspect of endurantism, the criterion of identity. Other theorists are not as clear in their commitments. However, in practice they unite with Merricks in embracing the standard endurantist view that we can provide only dialectical justifications of endurantism. These

50 Oderberg, “Temporal Parts and the Possibility of Change,” p. 694.

81 justifications take three forms. First, we can demonstrate that four-dimensionalism is internally inconsistent or implausible so that we should embrace its rival. Second, for those already favorable to endurantism, we can argue that the theory is internally consistent and largely free of uncongenial implications. Finally, we can emphasize the solidarity of three-dimensionalism with pre- philosophical beliefs. However, there can be no explanation of endurantism in more fundamental ontological terms: the endurance of objects can be articulated and defended, but it cannot be explained.

Recognizing the incompleteness of this approach, Oderberg suggests that the endurantist ultimately must justify his or her account in metaphysical terms: “[A]ny semantic theory of change (like semantic accounts in general) has metaphysical implications, and so must be assessed in part on whether those implications are correct.”51 Nonetheless, he provides no such account.

To be successful, an endurantist theory must address several problems that endurantists have heretofore ignored. Most fundamentally, the theory must explicate whole presence—and thus identity through time— in ontic terms. As I suggested in the previous chapter, such an explication might proceed by defining whole presence in terms of the persistence of a bare particular or a nuclear bundle of tropes. Whatever the solution, it is essential that whole presence is explained in terms of strict identity across time; perdurantism gives up on explaining diachronic identity in terms of any permanent objects or parts, so it remains to endurantists to explain how strict identity over

51 Oderberg, “Temporal Parts and the Possibility of Change,” p. 694.

82 time is possible. This initial achievement will prepare the way for addressing in ontic terms the various problems that cluster around the issue of persistence through time: the Problem of Material

Constitution, the problem of temporary intrinsics, the Indiscernibility of Identicals, and difficulties related to self-change.

Accordingly, the subsequent chapters of this work will attend almost exclusively to metaphysical questions. A further step, which goes beyond the limits of this project, is to elaborate the semantic defense of endurantism that follows from its ontic foundations. Endurantists do need to reconcile everyday talk about change with their metaphysical claims, and they also must explain how to precisify such everyday talk. However, these explanations presuppose a metaphysical theory of diachronic identity. Until this theory is expounded, the turn to semantics is premature.

Apart from these general flaws pertaining to most endurantist theories, there are problems unique to specific theories. As I have already discussed in detail, Merricks’s theory eschews any criterion of identity. However, it is possible to identify such a criterion, specifically by explaining the diachronic identity of an object or substance in terms of the diachronic identity of one of its metaphysical constituents. Consequently, it is incumbent upon any theory of diachronic identity to do so, and

Merricks’s view fails in this respect.

Of the alternatives, relationalism is perhaps the most metaphysically revisionary, though it does not offer a metaphysics of endurance per se. The theory understands properties as relativized to times—

83 a notion that David Lewis dismisses outright. Construing properties as relativized to times has the consequence that nothing is ever simply F, but only F-at-t. This maneuver practically assimilates properties to relations. Indeed, van Inwagen avoids speaking of x’s being F in favor of x’s having F at t—this sounds like a description of a relation rather than a description of a property.52

Relationalism moreover implies that there are not actually incompatible properties, except those that would exist (per impossibile) at the same time. Both perdurantists and endurantists have found these consequences unappealing.53

Curiously, van Inwagen’s idiosyncratic approach to property possession enables him to skirt the more central ontological issues at stake in the endurantist/perdurantist debate. For instance, he states something that sounds like a doctrine of whole presence, namely that only Descartes simpliciter is present at each of the space-time regions of Descartes’ existence:

Now the region R [Descartes’ spacetime “career”] is the union of an infinite class of regions that includes R1 and R2 and indenumerably many other regions much like them. Each of these regions, I say, is occupied by, and only by, Descartes. It follows from this and our "plausible supposition" that it is Descartes that occupies R.54

However, van Inwagen provides no ontological explanation of what it is for only Descartes to occupy these regions; the reader infers merely that temporal parts of Descartes do not occupy the spacetime regions of his “career.” Van Inwagen does add that Descartes, construed as the sole occupant of an extended spacetime region, can be said to possess only those properties that he

52 “Four Dimensional Objects,” pp. 247, 250. 53 Lewis, On the Plurality of Worlds, pp. 52-54; Hinchliff, “The Puzzle of Change,” pp. 121-22. 54 “Four Dimensional Objects,” p. 251.

84 possesses at all subsections of that region; for instance, we can say that Descartes is French but not that he is a soldier. This claim gestures at some thought of an essence or “nucleus” of properties belonging to the extended Descartes, but there is no further investigation of this line of thought.

The problem for the adverbialist is similar to that just described for the relativist: there are some metaphysical claims, but these create problems as great as those they purport to solve. Moreover, none of these claims allows the endurantist to state how an individual is the same (we could say

“wholly present”) at different times without temporal parts. Adverbialism offers a counterintuitive theory of properties, on which adverbially modified properties are more basic than their unmodified counterparts. Here again, the order of analysis seems backward: we ought to say that properties in their ‘simpliciter’ form allow us to explain adverbially modified properties. The cost of this solution is so great that it is preferable to find an alternative. An added difficulty for adverbialism, mentioned by Oderberg, is temporal adverb dropping, or an inference from ‘x is tly F’ to ‘x is F.’ If permitted, this move reintroduces the appearance of contradiction and so undermines the attempt to dissolve the problem of temporary intrinsics.55 The adverbialist thus must stipulate—in another ad hoc maneuver—that this form of inference is illegitimate.

Regarding sententialism, I have no objections on metaphysical grounds. However, like other purely semantic theories, it is subject to the criticisms given above until it is coupled with an ontology.

55 Oderberg, “Temporal Parts and the Possibility of Change,” pp. 696-97.

Notably, Brower’s Aristotelian theory does offer an ontological grounding for endurantism.

Therefore, it appears to be the best candidate for an endurantist theory. However, it makes a substantial and regrettable concession to perdurantists that invalidates it as a candidate theory.

Brower grants to perdurantists that persisting entities do not possess their properties directly but instead derivatively. There are two unfortunate consequences of this line of thought. First, it abandons one of the distinctive, positive features of endurantism, namely direct property possession.

This feature is attractive not only because it differentiates endurantism—aside from Brower’s version—from perdurantism but also because direct property possession avoids an important problem raised by indirect property possession. The problem is that Brower’s accidental unities rely for their existence on more basic hylomorphic compounds: seated-Socrates exists—it seems almost too obvious to state—because Socrates is seated. Yet Brower wishes to tell the story in reverse so that Socrates is seated derivatively in virtue of being the same as seated-Socrates. This approach conflicts with the underlying metaphysics and should be rejected.

Furthermore, Brower’s theory does not benefit from indirect property possession as perdurantism does. This becomes clear when one examines how indirect property possession works on each view.

On the perdurantist view, stages possess properties directly, and worms possess them indirectly.

Accordingly, when one predicates incompatible properties of a persisting worm,56 one removes the apparent contradiction by noting that differing temporal parts possess the properties directly.

56 This explanation pertains only to the worm view of four-dimensionalism. The approach would differ for Sider’s stage view, which I explain in further detail below.

Embedded in this solution is an appeal to property possession by different (temporal) parts.

However, when one predicates incompatible properties of an Aristotelian compound, one does not resolve the contradiction by appeal to parts. Instead, one appeals to different wholes compounded out of constituents, such as seated-Socrates and standing-Socrates. Here, the basic hylomorphic compound is a part of these greater complexes. Brower himself notes this reversal of the part-whole relationship.57 Accordingly, it is not clear why property possession should be derivative rather than direct: why would the part not possess the property that pertains to the whole? There are indeed cases where a property predicated of a whole does not hold of a part (for instance, ‘quadruped’ predicated of a horse and, incorrectly, of its mane), but here we can predicate the same property of both the complex and the part. There does not appear to be any reason to claim that the hylomorphic compound possesses the property derivatively, other than attempting to solve the problem of temporary intrinsics. If Brower offered a principled reason for derivative property possession, his theory would be more persuasive, but he does not.

The metaphysical inversion at the center of Brower’s theory raises an important question: Is

Brower’s theory truly an endurantist theory? Although he styles his view “Aristotelian endurantism,”

Brower repeatedly notes its affinity with perdurantism.58 The most striking parallel between the theories is that accidental unities function much like temporal parts by directly—and temporarily— possessing incompatible properties. Only Brower’s claim that enduring objects are parts of accidental unities distinguishes his view from perdurantism. Furthermore, the claim that enduring

57 “Aristotelian Endurantism,” p. 898. 58 “Aristotelian Endurantism,” pp. 883, 891, 901.

87 objects are parts of greater wholes or complexes is also a departure from typical endurantist thought.

Consequently, while Brower is a self-styled endurantist, his theory does not appear to preserve any of the virtues of endurantism.

To sum up the foregoing comments on endurantist theories: a viable endurantist theory must provide an ontic explanation of substantial identity through time. Unfortunately, most current endurantist theories treat only semantic issues, or they broach metaphysical topics only to deflect a limited range of objections, not to provide an ontological foundation for endurantism.59 The one theory that offers more in the way of ontology, namely Brower’s, sacrifices some of endurantism’s strengths and creates several metaphysical difficulties in doing so.

Conclusion A satisfactory theory of diachronic identity is not to be found among the current versions of endurantism and perdurantism. As presented by its recent advocates, endurantism lacks the ontological foundations to explicate whole presence and to establish a criterion of identity through time. Perdurantism, in contrast, propounds a distinctive metaphysics that discards two desirable features of any theory of diachronic identity: strict identity through change and an enduring subject of change that directly possesses its properties.

59 I am not suggesting that any philosopher should in fact create an ontology merely to support endurantism. However, if endurantism seems to be a plausible theory on its own, one might wonder how some ontology, motivated independently of endurantism, could provide a foundation for endurantist claims.

To move beyond the shortcomings of current theories of identity through time, an endurantist theory with a deeper ontology is necessary. Such a theory will retain endurantism’s strengths—direct property possession and strict identity through change—while supplying its defects. Only once such a theory is developed can endurantism be judged on its ability to address contemporary puzzles about diachronic identity, such as the problem of temporary intrinsics and the Problem of Material

Constitution.

In the next chapter, I will propose that the metaphysics of Thomas Aquinas can furnish the ontology needed to construct a robust endurantism. Developing a Thomistic theory of diachronic identity will allow for a substantive explication of whole presence and, in turn, more rigorous solutions to problems about identity through time.

CHAPTER 3: DIACHRONIC IDENTITY IN THOMAS AQUINAS

A Different Theory It is clear that contemporary theories of diachronic identity are inadequate. There is a need for a new theory, and that theory must be endurantist. It also must provide a robust ontology so that whole presence is no longer merely a term of art but instead a claim about what is the same in an enduring individual. Finally, this theory should not be an ad hoc confection, but it should instead offer some arguments in its favor independent of the endurantist and perdurantist debate.

The chief claim of this dissertation is that the metaphysics of Thomas Aquinas offers such an ontology. Chapters 4 and 5 will show in what ways metaphysical claims taken from Thomas can solve the problems that plague today’s versions of endurantism. To prepare the reader for the arguments of those chapters, the present chapter reviews and interprets Thomas’s thoughts on diachronic identity. This preparatory work comprises three tasks: describing some of the fundamentals of Thomistic ontology, providing some motivation for these fundamental claims, and applying St. Thomas’s metaphysics to issues of diachronic identity when he has not explicitly done so himself.

This chapter will confront some difficulties that beset any study of Thomistic metaphysics. The first is that St. Thomas, who was by profession a theologian, never wrote a full-length systematic treatise on metaphysics (or on natural philosophy, which he would view as the subject matter of the present study). Rather, he addressed metaphysics and natural philosophy as he deemed appropriate throughout a variety of works: theological treatises, commentaries on the works of other writers

(chiefly Aristotle), a few opuscula, and polished write-ups of public debates (his quodlibetal and disputed questions). Consequently, it is usually necessary to examine multiple works to determine St.

Thomas’s views on any issue of ontology. An interpreter trying to reconstruct an underlying metaphysical theory cannot simply lift a seamless, comprehensive set of claims from a single

Thomistic source. The interpreter must instead piece together this theory from a variety of sources with different subject matter and purposes.

The need to consult multiple works leads to a second difficulty. Although St. Thomas’s life was comparatively short, he was an extraordinarily prolific writer. Accordingly, he had numerous occasions to develop or reverse his positions on philosophical issues. Commentators vary on the extent to which Thomas changed his mind on specific issues, but all agree that his later works differ from his earlier thought in at least some respects. It is therefore possible that there is no single theory of identity that Thomas embraces throughout his life; there may be theories differing from each other on important points that he held at various times.

The final and most formidable problem is that St. Thomas never formulated a theory of identity.

Rather, in the course of discussing theological topics such as the resurrection or transubstantiation, he presents metaphysical principles that inform theology. For instance, he argues that the relics of the saints are identical with parts of the saints’ living bodies (in a qualified sense) as a result of the identity of the bits of underlying matter.1 However, there is no Thomistic writing that explicates

1 ST III, q. 25, a. 6, ad 3.

91 what it is for bits of matter to be identical; Thomists must construct an explanation of this teaching from brief remarks in a variety of works. In this way, because he is never investigating identity per se, Thomas ignores certain questions that, though of secondary importance to a theologian, are of great interest to a philosopher.

As we will see, these difficulties have led commentators to arrive at very different conclusions about what St. Thomas said about identity over time. Furthermore, among those philosophers who find his remarks on identity incorrect or incomplete, there exist sharp differences about what St. Thomas should have said.

There is no definitive solution to these problems. One can hope to find that Thomas’s works are consistent in their claims about identity, but there is no a priori guarantee of consistency. Insofar as the claims of Thomas’s works conflict, the reader must judge which set of claims is superior on its own merits. When the problem is one of incompleteness rather than inconsistency, modern interpreters must either accept a fragmentary theory as-is or supplement it with their own views.

Although Thomists can present arguments in favor of adopting one set of Thomistic claims or extending Thomas’s thought in a particular direction, these arguments will be not come from St.

Thomas. His modern-day readers must devise them.

When explicating Thomistic principles concerning diachronic identity, I will draw primarily from one source, his Sentences Commentary.2 Thomas’s most extensive discussions of identity appear in this early writing, and many of his later writings repeat passages from the commentary almost verbatim. Therefore, the Commentary is a particularly good source for an extended, coherent discussion of identity that has numerous (partial) parallels in later works.

Drawing on the Sentences Commentary also presents one great disadvantage. Because it is an early work, the Sentences Commentary does not include some insights and clarifications that Thomas offers in his later writings. Similarly, the Sentences Commentary does not reflect Thomas’s mature ontology, which includes some refinements absent from his early writings. Fortunately, this problem is minimal (or so I hope to illustrate): Thomas’s comments on identity in both his early and later writings draw upon basic Aristotelian premises that he accepted throughout his career. Nonetheless,

I will at times draw upon works other than the Sentences Commentary to explain, reinforce, or extend remarks made in this early work. As I do not wish the reader to infer that Thomas would have agreed with all these explanations and supplementations at the time of writing the Sentences

Commentary, I will state explicitly when I am going beyond the Sentences Commentary. Furthermore, when the claims of a later work appear inconsistent with the Sentences Commentary, I will note these differences as well.

2 For discussions of his ontology in general I will rely on other, shorter works, such as the De principiis naturae.

As we shall see, Thomas’s writings do not include all the claims needed to formulate a theory of diachronic identity. Moreover, some of the claims explicitly formulated in his works are ambiguous and thus require considerable interpretation. Consequently, to articulate a complete theory of identity I must at times go beyond Thomas’s thought. In some cases I can simply argue that my interpretation of the text is the best reading of Thomas; in other cases, however, I will argue for claims that are Thomistic in character but found nowhere in St. Thomas. To avoid any confusion about what Thomas’s positions are, I will note whether a conclusion is explicitly in his works, possibly in his works, or entirely my own.

As stated previously, my goal is to formulate an endurantist theory that will succeed where contemporary theories have failed. Although defending some new claims is necessary for this task, I believe that Thomas’s metaphysics supplies the bulk of the necessary material. Accordingly, it is to his metaphysics I turn, beginning with the foundations of his ontology.

The Basics: Substance, Form, and Matter For Thomas, the world is a world of individuals, or, to be more precise and Aristotelian, individual substances. Individuals possess features and characteristics but are not possessed by or part of other entities. In this way they are foundational; they are the substrates for other entities, such as colors, shapes, and lengths. Furthermore, although individuals are metaphysically complex, they are not constituted by separate, independently existing entities. In other words, there are no Platonic universals in Thomas’s metaphysics. On his view, all individuals and their components are

94 particulars—non-repeatable entities—and universals exist in the mind as representations of many particular entities.3

Thomas provides his clearest description of the ontology of material beings in De principiis naturae, a short work dating to the period in which he composed the Sentences Commentary.4 In this treatise he identifies the basic metaphysical constituents of material substances. Additionally, he offers some arguments that these constituents are basic. This work is therefore a helpful starting point for understanding Thomas’s ontology and the motivation behind it.5

The work begins by making two distinctions that are related to change. According to the first distinction, existence is either potential or actual. A house, for instance, may be blue now, and thus actually blue; however, at the same time the house would be potentially white because it can become white. According to the second distinction, existence can be substantial or accidental. For a thing to exist substantially is for it to be an individual substance, such as a man. In contrast, the accidental existence of an individual applies to the different ways in which the individual substance may exist, the different features it may take on. For instance, a man may be white or non-white, tall or short.

3 See, e.g., SCG III, c. 75; Sentencia libri De anima II.12. Thomas also notes in these passages that a common or universal nature, such as humanity, is found in many individuals. Yet he further states that natures found in individuals are individual and numerically distinct from one another though specifically the same. Accordingly, they are “universals” in the sense that the same universal concept can be abstracted from each individual nature. 4 Jean-Pierre Torrell dates both the Commentary and De principiis naturae to 1252-1256. See his Saint Thomas Aquinas, vol. 1, The Person and His Work (Washington, D.C.: The Catholic University of America Press), pp. 332, 349. 5 Thomas defends his ontology of material beings elsewhere in more metaphysical terms, as opposed to the physical account given in De principiis naturae. For instance, he uses an argument from predication in his Commentary on the Metaphysics and an argument based on the limitation of form by matter to establish the form-matter distinction. For further details see John Wippel, The Metaphysical Thought of Thomas Aquinas (Washington, D.C.: Catholic University of America Press, 2000), pp. 302-305.

This latter sort of existence presupposes the former: an individual can assume different features only if it first exists as a foundation for those features, as a substance.6

These initial observations should be acceptable to almost anyone who endorses a substance-based metaphysics. Thomas’s first two distinctions simply mark out two types of entities: individual substances and features of substances, which he terms “accidents.” For Thomas, these are the basic types of material beings, and individual substances are the more fundamental of the two.7

With his next claim Thomas begins to introduce the structure of individual substances. He observes that “there is something in potency to each of the types of existence.”8 In the case of substantial existence, there is a foundational substrate or “prime matter” that is potentially an individual substance. In the case of accidental existence, there is a subject—an individual substance—capable of acquiring a different shape, color, or some other feature. In both instances, there is some metaphysical constituent, the part that is in potency, which serves as the basis for a more complex whole.

6 De principiis naturae c. 1. 7 Note that an individual substance, though a substrate for features or accidents, is not a “bare particular” for Thomas. As we shall discuss shortly, every individual substance is a substance of a certain sort with an essence. For instance, an individual human is not a featureless substrate with the feature “humanity” layered on top, but a substance that is constituted in part by its essence, humanity. Whether one wants to call the essence a feature is a terminological quibble; what is important is that the substance is not a mere substrate, indifferent to all further features. 8 De principiis naturae c. 1. “Ad utrumque esse est aliquid in potentia.”

Thomas then complements these remarks about potency with a discussion of actuality. Just as there are entities in potency to the two types of existence, there are entities that confer each kind of existence.9 Any entity that confers existence Thomas terms ‘form’; these are divided into substantial forms and accidental forms, depending on whether they confer substantial existence or accidental existence. By way of illustration, Thomas states that a man is the sort of substance that he is, namely a human being, in virtue of his substantial form (we shall also see shortly that it is important for this form to inhere in the right sort of matter). Similarly, that same man possesses certain features, such as whiteness, in virtue of accidental forms.10 For this remainder of this chapter, I will use the term

‘form’ to refer to substantial forms unless otherwise specified.

As Jeffrey Brower observes, form and matter are often “functional” concepts in Thomas’s thought.

In many contexts—but not all—the designations of form and matter indicate the role that one entity plays relative to another, rather than some absolute status.11 For instance, De principiis naturae states that a man may be the matter for an accidental form, such as whiteness. That man, however, is not matter to the exclusion of possessing any form (he is not prime matter). In fact, he can be considered as a composite with a formal component, namely a substantial form. In other instances, Thomas will talk about the human body or parts of the human body as the matter of a human being, even though the body possesses a number of accidental forms. This point will prove important when we discuss matter’s role in identity through time.

9 The term ‘entity’ here simply denotes a type of being. Thomas does not consider form and matter to be real, complete beings. 10 De principiis naturae c.1. 11 See Brower’s “Matter, Form, and Individuation,” in The Oxford Handbook of Aquinas, ed. Brian Davis and Eleonore Stump (New York: Oxford University Press, 2012), p. 88.

In this context it is also important to note that a substantial form, though determinative of a material individual’s kind, does not constitute everything that is essential to that individual. Because a material object always must have some matter, and that matter differs according to the individual’s kind, Thomas recognizes that kind-specific matter is also an essential part of each material substance. For instance, Thomas notes that all humans have a specific sort of flesh (soft tissue) and bones as their matter. This sort of kind-specific matter and the substantial form constitute the essence of a material individual.12

At the heart of Thomas’s ontology of material substances, then, are the following claims:

1. There are two basic types of material entities: individual substances and the features or

accidents of individual substances.

2. For each type of entity, it is necessary to posit principles that stand in potency to these

entities (prime matter for substances and substances for features).

3. For each potential principle, there is an actualizing principle: the substantial form for prime

matter and the feature or accident for individual substances.

12 See, for example, De ente et essentia c. 2.

The first claim is familiar and widely (though not universally) accepted among philosophers. There are many arguments for and against an ontology of substances and particular (non-repeatable) features—enough that I do not plan to add to them.13 The second claim, however, requires some further defense to satisfy those readers who are not already Aristotelians. It may be plain enough that there must be subjects that potentially possess certain features, but it is less clear that there must be prime matter in potency to being an individual substance. Therefore, it is important to explain

Thomas’s arguments for this thesis. In addition, some readers may not be convinced that substantial forms are necessary to account for the existence of different kinds of substances. This point, too, needs further explanation. It is not my goal here to convert non-Aristotelians; I hope merely to make Thomas’s positions more intelligible to those who are not already sympathetic to him.

Thomas’s writing in De principiis naturae indicates that his attempt to explain the phenomenon of change—specifically the destruction and emergence of substances—shapes his claims about prime matter and substantial forms. In fact, in the passage just after the lines discussed above, Thomas proceeds to discuss two types of generation and two types of corruption or destruction that correspond to substantial and accidental existence. These passages reiterate his claim that form is the source or principle (principium) of an entity’s actuality, while matter is the principle of potential

13 For a brief list of recent arguments in favor of Aristotelian substance theory, see Patrick Toner, “On Aristotelianism and Structures as Parts,” Ratio 26:2 (June 2013), pp. 148-49. Among the problems that he and others believe are solved by an Aristotelian substance ontology are the Vagueness Argument for Unrestricted Composition, the Overdetermination Argument for Eliminativism, the Problem of Material Constitution, the Problem of Temporary Intrinsics, the Problem of Constitution, the Problem of the One and the Many, and difficulties in explicating essentialism.

99 existence. However, precisely what roles these principles play in explaining change requires further elucidation.

Thomas discusses the generation of macroscopic objects—in particular humans—to illustrate his points. His examples are somewhat biologically inaccurate, however, so they need updating.

Unfortunately, updating them involves introducing a great deal of complexity, and this in turn limits their usefulness as examples. Therefore, I will turn to a simpler example of change, a chemical reaction, to present his theory.

The Haber process, the chemical reaction typically used to generate ammonia, involves the synthesis of one molecule of nitrogen and three molecules of hydrogen to yield two molecules of ammonia.

The process is represented in simplified form by the following equation:

N2 + 3 H2 → 2 NH3

Assuming that each of the reagents and the products is a substance,14 three hydrogen molecules and a nitrogen molecule are corrupted to generate two ammonia molecules. What, however, does it

14 The reader who does not consider these molecules to be substances is welcome to substitute another reaction for the Haber process. Nothing in my argument rests on the substantiality of these particular molecules, which were chosen for their simplicity.

100 mean to say that these substances are corrupted and generated? It is possible to suggest a few roughly sketched options:

1. The reagent molecules (the nitrogen and hydrogen compounds) simply vanish from

existence, and the product molecules emerge ex nihilo. There is nothing that persists

throughout the reaction.

2. The reagent molecules exchange and combine components to create the products. Only the

atoms persist through the reaction, so they are the subjects or substrates for the change.

3. The reagent molecules cease to exist, but a foundational component of these molecules, their

matter, endures the change and is organized into the configuration of the two product

molecules.

Neither of the first two options is acceptable to Thomas. The first option will be rejected by

Aristotelians (like Thomas) and non-Aristotelians alike. It is patently absurd: it explains nothing.

Thomas would reject the second option as a characterization of substantial change as well. For some event to be a change, Thomas holds, there must be something that undergoes or endures the change, a subject of the change. This enduring item exists before, during, and after the change and serves as the substrate for the entities that come into being and cease to be during the change. In the case of substantial change, the subject cannot be a substance, for substances are destroyed and generated in substantial change. Thus, there must be some other substrate that survives the change.

According to Thomas, although the atoms can be said to survive the reaction in a qualified sense,15

15 Thomas thinks that substantial parts are not numerically the same as those parts when extracted from their wholes. Instead, he holds that a substance, when incorporated into another substance, is no longer the same substantial individual that it was previously. Because this doctrine is not central to the present discussion, I will not examine it further. For the most relevant Thomistic text, see the opusculum De mixtione elementorum; Joseph Bobik’s discussion of

101

they cannot be its subjects if the change is substantial. For, if the atoms are substances, then substances endure the change, and the change is not substantial but merely a change in relations.

The same holds true if we assume that the atoms are parts of substances that endure the change as well; this reading simply construes substantial change as a change in the relations between substantial parts. Therefore, there must be some other subject that endures the change.

This line of reasoning that opposes the second solution directs us toward solution three. In the case of substantial change, some foundational substrate that is not a substance persists through the change. This substrate, prime matter, is the foundation both for the initial substances (the hydrogen and nitrogen molecules) and for the final substances (the ammonia molecules). Prior to the change, prime matter is united with the substantial forms of hydrogen and nitrogen to constitute hydrogen and nitrogen molecules, and afterward it is united with the form of ammonia to yield ammonia molecules.

Examining substantial change clarifies the basic role of prime matter: it is the underlying substrate for substantial change. When a process destroys one or more substances and yields a new substance or substances, prime matter persists through this change. This finding, however, provides little insight into the role of substantial form. Thomas tells us that form confers substantial existence upon an individual, but one may wonder whether this function is superfluous so long as a substance is defined by possessing certain properties. Why not say that the substantial existence of ammonia is

this writing in Aquinas on Matter and Form and the Elements (Notre Dame, Indiana: Notre Dame University Press, 1998) is particularly helpful.

102 a brute fact—ammonia simply is a substance that has certain properties, and there is no further need for explanation? Or, as an alternative, why not claim that ammonia’s substantial existence supervenes upon the relations between the nitrogen and hydrogen atoms?

Understanding why Thomas posits the existence of substantial forms requires understanding his view of the relationship between a substance and its characteristic functions or operations. The starting point for this understanding is an Aristotelian dictum accepted by Thomas: “Function follows being” (operatio sequitur esse).16 The claim captured in this dictum is that the functions or operations of a thing indicate the sort of existence that thing enjoys. In the case of a material substance, there is a function or functions not explained by the material constituents (the

“substantial parts”) themselves. Therefore, by the axiom above, the existence of the substance is more than a brute fact; we require some further explanation for this new activity. The axiom also requires that the explanation be ontic in nature: the additional function points to an additional esse.

Accordingly, the substance is an additional entity above its parts; it cannot be reduced to relations between the parts.

16 It is difficult to find an explicit defense of this dictum in Thomas. For one of the most relevant defenses, see ST I-II, q. 4, a. 5, arg. 2, Leon. 6.42. In this article Thomas considers whether the body is necessary for human happiness. The objector claims that the body is necessary because happiness is a perfect operation, which presupposes perfect being; but the soul lacks perfect being when separated from the body, so the soul cannot be happy without the body. For our purposes, the key claim is that perfect operation follows upon perfect being: “Sed operatio perfecta sequitur esse perfectum, quia nihil operatur nisi secundum quod est ens in actu.” In his reply to this objection, Thomas states that the soul has perfect being apart from the body and therefore enjoys a perfect operation. Here he basically paraphrases the claim from the objection that a perfect operation follows upon perfect being, so we can be confident that he accepts this dictum.

103

A more contemporary way of framing this explanation is to say that Thomas embraces a “top-down metaphysics” in which the functions of a substance are not merely explained by the collection and interaction of the functions of its components. Rather, the substance itself is responsible for certain of its operations, even though these operations may require the activity of the constituents. Given this unique set of functions explained by the substance itself, the axiom requires that the substance have some existence greater than the separate existences of its substantial parts.

Recognizing that substantial existence is not explained by the existence of any substantial parts,

Thomas nonetheless searches for an explanation in the metaphysical composition of the substance.

He does so because, as was noted earlier, Thomas holds that actuality, for instance exhibiting a certain feature or acting in a certain manner, demands an ontological explanation in a composite individual. Because a substance acts in a way that is not explained by its substantial parts, such as atoms or limbs, there must be some other ontological constituent accounting for this activity.

Thomas offers explanations of the causal primacy of this constituent, substantial form, in numerous works. Indeed, this claim is entrenched in his lifelong metaphysical thought, as it is part of his philosophical inheritance from Aristotle.17 We thus find Thomas in his Commentary on the

Metaphysics, a later work, explaining form as the principle that causes the components of a substantial whole to constitute a unity:

17 For some of Thomas’s early thoughts on this subject, see In I Sent., d. 17, q. 1, a. 2, ad 2. In this passage, however, he merely notes that (most) accidents of a substance are caused by the subject. Only in later texts does he specify that it is form, the active component of the subject, that causes a substance’s accidents.

104

[W]hen the things of which the composite is made up are separated from each other, “this”—the whole—does not remain after its dissolution. For when the elements have been actually separated, flesh does not remain; and when its letters have been separated, the syllable does not remain. But the elements, i.e., the letters, remain after the dissolution of the syllable, and fire and earth remain after the dissolution of flesh. Therefore the syllable is something over and above its elements, and it is not only its elements, which are vowels and consonants, but there is also something else by which a syllable is a syllable. And in a similar way flesh is not merely fire and earth, or the hot and the cold, by whose power the elements are mixed, but there is also something else by which flesh is flesh.18

In this passage Thomas argues that the mere existence of the constituents of a whole does not account for the existence of the whole. The evidence for this claim is the persistence of the constituents when the whole ceases to exist. If the constituents by themselves accounted for the existence of the whole they compose, the constituents would exist if and if only if the whole exists.

Because the parts outlast the whole, Thomas contends that another principle must account for the existence of the whole. That principle is form, here termed “something else by which x is x.” On

Thomas’s view, then, a substantial form is responsible for the ontological existence of an individual substance.

The passage just quoted merely suggests that a substantial form confers causal powers. In the Summa theologiae Thomas is more explicit about the causal efficacy of form:

Consider that the nobler a form is, the more it governs corporeal matter, the less it is immersed in matter, and the more its power or operation surpasses those of matter.

18 In Aristotelis libros Metaphysicorum lib. 7, l. 17, n. 1674, ed. Marietti 398.11. “[Q]uia dissolutis, idest divisis ab invicem his, ex quibus fit compositio, haec, scilicet totum non adhuc remanet post dissolutionem. Sicut iam divisis elementis non remanet caro, et divisis literis non remanet syllaba. Elementa vero, idest literae, remanent post dissolutionem syllabae. Et ignis et terra remanent post dissolutionem carnis. Igitur syllaba est aliquid praeter elementa; et non solum est elementa, quae sunt vocalis et consonans; sed alterum aliquid, per quod syllaba est syllaba. Et sic similiter et caro non solum est ignis et terra, aut calidum et frigidum, per quorum virtutem elementa commiscentur, sed etiam est aliquid alterum per quod caro est caro.”

105

Accordingly, we find that the form of a mixed body has another operation not caused by its elemental qualities. And, as we proceed from less noble forms to nobler ones, the more we find that the power of the form surpasses elemental matter.19

According to Thomas, a mixed body—a material substance composed of more basic parts—has operations or characteristic functions that are not explained by the qualities or activities of those basic parts or “elements.”20 Instead, these operations are attributable to the complex substance itself, or, more precisely, to the form by which it is a substance. Thomas does not argue for this point but states it as an observation: we see that complex substances possess causal powers that are not explicable in terms of their constituents’ causal powers. For him, then, this claim is evident.

For us, however, such a claim may not be so evident. Indeed, in metaphysics and the philosophy of science the reducibility of systems-level powers to the powers of constituents is a topic of ongoing debate. It is not my intention here to settle this debate, but it will be helpful to offer some motivation for Thomas’s view. In a thoughtful discussion of Thomas’s top-down metaphysics,

Eleonore Stump provides just this sort of motivation. Drawing on the example of a water molecule, she notes that the molecule possesses causal powers distinct from the individual or combined powers of its constituents. Specifically, the molecule is capable of forming hydrogen bonds in a manner that its constituent hydrogen and oxygen atoms cannot when existing outside the molecule.

19 ST I, q. 76, a.1, co., Leonine edition, volume 5, 210. “Sed considerandum est quod, quanto forma est nobilior, tanto magis dominatur materiae corporali, et minus ei immergitur, et magis sua operatione vel virtute excedit eam. Unde videmus quod forma mixti corporis habet aliquam operationem quae non causatur ex qualitatibus elementaribus. Et quanto magis proceditur in nobilitate formarum, tanto magis invenitur virtus formae materiam elementarem excedere.” Thomas’s works are cited hereafter in the following form: [edition], [vol.].[page]:[line]. 20 A complication that I pass over here is that the elemental parts of a substance are not truly parts on Thomas’s view. He holds that the simple, elemental substances that enter into the composition of a complex substance—air, earth, fire, and water—do not remain as substances or parts in the complex substance. Rather, they remain only by virtue of their power (virtute). See De mixtione elementorum, Leon. 43.155-56:123-53.

106

Stump remarks that this power emerges only when the atoms are configured as parts of a water molecule; it is not merely the summed effect of the powers of these atoms. That is, the hydrogen atoms and oxygen atoms, considered as a mere collection—not as a unified molecule—do not have a collective ability to form hydrogen bonds. In contrast, they do have certain collective properties that are the same whether they are compounded in a water molecule or not, such as a certain total mass.21

If we grant Thomas’s top-down metaphysics—even if only for the sake of argument—we may nonetheless wonder what a substantial form is. This is difficult to pin down, for Thomas quite frequently tells us what it is not. He states that it is not an “accident,” that is, it is not any sort of being that depends upon the substance for its existence, such as whiteness of the eyes or being someone’s brother.22 From this one can deduce that a substantial form is not a feature or a relation, but it is unclear how one ought to categorize substantial form.

It is worth mentioning that there is nonetheless a temptation to consider substantial form a property or relation because it plays some of the roles reserved for relations or properties in contemporary metaphysics. Unfortunately, some contemporary Thomists and Aristotelians gravitate toward discussing form in these terms. Jeffrey Brower, for example, refers to form as a “complex organizational property.”23 For Thomas this characterization strays from the truth because it

21 Eleonore Stump, “Emergence, Causal Power, and Aristotelianism in Metaphysics,” in Power and Capacities in Philosophy: The New Aristotelianism, ed. John Greco and Ruth Groff (New York: Routledge, 2013), p. 58. 22 De principiis naturae c.1. 23 “Aristotelian Endurantism,” p. 894.

107 suggests that a substance’s form is a dependent feature of that substance, much like skin color or shape. But substantial form makes the individual substance what it is, so it is fundamental and essential in a way that properties are not. Similarly, Eleonore Stump terms substantial form a

“configuration or organization of the matter of [an] object” that confers species-specific causal powers. Although Stump’s reference to species-specific causal powers is accurate, the description of form as a configuration deviates from Thomas’s thought. For the term ‘configuration’ suggests a relation, and a relation is yet another type of accident. Stump appears to admit as much and to have chosen the phrase ‘configuration or organization’ faute de mieux.24 These examples demonstrate how difficult it can be to translate the concept of form into readily understandable language that is not simply a slight revision of Thomas’s original phrasing.

To explain substantial form more fully, it is helpful to note that Thomas thinks of it as an ‘essential principle’ of substance. Thomas explicates form’s nature as an essential principle by stating that it makes an individual what it is and confers substantial existence on it. As Thomas puts it, a form is that by which an individual is what it is. An ontologically minimalist reading of Thomas might conclude that a substantial form is not really something other than the thing itself—the form is simply the thing understood in terms of its membership within a natural kind. The tendency to consider form a mere conceptualization of the substance is further reinforced by Thomas’s denial

24 See Stump’s “Non-Cartesian Substance Dualism and Materialism without Reduction,” Faith and Philosophy 12 (October 1995), p. 524n10: “I am not convinced that my phrase “configurational state” is the only or even the best way of conveying the meaning of the Latin ‘forma.’” In her later Aquinas she uses the term ‘configurer’ for form but retains ‘configuration’ as well.

108 that a form is a substance or an accident. Because substances and accidents are the only types of beings he acknowledges, it would seem that form can be nothing other than the subject.

Yet Thomas does conclude that a substantial form is ontologically distinct from the substance of which it is the form. He refers to the form as a ‘formal part’ of the substance. For instance, in the early work De ente et essentia Thomas writes, “But the word which signifies that from which the nature of the species is taken, and signifies it as excluding designated matter, signifies a formal part.”25 Here

Thomas is explaining that the term for the principle that accounts for species membership, such as

‘humanity,’ indicates a formal part of the whole individual. Therefore, although a substantial form is not something superadded to an existing individual—it is not an accident—it also is not coextensive with the individual. The form is a part.

With this sketch of form and matter complete, it is now possible to restate Thomas’s basic ontology of physical things more clearly. All material things are individual substances or features or relations of these substances. Any material entity is composed of an actualizing component and an actualized component, or form and matter. In the case of individual substances, the actual component is its substantial form, which determines kind membership and bestows species-specific causal powers.

The potential component is prime matter, which serves as a foundation for the form and persists through change. Together, these components constitute the core of the individual substance.

25 De ente et essentia c. 2, Leon. 43.370:281-283. “[N]omen autem significans id, unde sumitur natura speciei cum precisione materie designate, significat partem formalem.”

109

More Thomistic Metaphysics: Esse, Accidents, and Properties Although we have now reviewed the concepts that are foundational in Thomas’s treatment of identity, it is necessary to discuss his metaphysics somewhat further before presenting his views on that topic. His treatment of other aspects of ontology—particularly existence and the possession of features—casts further light on precisely what he believes about the roles of form and matter in identity.

Thomas is noteworthy is holding that there is a real distinction between an individual’s essence

(what it is) and its existence (esse). He takes the latter to mean the act of existing, or the principle that confers existence upon a thing, not merely the fact that the individual exists.26

Because my argument does not rest on the acceptance of esse as a distinct metaphysical principle, I will not examine Thomas’s reasons for positing esse at length. His arguments for a principle that accounts for an individual’s existence are typically situated within demonstrations that this existential principle is distinct from the individual taken as a whole or from that individual’s essence. In these contexts, Thomas points out that the act of existing does not contain in itself any features that allow for differentiation between species or individuals: on its own, existing is an act common to all beings. He thus takes esse to be distinct from the principle by which kinds are different (essence, or

26 Thomas presents esse understood as the ontological constituent that accounts for the fact of existing in numerous texts, including SCG I, c. 22: “Omnis res est per hoc quod habet esse.” For a fuller list of texts, see Wippel, The Metaphysical Thought of Thomas Aquinas, p. 407.

110 more precisely, form) and the principle that distinguishes individuals of the same kind (matter).27

Consequently, although every individual substance has an act of existence, esse is not an element of the individual’s essence or principle of individuation.28

More important than Thomas’s argument for the essence/esse distinction are his presuppositions about the character of esse, namely:

1. Esse is a principle of each existing individual.

2. On its own, esse does not distinguish individuals or species from one another.

3. Esse is not an essential part (an element of a being’s essence).

Each of these deserves some further explanation. About the first point Thomas remarks that ontological constituents are made distinct within a given kind (or “multiplied”) by being “received in” or limited by another ontological principle. This is to say that one instance of an ontological constituent can be individualized, or made distinct from similar instances of its type, only through being united with (“received by”) another type of ontological constituent. In the case of material beings, our concern here, distinction or limitation occurs as the result of being received by different

27 See, e.g., De ente et essentia. c. 5. 28 Note, however, that some commentators argue that esse is the principle of individuation in Thomas’s metaphysics. See Joseph Owens, “Thomas Aquinas (b. ca. 1225; d. 1274),” in Individuation in Scholasticism: The Later Middle Ages and the Counter Reformation, edited by J.J.E. Gracia (Albany, NY: SUNY Press, 1994), p. 175.

111 substantial forms and matter. When compounded with these distinguishing constituents, esse is distinct from one individual to the next.29

That esse does not individuate (account for the distinction between individuals) is clear from

Thomas’s earlier writings, such as the De ente et essentia. There Thomas writes that existence is distinct from essence in all beings other than God, both immaterial and material. He notes further that the distinction of individuals in one kind is impossible for immaterial beings but possible for material ones. In neither case does esse effect the distinction of kinds or individuals.30

Finally, esse is not the same as a thing’s essence, or its matter and form. Matter and form account for what a thing is, but esse does not. This is one of Thomas’s most distinctive metaphysical claims, and it does not require further exegesis here. What is important for our purposes is that Thomas does not consider esse to be part of the essence of material substances, even though these substances require esse to exist.

After esse, there are still other elements of Thomas’s ontology that are relevant to an analysis of diachronic identity. These remaining ontological elements fall under the heading “accidents.” For

Thomas this group comprises the nine Aristotelian ontological categories other than substance: quantity, quality, action, passion, place, position, time, relation, and habit. The first seven of these

29 See, e.g., De ente et essentia, c. 4; SCG II, c. 52. 30 De ente et essentia, c. 5.

112 categories occupy much the same role as monadic properties in contemporary metaphysics: they are the features of individuals. Of the last two, “relation” corresponds roughly to relations as understood by today’s philosophers,31 and “habit” refers to the state of having or possessing certain items, such as clothing, armor, or tools.32

Although several categories of accidents resemble monadic properties, Thomas makes a distinction regarding these categories that contemporary philosophy does not make regarding properties.

Specifically, he distinguishes accidents that a substance may or may not possess from features that it always must possess in virtue of its kind membership and features that it necessarily possesses as a result of individual essential principles. In the first group he would place features such as the whiteness of Socrates’ skin (Socrates can easily become reddish with sunburn), and in the second

Thomas includes features such as Socrates’ capacity for humor, a capacity that he has simply in virtue of being a human.33 While accidents of the first type are simply called ‘accidents,’ Thomas calls the second type ‘proper accidents’ or ‘properties’ (propria). He further distinguishes from these two

31 Medieval philosophers, however, rejected the claim that relations are polyadic properties. For discussion see Brower, “Medieval Theories of Relations,” Stanford Encyclopedia of Philosophy (2013), http://plato.stanford.edu/entries/relations- medieval/#3. It is also important to note that medieval philosophers differ from one another (and from contemporary interpreters of Aristotle) on the number of Aristotelian categories that are ontologically distinct. Thomas recognized the ten listed here. 32 For a discussion of Thomas’s derivation of the categories, see Wippel, “Thomas Aquinas’s Derivation of the Aristotelian Categories (Predicaments),” Journal of the History of Philosophy 25:1 (1987), pp. 18-22. 33 De principiis naturae, c. 2. Socrates would possess this capacity in the relevant sense even if he were constitutionally incapable of humor as a result of neurological damage. In other words, the capacity in question is the capacity for humor when functioning normally, not the capacity for enjoying humor right now. Thus, the capacity does not follow upon being a neurologically healthy human; instead, it results from being a human simpliciter.

113 groups a third category of accidents that belong necessarily to certain individuals qua individual but not in virtue of their kind membership.34

This distinction has important implications. Specifically, Thomas clearly separates necessary properties or propria from essence. The human essence, for instance, consists of a certain substantial form (a soul) and prime matter subject to that form. Neither of these essential constituents includes certain necessary properties that characterize all humans, such as risibility. To be sure, Thomas claims that the capacity for humor necessarily results from the human essence so that no human can be found without this capacity, at least in a very attenuated (and perhaps latent) form. However, neither property belongs to the essence per se. Accordingly, when discussing what necessarily characterizes an individual, it is critical to distinguish between essential constituents and the necessary properties derived from them.

The significance of accidents in general appears most clearly in the discussion of Leibniz’s Law, or the Indiscernibility of Identicals. Recall that the law states that two individuals are numerically the same only if they share all the same properties. In Thomistic terminology, the law requires that numerically identical substances must have numerically the same accidents. In the diachronic case,

34 Thomas mentions in particular that masculinity and femininity are such accidents. Quaestiones disputatae De anima q. 12, ad 7. See especially “…tria sunt genera accidentium: quaedam enim causantur ex principiis speciei, et dicuntur propria sicut risibile homini; quaedam vero causantur ex principiis individui. Et hoc dicitur quia, vel habent causam permanentem in subiecto, et haec sunt accidentia inseparabilia, sicut masculinum et femininum et alia huiusmodi; quaedam vero habent causam non permanentem in subiecto, et haec sunt accidentia separabilia, ut sedere et ambulare.”

114 then, a substance must retain all its accidents (and acquire no new accidents) to remain the same. As we shall see shortly, Thomas considers and rejects a proposition very similar to Leibniz’s Law.

Thomas on Identity At last it is possible to turn to Thomas’s thought on identity through time. As I have mentioned previously, Thomas never collected his thoughts on identity in a single work. However, his discussions of identity in his Sentences Commentary are so extensive that on their own they practically furnish enough material for an opusculum. Furthermore, his later writing on identity reiterates earlier points so consistently that it is quite straightforward to distill the key elements of Thomas’ thoughts.

Thomas as a Proto-Endurantist When speaking of a Thomistic theory of diachronic identity, I mean primarily a theory of what— ontologically—provides a foundation for sameness through time. This theory addresses the question, “What element(s) of an individual must remain the same for that individual to persist through change?” Examples of answers to this query include “all its parts,” “some essential element or substrate,” and “the individual’s mental or psychological states.”

This sort of theory does not directly address the question of concern to endurantists and perdurantists, namely, “How should we understand the relation between individual a at time t and the same individual at time t'?” As noted in a previous chapter, the perdurantist tells us that we should conceive of this relation as one between temporal parts of a whole, while the endurantist

115 eschews the notion of a relation between parts of the same individual at different times. Thomas’

“theory,” as I call his collection of views, does not speak to this second question.

Nonetheless, Thomas’ writings do offer evidence that he was an endurantist, or rather that it is not inappropriate to assimilate his views to endurantism. In several texts Thomas distinguishes between two classes of entities on the basis of their identity conditions. One class he frequently terms

‘permanent things’ or ‘persisting things’ (permanentes), and the other he calls ‘successive things.’ In the course of exploring temporal speech about God in the Sentences Commentary, he describes the two classes thus:

For there are certain things whose being is in becoming, and the perfection of these things does not exist except at the time when it reaches an end. Their perfection is better signified by the past tense; such are motions and successive things of that sort. Other things are such that their being consists in persisting, and their perfection is better signified by the present tense.35

In this passage Thomas makes an important distinction about the ways the two classes attain completion or perfection. Motions and other “successive things” exist incompletely, in a state of becoming, until their final moments. Therefore, they are signified in their perfected states by the past tense; for instance, ‘thrown,’ ‘caught,’ ‘burned,’ ‘traveled.’ The point is that these successive entities unfold over time, and only when we can say that they have ceased to exist can we also say that they have existed perfectly. Other entities, in contrast, are said to persist and to possess perfection that is

35 In I Sent., d. 8, q. 2, a. 3, ad 4, ed. Mandonnet 1.208. “[Q]uaedam enim sunt quorum esse est in fieri, et horum perfectio non est nisi quando venitur ad terminum, et horum perfectio magis significatur per praeteritum, sicut sunt motus, et hujusmodi successiva. Quaedam autem sunt quorum esse consistit in permanendo; et horum perfectio designatur magis per praesens quam per praeteritum.”

116 best captured by present tense predications. This is a limited and rather cryptic description of the second class of entities, but it appears to be a negation of the first class’s mode of existence. If this is so, then the second class does not have a successive mode of existence but instead a mode of existence that is not distributed across different moments of time. The use of the present tense to describe perfections of the second class indicates that members of the second class exist completely at each moment of their existence. This language seems to foreshadow the language of “whole presence,” but Thomas’s remarks are so brief that they suggest this parallel without confirming it.

Thomas elaborates on the nature of successive entities in the same book of the Sentences

Commentary. The context for this explanation is a defense of the infinity of God’s power. In this defense Thomas confronts an apparent dilemma about God’s instantaneous exercise of his infinite power: either he exhausts his power in this exercise, in which case his power is not infinite; or he can exercise his power further, in which case his action was not truly infinite. Thomas finds a third option that exposes the dilemma as false. It is logically impossible for the effects of God’s infinite power to exist simultaneously because the production of these effects requires motion, which is successive. It is Thomas’s description of this successive nature that is relevant for our purpose:

A power never produces an effect in a manner inconsistent with that effect’s nature. Accordingly, the motive power does not make all parts of a motion exist simultaneously; for then it would not be a motion, which is by nature successive.36

36 In I Sent., d. 43, q. 1, a. 1, ad 5, ed. Mandonnet 1.1004. “[N]ullus effectus producitur per aliquam potentiam per modum qui est contra rationem ipsius, sicut potentia motiva non facit omnes partes motus esse simul: jam enim non esset motus, cum de ratione motus sit successio.”

117

This text offers a negative definition of what it is to be a successive thing. A motion, by virtue of being successive, cannot have all its parts exist at once. If having simultaneously existing parts is incompatible with succession, one may conclude that succession implies having parts at a series of times. Thomas, of course, does not use the term ‘temporal parts’ in describing the parts of a motion, but it seems that he must have something of this sort in mind; in the case of motions, there are no spatial parts of which to speak. This is strong evidence that successive entities have temporal parts if they have any parts at all. Thomas does not tell us anything about persisting objects in this text, but it seems probable that they, in virtue of not being successive, can have all their parts at once.

Another Sentences Commentary passage offers some additional information about persisting things.

In this passage, Thomas considers whether the “now” or present moment of eternity is identical with eternity itself. He affirms that the two are identical, and in the course of his explanation his compares and contrasts the “now” and eternity on the one hand with various types of acts and their subjects on the other hand. Thomas’s remarks on acts measured by time and their subjects add further insight into the successive/persisting distinction:

For an act that is measured by time differs in being from that of which it is the act because movable things are not motions. They differ also by the nature of succession, for movable things are not successive things but persisting things.37

Here Thomas contrasts a motion and the thing moved by the motion as successive and permanent entities. Now the subjects of motions are substances, so one can infer that “persisting things” are

37 In I Sent., d. 19, q. 2, a. 2, co., ed. Mandonnet 1.471. “Actus autem ille qui mensuratur tempore, differt ab eo cujus est actus, et secundum rem, quia mobile non est motus; et secundum rationem successionis, quia mobile non habet substantiam de numero successivorum sed permanentium.”

118 substances. In conjunction with the previous passage, this text shows that substances are not successive things but instead entities that enjoy complete existence at any given moment. This text moves one step closer to aligning Thomas with endurantism.

This series of passages falls short of proving that Thomas was a conscious endurantist avant la lettre.

Nowhere does Thomas say outright that persisting entities cannot have temporal parts at different times. However, his texts defend positions that are congenial to endurantism and hard to reconcile with perdurantism. He differentiates the existence of substances from the existence of actions and motions by suggesting that the former type of existence enjoys completeness at any given instant in a way that the latter type does not. He also implicitly supports the claim that persisting entities do not have parts at different times. These two positions are similar to the acceptance of whole presence and the rejection of temporal parts, though they fall short of truly anticipating those contemporary positions.

The interpretations of two modern-day commentators, Lawrence Dewan and Joseph Owens, lend further support to the claim that Thomas’s views are congenial to endurantism. In an exchange with

Owens, Dewan takes up the question of whether there is temporal succession in the existence (esse) of material substances. Answering in the negative, he points to Thomas’s distinction between successive things, such as movements, and things whose intelligible character (ratio) does not include succession. Dewan notes that the latter category includes corruptible substances, which are subject

119 to change but are not changes themselves.38 For Dewan, the import of this contrast is that existence in general has an “all at once” character that distinguishes it from movement, which is successive.39

For our purposes, it is most significant that he recognizes in Thomas the distinction successive things and non-successive things such as substances.

Owens remarks on this same distinction, but he contends that for Thomas substances are successive in one respect and not successive in another. One the one hand, there is an unchanging essential foundation that ensures substantial identity. This is not successive or divided into temporal parts.

On the other hand, Owens claims that the existence (esse) of material substancs is a continuum with successive parts. He contrasts the two views of material substance thus:

Essentially the material substance, whether man, tree, iron or gold, remains unehanged in itself through all its variation in predicamental accidents and in temporal existence. It is the same person who is conceived, is born, grows, matures, loves, suffers, lives out his years and dies. There is no substantial change in the person. But the parts of his or her existence keep receding into nonexistence as the “now” pursues its relentless course.40

On Owens’s reading, Thomas treats the esse of also material beings, substantial or not, as “divisible in the fashion of a continuum.” Owens explains, “The existence itself takes place in an

38 Lawrence Dewan, “St. Thomas, Joseph Owens, and Existence,” The New Scholasticism 56 (1982), 417-18. 39 “St. Thomas, Joseph Owens, and Existence,” 420. 40 Joseph Owens, “Material Substance—Temporal or Eviternal?” The New Scholasticism 56 (1982), 445. On the essentially “unchanging” nature of substances, the following quote from p. 451, footnote 12, is also relevant: “The individual is fully human in each of the successive stages—embryo, fetus, child, adult—through which he exists in turn. The reason is that the essential perfection, which specifies the existence as human, remains unchanged. There is no increase in essential nature through prolongation in time.”

120 instantaneous and indivisible ‘now’ that keeps passing through the successive parts.” The persistence of esse, then, sounds rather like a temporal part theory that applies in part to material substances.

It is possible to see the interpretations from Dewan and Owens as rival characterizations of

Thomas’s anticipation of endurantism. The two commentators agree that the “stability” of essence underwrites the numerical identity of material substances. They disagree, however, on whether esse itself has a similarly non-successive character. Owens’s view, namely that a substance be essentially non-successive but existentially successive, deserves further investigation; it is a departure from the view that entities are either successive or non-successive, and it suggests an amalgam of the two modes of existence in material substances. That investigation lies beyond this scope of this work.

For the present, it is enough to note that in Thomas’s mind the successive/non-successive distinction serves to separate susbtances from non-substantial entities, at least in some respects.

The Principles of Identity The best starting point for Thomas’s theory of diachronic identity is his view of synchronic identity.

In one of his most extensive texts on identity, In IV Sent., d. 44, q. 1, a. 1, Thomas indicates that sameness of essence, or form and matter, is required for synchronic identity. Specifically, in the second objection of quaestiuncula 2, the objector remarks that Socrates and Plato differ by having numerically different essences or “forms of the whole.” The reply to this objection makes clear that

Thomas accepts this claim, and he in fact specifies that the essence or form of the whole should be identified with the composite of substantial form and matter. Therefore, we can conclude that

121 having the same form and the same matter is at least necessary for synchronic identity. We will return to this text later; meanwhile, let us consider some other passages.

In De principiis naturae, Thomas’s writing suggests that substantial form and matter may determine synchronic numeric identity. There he states:

Whenever things are numerically the same, as with Tully and Cicero, the form and matter are one in number. When things are the same in species but different in number, as with Socrates and Plato, the form and matter are not the same in number but only in species.41

In this passage Thomas tells us that form and matter agree or differ insofar as their subjects are the same or different. He then describes two scenarios in which this claim applies; however, he leaves the reader to determine precisely how to apply the claim. The first scenario concerns the same individual, Marcus Tullius Cicero, under different descriptions. Because in this case Cicero and Tully are numerically the same, there will be numerically the same matter and form regardless of how

Cicero is named. In the second, case, the individuals—Socrates and Plato—are not the same numerically though they are both of the human species. Therefore, their principles are not the same numerically, though each will have a human substantial form and matter suited to this type of form.

From this line of reasoning we know that any numerical difference in substantial form or matter will indicate a difference in the identity of the individual. Nonetheless, a critical question remains: Do the substantial form and matter actually account for the identity of the individual?

41 De principiis naturae c. 6, Leon. 43.47:63-67. “Eorum igitur que sunt idem numero, forma et materia sunt idem numero, ut Tullii et Ciceronis. Eorum autem que sunt idem in specie diversa numero, etiam materia et forma non est eadem numero, sed specie, sicut Sortis [Socratis] et Platonis.”

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To answer this question, we must turn to another passage that discusses synchronic identity,

Compendium theologiae chapter 154. In this text, Thomas compares the requirements for the resurrection with conditions of synchronic identity. It is critical for understanding Thomas’s views on synchronic identity and its relation to diachronic identity. He writes as follows:

In Socrates, then, or in Plato, there are this particular matter and this particular form. Accordingly, just as man is defined as being composed of matter and form, so if Socrates were to be defined, his definition would be that he is composed of this flesh and these bones and this soul. Therefore, because humanity is not some form in addition to soul and body but is rather a composite of the two, it is clear that when the same body is restored and the same soul survives, the humanity will be numerically the same.42

In this passage Thomas notes that individual material substances are necessarily composed of particular matter and a particular substantial form. He explains this necessity through a counterfactual: if material substances, such as Plato and Socrates, could be defined, their definitions would mention their particular bodies and souls. In other words, an individual must have this matter and this form; if those components are disunited at time t, the individual does not exist at t.

Furthermore, it is clear that sameness of matter and substantial form is sufficient for synchronic numerical identity, as Thomas says these components are “definitive” of Socrates, or necessary and

42 Compendium theologiae c. 154, Leon. 42.141:78-88. “In Sorte [Socrate] vero aut Platone includitur haec materia et hec forma, ut sicut est ratio hominis ex hoc quod componitur ex anima et corpore, ita si Sortes [Socrates] definiretur, ratio eius esset quod esset compositus ex hiis carnibus et hiis ossibus et hac anima. Cum igitur humanitas non sit aliqua alia forma preter animam et corpus, sed sit aliquid compositum ex utroque, manifestum est quod eodem corpore reparato, et eadem anima manente, eadem numero humanitas erit.”

123 sufficient for his identity. Thus, Thomas defends the following conditions for substantial synchronic identity:

Individuals x and y are numerically the same at time t if and only if they have numerically the

same matter and substantial form.

This view on the role of matter and substantial form in synchronic identity is also foundational for

Thomas’s position on diachronic identity. To be sure, Thomas never explicitly says that the conditions for diachronic identity are the same as those for synchronic identity. However, in the

Compendium theologiae text he does indicate his support for this view when explaining the conditions required for numerical identity before and after bodily resurrection. By establishing the sameness of form and matter as a condition for the resurrection, Thomas is implying that the conditions for synchronic identity are the same as the conditions for diachronic identity. Consequently, it is not merely the case that substance x must have this matter and this substantial form at time t. Just as being individual x at t requires having a certain substantial form and certain matter, so too being x at t and at t' means having numerically the same form and matter at t and t'. Because Thomas uses an observation about synchronic identity to justify a conclusion about diachronic identity, one can infer that he believes that the necessary and sufficient conditions for both phenomena are the same.

It is noteworthy that the passages above do not mention the features of a substance—its accidents—in explicating synchronic and diachronic identity. Thomas’s statements in a later work,

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Quodlibet 11, indicate why Thomas omits any discussion of accidents.43 This quodlibetal text addresses objections to the doctrine of the resurrection, the topic that most often occasions

Thomas’ discussion of identity through time. In question 6 of the text, Thomas inquires whether the human body that rises is numerically the same as the body of the deceased. He proposes an objection to pre-mortem and post-resurrection identity that hinges on the importance of accidents:

It seems that it is not the case [that the body rises numerically the same], for in the Topics the philosopher says that something is called “the same” if it is the same with respect to its proper accidents, accidents, and definition. But in the resurrection the body does not have the same proper accidents, for it now is inclined to laughter, but then it will not be. Nor does it have the same accidents, for now it is white, curly-haired, black, and so on, but then it will not be any of these things. Nor does it even have the same definition, for now it is defined as being mortal, but then it will not be mortal. Therefore, it seems that [the body] does not rise numerically the same.44

Thomas counters that this objection rests on a false reading of Aristotle’s text:

A thing is not called “the same in number” because it has the same accident and the same proper accident at this time and also at a later one. Instead, a thing is numerically the same because it is the same thing [simply] that possesses the accident or the proper accident. For instance, this is the case when a subject is the very same thing that had the accident, the proper accident, and the definition—not [only] those things that have the same accident, the same proper accident, and one definition.45

43 Torrell remarks that this quodlibet is typically dated to Thomas’s first period of teaching in Paris in 1256-1259, but some scholars have placed it as late as 1268 (Saint Thomas Aquinas, pp. 61, 211). 44 Quaestiones de quolibet 11, q. 6, arg. 1. “Et ostendebatur quod non. Quia, secundum philosophum in Top., illud dicitur idem numero quod est idem proprio, accidente, et definitione. Sed corpus in resurrectione non habebit eadem propria, quia modo risibile, tunc non; non eadem accidentia, quia nunc albus, crispus, niger, et huiusmodi, quae tunc non erunt; non eamdem etiam definitionem, quia modo definitur per mortale, tunc vero non mortale erit. Ergo videtur quod non resurget idem numero.” 45 Quaestiones de quolibet XI, q. 6, ad. 1. “Non enim dicitur idem numero illud quod habet idem accidens nunc et postea, et idem proprium; sed illud est idem numero quod est idem cum accidente et idem cum proprio, sicut cum subiectum est idem cum accidente, proprio, et definitione; et non illa quae habent idem accidens, idem proprium, et unam definitionem.”

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Identity over time does not require sameness of every feature. Instead, it is necessary only that the subject itself is the same substance that possessed those features. This passage rejects one of the centerpieces of later theories of identity over time, namely the diachronic version of Leibniz’s Law.

Thomas denies that an individual must possess numerically the same features over a period of time to be numerically the same individual for that time. He is able to do this because he views diachronic identity as identity of matter and form alone. This sets Thomas at odds with many of today’s metaphysicians, endurantists and perdurantists alike. As we will see in chapter 4, such a heterodox view (from a contemporary perspective) will allow Thomas some freedom from constraints under which today’s philosophers labor.46

The passages quoted above offer a general outline of Thomas’ views on diachronic identity. A substance at time t is identical with a substance at time t' if the substantial form of the “first” substance is numerically the same as the substantial form of the “second” substance and the matter is also the same. Accidental features do not play a role in diachronic identity (with one important exception to be mentioned below). Further explanation of these points requires us to turn back to the early Sentences Commentary, where Thomas’ most extensive treatment of identity is found.

46 One may wonder whether Thomas is stating here that a substance’s definition does not remain the same. If he means that, it would be quite problematic because the definition of a species is determined by its substantial form and matter. However, if we look at Thomas’s reply beyond the excerpt quoted above, he shows that he regards the sameness of definition differently from the sameness of features. The definition of man proposed by the objector was “mortal [rational animal]”, which seems to be false after the resurrection. Thomas replies that human nature remains intrinsically mortal, even if the effect of this mortality is blocked after the resurrection: “De definitione vero dicendum, quod licet resurgat immortale, tamen vera mortalitas non tolletur ab eo, quia natura humana erit ibi, quae ex se habet quod sit mortalis.” So it appears that the definition of the substance does remain the same, unlike the accidents and proper accidents.

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How Form and Matter Are Principles of Identity The discussion of identity in the Sentences Commentary occurs in two very extended passages. The first, In II Sent., d. 30, q. 2, a. 1, inquires whether ingested food and drink truly become part of the human being. The second, In IV Sent., d. 44, q. 1, aa.1-2, asks two questions: whether the human soul reunites with numerically the same body in the resurrection, and whether all the members of the human body will rise. This text is more foundational than the first in that it outlines the conditions for diachronic identity. The passage from the second book of the Commentary complements the exposition in the fourth book by addressing certain problem cases surrounding identity through change. Therefore, I will begin with a discussion of the passage in Book IV and then proceed to the Book II excerpt. While treating both passages I will note where later works reiterate or supplement the texts of the Commentary.

Sentences IV d. 44, q.1, a. 1, asks whether there is true identity of the individual before and after the resurrection. It is in the context of the resurrection that Thomas most often discusses identity, and parallel discussions can be found in questions about the resurrection in later works.47 It may seem inappropriate to draw conclusions about a philosophical theory of identity from this theological material; moreover, to readers acquainted with Thomas’ thought on human ontology it may seem illegitimate to make inferences about natural substances generally from statements about humans, for Thomas holds that humans are unique among material beings in that they have an immaterial component, namely the human soul. Using passages about the resurrection to state the conditions

47 See also Compendium theologiae c. 154; Quodlibet 11, q. 6; and SCG IV, cc. 80-81.

127 for diachronic identity of natural substances would thus seem to be the application of theological claims to an overly broad class of entities.

Although these concerns are reasonable at first glance, reading Thomas’s text shows that they are unfounded. If we consider the concern about applying theology to a philosophical problem, it is true that the resurrection introduces problems about identity that would not arise in a purely philosophical context. However, as we will see below, Thomas’ solutions to these theological problems always return to metaphysical rather than theological principles. To be sure, he believes that the resurrection is possible only through divine intervention. Yet the conditions for diachronic identity before and after the resurrection are metaphysical conditions, given in philosophical terms, even though God is the only agent who can act so that these conditions are satisfied.

It is also true that resurrection is possible only for humans on Thomas’ view. Nonetheless, the conditions for identity through an event such as the resurrection are the same for all natural substances. Thus, in the Summa contra Gentiles Thomas entertains the view that the resurrection is impossible because nothing can remain numerically identical if one of its essential principles is varied. He responds that it is correct that any substance’s essential principles must not vary if substantial numerical identity is to be preserved. However, the attempted application of this premise to the case of the human resurrection is mistaken: the substantial form, or soul, and human matter do in fact survive death.48 Thus, the same requirements for diachronic identity apply to all material

48 SCG IV, cc. 80-81.

128 substances. It simply happens that these requirements can be satisfied after death or disintegration only in the case of humans.

In the same Sentences IV passage Thomas explains two doctrines that are central to his theory of identity: 1) for material objects, identity through time requires the identity of the objects’ essential principles, namely form and (in a certain sense) matter; and 2) it is possible for an organism to have the same matter despite gaining and losing particles and bodily parts.

For our purposes, it makes sense to start in medias res, specifically at objection 4 of quaestiuncula 1.

This objection claims that the form of a “mixed body”—the form that organizes the simple material elements in a complex material entity—cannot be the same before and after the resurrection.

Consequently, this objection holds, the risen individual is not the same as the pre-mortem individual.

Two central premises in this argument are that 1) numerical identity requires identity of essential parts, and 2) the form of the mixed body is an essential part. The objector articulates the first claim as follows: “It is impossible for something to be numerically the same if its essential parts are numerically distinct.”49 Notably, in his reply to this objection, Thomas does not repudiate this claim.

In fact, he implicitly accepts it by instead arguing against the second claim. He tells us that the form of the mixed body is an accidental form, not a substantial form. The human body has just one substantial form, which is the rational soul. Changes in an accidental form do not create numerical diversity, so the corruption or alteration of the form of the mixed body has no bearing on

49 “Praeterea, impossibile est esse idem numero cujus partes essentiales sunt aliae numero.”

129 diachronic identity. Although the destruction of the soul would be an obstacle to numerical identity, the soul survives death. This rejoinder indicates that Thomas views substantial form as one of the essential parts on which the identity of the individual rests.

One might wonder what it means for a substantial form to remain numerically the same over time.

Thomas never elaborates on this point, but there is reason to believe that the identity of form is basic for him. In other words, the identity of a substantial form cannot be further analyzed. This fact results from the simplicity of substantial forms, which do not have further metaphysical constituents, though they may have a variety of powers. About two types of substantial forms, angels and souls, Thomas writes the following:

Thus, an angel or a soul can be called a quiddity or a nature or a simple form insofar as the quiddity of these things is not composed of different things. However, composition does occur in them, namely composition of quiddity and esse.50

Thomas states here that angels and souls are simple apart from being composed of what they are and that by which they exist (esse). Because esse is not determinative of identity, we can infer that simple forms such as souls and angels derive their identity simply from what they are. This, in turn, amounts to saying that the identity of substantial forms is not explained through anything else; it is a brute fact.

50 In I Sent., d. 8, q. 5, a. 2, co., ed. Mandonnet 1.230. “Unde Angelus vel anima potest dici quidditas vel natura vel forma simplex, inquantum eorum quidditas non componitur ex diversis; tamen advenit sibi compositio horum duorum, scilicet quidditatis et esse.”

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In d. 44, q. 1, a. 1, Thomas indicates that matter is another essential principle, but he does not elaborate further on matter’s role. In quaestiuncula 1 of a. 1, however, Thomas presents an objection to numerical identity before and after the resurrection that explains what is meant by ‘matter’ in this context. The objection is predicated on the diversity of matter existing in the pre-mortem and resurrected bodies. The objector remarks that upon decomposition a body is resolved into its elements or most basic constituents. However, these elements share nothing with the preexisting body except prime matter, which is common to all substances, including elements that were not parts of the pre-mortem body. Therefore, the body that is reconstituted from these elements will not be the same as the pre-mortem body. In reply, Thomas accepts the premise that mere sameness of prime matter is insufficient for identity of matter before and after the resurrection. He adds, however, that the matter of the elements that result from bodily decomposition shares dimensions with the preexisting body. The resurrected body then “inherits” these dimensions from the elements. Throughout the process of decomposition and resurrection, these dimensions underwrite an “identity of matter” that is more than sameness of prime matter. This reply indicates that

Thomas’s views on diachronic identity require a substance’s matter to remain the same in some manner that goes beyond mere sameness of prime matter.

Thomas further explicates the identity of matter in a later text, Quodlibet 11. There he reiterates his teaching that sameness of matter is needed for numerical unity. He also clarifies that he is not speaking of prime matter but of matter subject to dimensions. The latter sort of matter, unlike prime matter, is not pure potentiality devoid of characteristics. Instead, this matter is characterized by dimensionality that gives it length, breadth, mass, and the other quantifiable dimensions of a physical

131 object. In this same passage, Thomas also refers to matter understood this way as “body” (corpus).51

This sort of matter is the basis of numerical unity.52 In other words, only (prime) matter that is further subjected to dimensions (and thus no longer prime) has an identity of its own that serves as a foundation for the identity of the individual.

Another text from the Sentences Commentary, In II Sent., d. 30, q. 2, a. 1, further explains the relationship between the identity of matter and the identity of form. In this text Thomas considers whether ingested food and drink become the “truth of human nature” (veritas humane naturae), or material integral to the composition of the human body. One of the great difficulties in this question is what role matter plays in constituting true human nature because human matter seems to be in flux; there is constant gain and loss of parts. The objector couches this objection in the following terms: If matter underlies identity, then complete variation in matter leads to difference in individual identity. But anything that is consumed eventually is expelled, so food that is consumed cannot form part of the “permanent” matter that is the putative basis for individual identity.53 In addressing this problem, Thomas stipulates a further condition for the identity of matter. He states,

For we see that if fire is kindled and wood is added continually as other wood is consumed, the form of fire remains in the wood all the time; but whatever matter is consumed, still other matter follows it in which the species of fire is preserved. In this way that which pertains to the species and form of flesh will always remain

51 Quodlibet 11, a. 6, co. 52 Quodlibet 11, a. 6, ad 2. “Ad secundum dicendum, quod licet eadem materia faciat idem numero, non tamen materia nuda, nec quae facit principium in numero; sed una materia secundum quod est sub dimensionibus terminantibus ipsam, facit idem numero.” 53 In II Sent., d. 30, q. 2, a. 1, arg. 4.

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however much that [matter] that receives the form is continually consumed and replenished.54

Thomas expands on this requirement in his response to the fourth objection. This response is occasioned by the objection that matter derived from nutriment is always transient and therefore cannot underlie the identity of a persisting being. Thomas counters that any newly ingested matter becomes one with the preexisting matter, with the proviso that there must be some preexisting matter that remains so that identity may be preserved. He states:

Because the matter that is derived from nutriment is thoroughly combined with the matter that was there already [in the substance] and one whole is formed from the two, there is always a proportional destruction of both the nutriment and the preexisting matter [of the substance]. Accordingly, proportional amounts of both ingested matter and matter preexisting [in the substance] remain. In this way it never happens that everything that preexisted [in the substance] departs so that nothing remains of the preexisting matter, but there is always at least something. Further, whatever enters [the substance] becomes one with what preexisted, and so there is one matter and one individual throughout all life. 55

In other words, Thomas endorses the following requirement for the identity of matter:

54 In II Sent., d. 30, q. 2, a. 1, co., ed. Mandonnet 2.784. “Videmus enim quod si ignis accendatur, et continue ligna addantur, secundum quod alia consumuntur, forma ignis semper manebit in lignis; sed tamen materia quaelibet consumitur, alia materia sibi succedente, in qua species ignis salvabitur: et secundum hoc, etiam illud quod pertinet ad speciem et formam carnis semper manebit; quamvis illud quod recipit hanc formam, continue consumatur et restauretur.” 55 In II Sent., d. 30 q. 2, a. 1, ad 4, ed. Mandonnet 2.786. “[Q]uod cum illud quod advenit ex alimento aggeneratum, sit permixtum ei quod prius erat, et similiter unum effectum ex ambobus sit, semper fit deperditio in utroque proportionaliter; unde oportet quod et de utroque remaneat proportionaliter; et ideo nunquam contingit quod totum illud quod prius erat, abscedat, ita quod nihil prioris materiae remaneat; sed semper manet aliquid; et illud quod advenit, est unum cum eo quod praeerat, effectum; et ideo est materia una et individuum unum per totam vitam.”

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If a substance’s matter remains numerically the same over a span of time S, then for any

instant t in S, the matter subject to dimensions that composes the substance must include

some matter (subject to dimensions) that existed as part of the substance before t.

This response to the fourth objection also suggests that the continuity or identity of matter depends on the continuity of form.56 In other words, it appears that an individual’s substantial form unites ingested matter with the matter of the body to create one continuous matter under a single form.

However, if form makes all “bits of matter” into one collection of matter, it appears that form alone could be determinative of an individual’s identity. For form simply needs some matter to inform, not these particular bits of matter. The sameness of matter is irrelevant. If this is so, it seems that any individual will remain numerically the same so long as he has the same substantial form and some matter that is informed by that form. The “identity” of the matter itself appears useless because that identity comes from the form.

It is possible to respond on Thomas’s behalf by recalling that in his metaphysics diachronic identity mirrors synchronic identity. Just as being the same individual as a at time t requires having the same matter and form as a at t, so too being identical at t' to an individual a existing at t requires having the same matter and form as a had at t. In other words, numerical sameness of matter and form are requirements for both synchronic and diachronic identity. These requirements hold regardless of whether or not the activity of an individual’s substantial form accounts for the individual’s matter

56 Similar discussions appear in ST I, q. 119, a. 1, and Quodlibet 8, q. 3.

134 being the same over time. Thus, the identity of matter is a distinct requirement for diachronic identity even if the identity of substantial form ensures that matter remains the same through time.

A related and more difficult challenge to Thomas’s claims about the identity of matter turns on the very notion of having numerically the same matter. One plausible pre-philosophical view is that having numerically the same matter means having at least some of the same individual material parts or particles, perhaps even having the same material constituents particle for particle. On this view, an organism that has replaced all its matter (e.g., all its cells) over some period of time would no longer have numerically the same matter that it had at the outset of that period. Thomas acknowledges that many living substances, including humans, replace most if not all of their material particles over time,57 so his metaphysics is seemingly vulnerable to the objection that it does not offer a prima facie convincing view of the identity of matter.

Thomas confronts this objection directly in Book II of the Sentences Commentary. Here he comments on his functional understanding of the concept of matter, or the idea that “matter” does not simply pick out fundamental physical particles, but any entity that stands in potency to some form. Thomas thus notes that human flesh, considered as the matter of the soul, can itself be considered either formally or materially:

According to [Averroes’ view, which Thomas has accepted], there are not two types of flesh called “flesh according to matter” and “flesh according to species.” Rather, numerically the same flesh is called “flesh according to species” insofar as it partakes

57 Today’s biology has established that some cells, such as neurons, typically last for an organism’s entire life. Therefore, there is never wholesale replacement of matter at the cellular level in the case of humans.

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of the form and proper accidents attendant upon the species and “flesh according to matter” insofar as it consists of matter.58

By this distinction Thomas seems to mean that we can mean by “flesh” either a) the arrangement of a physical body (i.e., the structure of organs, muscles, and other tissue) that is specific to an organism or b) the actual components (individual cells, molecules, or atoms) that are subject to this arrangement at any given time. The former would be flesh according to species; the latter would be flesh according to matter. In explanation of this point, Thomas states that physical parts considered as matter and parts considered formally (“according to the species”) are the same material objects considered in different ways.

The distinction between physical parts considered materially and those same parts considered formally allows Thomas to claim in a nuanced fashion that matter can remain the same despite the loss and gain of physical parts. When he denies that the parts remain the same considered materially, he rules out identity of matter at the particulate (cellular, atomic, or molecular) level. Instead, he appears to be claiming that macroscopic components remain the same. In the same article from the

Sentences Commentary, Thomas explicitly states that parts according to matter do not remain constant, but parts according to form do:

The third view comes from Averroes in his Commentary on the first book of On Generation and Corruption. He says that no designated matter that is fixed and unchanging can be received in a body, but anything in the body can be considered in two ways: first, with

58 In II Sent., d. 30, q. 2, a. 1, ad 2, ed. Mandonnet 2.785. “[S]ecundum tertiam opinionem non est diversa caro secundum materiam distincta, quae dicitur caro secundum materiam, et caro secundum speciem; sed eadem secundum numerum caro dicitur secundum speciem, inquantum participat formam et proprietates consequentes speciem; sed secundum materiam dicitur, inquantum ex materia consistit.”

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respect to matter, and thus it is not permanent; second, on the part of form and species, and thus it is permanent.59

Using this approach, Thomas can argue that substances remain the same materially because certain macroscopic parts remain the same, even when particulate matter is changing constantly. He uses the example of fire mentioned above as an illustration: if a fire persists by consuming old wood and being replenished continually with new wood, the wood changes but the form of fire remains.

Similarly, in the body, the form of flesh remains even as the underlying matter changes.

This strategy creates a new problem in resolving the original concern. Now the cogency of Thomas’s theory rests on the criteria for the identity of parts considered according to species. There seem to be a few ways in which the criteria could be understood:

1. Identity at the particulate level, so that the part must preserve the same cellular, molecular, or

atomic constituents.

2. Identity at the structural level, so that the part must retain the same essential structures,

much as the substance must preserve the same essential parts.

3. Identity at the functional level, so that the part must continue performing the same function

(e.g., pumping blood throughout the body) even though the structures within that part may

change over time.

59 In II Sent., d. 30, q. 2, a. 1, co., ed. Mandonnet 2.784. “Tertia positio est quam ponit Averroes in 1 de Generat., dicens, quod nihil materiae potest accipi in corpore signatum, quod sit fixum et permanens; sed totum quidquid est in corpore, potest dupliciter considerari: vel ex parte materiae, et sic non est permanens; vel ex parte formae et speciei, et sic est permanens.”

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Unfortunately, Thomas does not explicitly discuss—much less endorse—any of these options. The selection of an explanation must be independent of his text.

The first option can be ruled out immediately. It would return us to the scenario in which particle- for-particle identity is required, and Thomas has dismissed that potential criterion already. The second option therefore seems more reasonable because it apparently does not entail identity at the particulate level. Yet this approach does not offer an ultimate resolution; the definition of the identity of matter simply devolves to the level of parts of parts. For instance, if one claims that numerically the same body must have numerically the same heart, then one must ask what makes the heart numerically the same. Because sameness of substantial form alone is not sufficient, the explanation must make reference to the material parts of the heart. Similarly, the numerical sameness of those parts will depend on the sameness of their own parts. Without an obvious means of stopping an infinite regress (to parts of parts of parts, and so on), this option is unsatisfactory.

Dismissing the first two alternatives leaves the third option, the requirement that certain parts of the body function continuously in certain roles, even if the constituents of these parts change constantly.

In a human, for instance, there is always some structure that functions to circulate the blood, even if the cells (and proteins, molecules, atoms, and so on) do not remain numerically the same. This functional view of the organs is consistent with texts in which Thomas characterizes organs as

138 instruments that enable the human substantial form or soul to exercise its different powers. Here is one such text from the Sentences Commentary:

The soul, despite being a simple form, is complex in its potency, so that diverse powers arise from its essence. Therefore, the body must have distinct parts proportioned to itself so that it can receive diverse powers. For this very reason the soul is said to be the act of a body with organs.60

This text shows that Thomas considers the organs as the physical outlets for the manifold powers of the soul. Because the soul has capacities to exercise numerous functions, the body must be differentiated appropriately to support each of these functions. In light of his functional view of organs, Thomas could claim that an organ persists so long as some part of the body continues to support the power of the soul corresponding to that organ. This position, however, is not explicit in his writing.

It deserves mention that this functional view of the identity of matter amounts to little more (but still something more) than another description of the identity of substantial form. It is form, not matter, that Thomas recognizes as the source of a substance’s characteristic functions. Accordingly, the persistence of these functions is guaranteed so long as the substantial form has some matter to inform. Nonetheless, matter does make a contribution. The preservation of characteristic functions requires the continuous presence of some particulate matter that supports those functions. Given that substances can lose matter, this continuous presence requires the sort of material overlap we

60 In I Sent., d. 8, q. 5, a. 3, ad 2, ed. Mandonnet 1.234. “Anima autem quamvis sit forma simplex, est tamen multiplex in virtute, secundum quod ex ejus essentia oriuntur diversae potentiae; et ideo oportet corpus proportionatum sibi habere partes distinctas ad recipiendum diversas potentias; unde etiam anima dicitur esse actus corporis organici.”

139 discussed above: even as some particles supporting a particular function are lost, some other particles supporting that function remain, and (sooner or later) new particles may be added. There is thus a functional-level analogue of the substance-level requirement for temporal overlap of a substance’s material particles.

We can now restate what Thomas probably means by identity of matter. He appears to hold that the numerical identity of matter is the preservation of essential physical parts, not in terms of their individual constituents, but in terms of their uninterrupted function. Nonetheless, there must be some continuity of the particles of matter; a substance cannot lose and replace all its material particles at once and remain numerically the same. This view of the identity—or rather continuity— of matter informs our view of the identity of substances: an individual substance would not remain numerically the same if it changed from having one type of organic structure or body plan to another, but it can survive the continual loss and gain of material constituents.

We are now in a position to summarize Thomas’s views on the identity or continuity of matter. He considers the matter of an individual substance at t to be identical to the matter of a substance at a later time t' iff the following conditions are satisfied:

1. The substance at t' has numerically the same substantial form as the substance at t.

2. The substance at t' has physical parts performing the same essential functions as the physical

parts of the substance at t.

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3. At the instant after t, t+1, the physical parts of the substance existing at t must each have at

least one physically quantifiable constituent that was also a constituent at t. This rule holds

for each subsequent instant ti of a substance’s existence, so that kind-specific parts existing at

any time ti between t and t' must have at least one physically quantifiable constituent that was

also a constituent at ti-1.

From this it is clear that Thomas does not believe that identity of matter is particle-for-particle identity. Instead, there is uninterrupted historical continuity of matter throughout a substance’s existence. In other words, at any given moment the substance must have some particulate matter, or matter under quantitative dimensions, that existed in the substance at the instant immediately prior.

An instantaneous wholesale replacement of matter would violate this principle. Furthermore, the substance must preserve the same core physical structures throughout its existence. Precisely what these structures are will vary from one sort of substance to the next, but Thomas indicates that

(macroscopic) organisms must retain the same organs throughout their lives.61

To sum up, Thomas requires the numerical identity of matter and substantial form for the diachronic identity of the substance. The diachronic identity of features or accidents is not required for the diachronic identity of substances. While the identity of matter is complex, depending on the continuity of particulate constituents within the major parts of a substance, the identity of form is a brute fact.

61 In chapter 5 I will discuss how this principle could be modified to allow for identity through fetal development and organ transplant.

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Rival Interpretations of Thomas There are two principal alternatives to my interpretation. The more common of these rival views holds that form alone is the principle of identity. On this view, matter plays no role in determining identity over time, so being the same individual amounts to having numerically the same form. The less common view is that esse is (or should be) Thomas’s principle of identity.

The primary shortcoming of both views is their inconsistency with Thomas’ writing. However, if either view were in fact an accurate interpretation of Thomas, it would lead to incoherence within

Thomas’ ontology. In the remainder of this chapter, I explain precisely why Thomists should reject both of these interpretations.

Substantial Form as the Sole Principle of Identity Several Thomists have claimed that substantial form is the principle of diachronic identity. That is, they claim that being the same individual throughout time requires nothing more than having the same substantial form. For sake of convenience, I will call these philosophers “form theorists.”

Some form theorists base their claims about diachronic identity on Thomas’s writings about the resurrection.62 This is unsurprising: Thomas makes most of his comments about diachronic identity

62 See, for example, Eleonore Stump, “Resurrection, Reassembly, and Reconstitution: Aquinas on the Soul,” in Die menschliche Seele: Brauchen wir den Dualismus? Ed. Niederbacher and Runggaldier (London: Ontos Verlag, 2006), pp. 151- 72; Christopher Brown, Aquinas and the Ship of Theseus (London: Continuum, 2005), pp. 118-24.

142 in this context, and the present work relies heavily on the same writings. However, form theorists are often concerned with a topic other than the basis of diachronic identity per se; they are concerned with the question whether a human person continues to exist as numerically the same individual after death. Views on this question fall into roughly two camps: the “survivalist” position, which maintains that the person persists as numerically the same individual after death; and the

“corruptionist” view, which rejects post-mortem persistence. Because Thomas holds that an individual’s soul persists after death but the body (matter) does not, the possibility arises that the post-mortem soul is not a human individual. This problem is relevant to the broader inquiry about diachronic identity, for the survivalist view entails that substantial form is the principle of diachronic identity. Although I will not evaluate the survivalist and corruptionist positions explicitly, I will mention that the view I am defending seems incompatible with any survivalist view.

The soteriologically focused approach of the form theorists is particularly evident in the writings of perhaps the most prominent form theorist, Eleonore Stump. In an article on the identity of humans before and after death, she neatly summarizes the chief argument for the form theorist’s position while discussing the identity of Socrates before and after his death:

[...] since what makes Socrates this individual substance is the individual substantial form which configures him, and since the substantial form can exist independently of the body, then for Aquinas the existence of the substantial form is sufficient for the existence of the human being whose substantial form it is.63

63 Stump, “Resurrection, Reassembly, and Reconstitution,” p. 166.

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The reasoning in this passage relies on three premises. First, Stump posits that substantial forms individuate, that is, they make substances to be the individuals that they are. She then asserts that the human substantial form can exist independently of the body. She finally assumes—but does not state—that the principle of individuation also functions as the principle of diachronic identity. From these three claims she concludes that the persistence of the human substantial form (the soul) ensures the numerical sameness of the individual even in the absence of the body.64

In both this work and her later Aquinas, Stump contends that her view follows from a claim that she attributes to Thomas, namely that constitution is not identity. In this particular case, the constitution of the substance by substantial form (the soul) and matter does not mean that that a substance is identical to form and matter individually or collectively. Stump expresses the view thus:

A human person is not identical to his soul; rather, a human person is identical to a particular in the species rational animal. A particular of that sort is normally, naturally constituted of an array of bodily parts and is composed of form and matter. Because constitution is not identity for Aquinas, however, a particular can exist with less than the normal, natural complement of constituents. It can, for example, exist when it is constituted only by one of its main metaphysical parts, namely the soul.65

In other words, a person is not identical to the parts that constitute him. Consequently, a difference in the identity of his parts does not necessarily imply a difference in the identity of the whole, in his identity. It is therefore possible for the individual to lose and gain parts while remaining identical through these changes. This, of course, is consistent with my reading of Thomas. Stump diverges

64 In Aquinas, Stump does not employ this same argument. Instead, her principal argument seems to be that Thomas attributes the characteristics of human individuals to disembodied souls, so those souls must constitute human persons. See Aquinas, pp. 52-53. 65 Aquinas, p. 53.

144 only in this critical respect: she holds that at least one kind of individual substance, a human being, can lose all its matter at once and remain the same individual.

A number of philosophers now hold positions akin to Stump’s on the role of substantial form in diachronic identity.66 Part of the attraction of this view—as Stump herself notes—is that it is rather difficult to explain what a separated human soul is if not a human being.67 However, it may be acceptable to categorize a separated human soul as a sort of sui generis substance in light of the uniqueness of human death and resurrection.68 I will set that interpretive question aside because it does not bear directly on the present inquiry. Another reason to accept Stump’s position, more pertinent to the inquiry at hand, was mentioned above: prime matter has no individuality and no features of its own, so substantial form alone would appear to be responsible for the individuality of a substance. Although I have addressed this subject already, I will revisit my response briefly in light of Stump’s concerns.

It is very straightforward to refute the form theorist’s claim with Thomas’s texts. As we have seen, he repeatedly states that form and matter are the principles of identity. He also is clear that the annihilation of a substance’s matter causes it to cease to exist as numerically the same even if its form persists. For instance, he describes a hypothetical scenario in which a fire retains the same

66 See, for example, Brown, Aquinas and the Ship of Theseus, pp. 118-24; and David Oderberg, Real Essentialism (London: Routledge, 2008), ch. 10. 67 Stump, “Resurrection, Reassembly, and Reconstitution,” pp. 155-157. 68 At least one text indicates that Thomas regards the separated human soul as a unique sort of substance. See Super Boetium De Trinitate pars 2, q. 4, a. 2, co. 6: “Dico autem in quantum huiusmodi propter animam rationalem, quae quodammodo ex se ipsa est hoc aliquid, sed non in quantum forma.” See also ST I, q. 75, a. 2, ad 1.

145 substantial form despite the annihilation and instantaneous replacement of its matter. In such a scenario, he notes, the fire does not remain numerically the same.69 Therefore, not only form but also matter is necessary for diachronic identity.

Stump raises another series of points that it is instructive to address. In arguing against the coherence of the corruptionist view, she repeatedly touches on the existence of the human person after death. She poses several questions to the corruptionist. First, she inquires whether the separated soul ceases to exist at the resurrection when the human person is restored to existence (on the corruptionist view). She further asks why God should reward or punish the separated soul, which—on her reading of corruptionism—has only come into existence after death. Finally, Stump questions the consistency of the corruptionist view with Thomistic texts that speak of the experiences of various individuals after death and before the resurrection.70

Each of Stump’s questions attacks a belief that she attributes to the corruptionists, namely that the existence of the separated soul is distinct from the existence of the human person. This is a troubling view, for it implies that there is no one thing that exists continuously from earthly life through death and into the resurrected state. Thomas also sees this view as worrisome, and he frames it as an objection in the Sentences Commentary:

69 See Quodlibet 8, q. 3, ad 2. Note especially: “Quia non tota materia similiter a forma abstrahitur, ut alia tota simul formam accipiat: haec enim generatio esset et corruptio; sicut si totus ignis unus extingueretur, et alius totus accenderetur.” 70 Stump, “Resurrection, Reconstitution, and Reassembly,” pp. 156, 157, 160.

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It seems that the same man will not rise, for the Philosopher says in Chapter 2 of On Generation and Corruption, “All things that have a nature subject to the motion of corruption will not return the same in number.” But such is the substance of man in his present state. Therefore, after the change of death he will not be able to return the same in number.71

In his reply to this objection, which we will discuss further shortly, Thomas clarifies that that alleged problem with corruption is that it implies a rupture in existence. A thing that dies ceases to exist, so anything that takes its place, such as a soul, must have a new existence. Stump, identifying a similar problem with corruptionism, rejects this view and then accepts what seems to be the only alternative: the continued existence of the human person is guaranteed by the persistence of the human substantial form, the soul, which is nonetheless not identical to the person. As Stump sees it,

Socrates the individual continues to exist because his soul continues to exist. On her view, the corruptionists must deny that there is any continuity of existence if they deny that Socrates ceases to exist.

Although I do not speak for any corruptionists, they certainly are not forced to embrace the view attributed to them by Stump; nor must they accept her view. This is because Thomas himself does not claim that the human soul has an existence distinct from the human person. He also does not claim that form on its own supports the continued existence of the human person. He instead offers something subtler: the separated soul retains the same esse that was present in the pre-mortem human being. Here is his explanation from the Sentences Commentary:

71 In IV Sent., d. 44, q. 1, a. 1, qc. 2, arg. 1, ed. Vivès 295. “Videtur quod non sit idem numero homo qui resurget. Sicut enim dicit philosophus, II de generatione, quaecumque habent speciem corruptibilem motam, non reiteratur eadem numero. Sed talis est substantia hominis secundum praesentem statum. Ergo post mutationem mortis non potest reiterari idem numero.”

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Rather, it should be said that the form of other generable and corruptible things is not self-subsisting, so that after the corruption of the composite it should remain, as is the case with the rational soul. The esse of the latter is received by the soul itself in the body and remains after the body goes. The body is brought to partake of this esse through the resurrection as there is not one esse of the body and another of the soul in the body. Otherwise, the union of the body and the soul would be accidental.72

In other words, the existence or esse of the separated soul is the same as the existence of the matter- form composite in its pre-mortem and resurrected states. Nonetheless, the persistence of this esse in the separated soul does not mean that the individual substance or matter-form composite continues to exist. Rather, the composite corrupts, as Thomas acknowledges, but the being (esse) of the composite remains in the soul. The preservation of the composite’s esse allows the composite to enjoy the same act of existence at the resurrection as it did during earthly life. Form theorists may find this to be a counterintuitive solution, but it is evidently Thomas’s view.

The foregoing passage from Thomas illustrates that he shares Stump’s concerns but addresses them in a manner somewhat different from hers. She relies on the persistence of the separated soul as the guarantor of pre-mortem and post-resurrection identity. Thomas also needs the separated soul to persist for his theory to work, but he additionally requires the preservation of the esse of the composite in the soul. The soul is indispensable because it receives the esse of the composite; however, the esse also is required for the numerical identity of the pre-mortem and post-resurrection

72 In IV Sent., d. 44, q. 1, a. 1, qc. 2, ad 1, ed. Vivès 298. “Vel dicendum, quod aliorum generabilium et corruptibilium forma non est per se subsistens, ut post compositi corruptionem manere valeat, sicut est de anima rationali, quae esse, quod sibi in corpore acquiritur, etiam post corpus retinet, et in participationem illius esse corpus per resurrectionem adducitur, cum non sit aliud esse corporis et aliud animae in corpore; alias esset conjunctio animae et corporis accidentalis.” This same teaching is repeated in SCG IV, c. 81, n. 11.

148 individual. Thomas expresses the requirement for the persistence of esse thus: “Things that are the same in number are the same in being [esse].”73

This examination of Thomas’s writings demonstrates that we cannot take the substantial form alone as the principle of diachronic identity. That position would be contrary to Thomas’s repeated claim that matter is also necessary for identity; it would further ignore the role he assigns to esse in enabling the identity of the earthly individual with his resurrected self. Form theorists, then, recognize only part of what is needed for diachronic identity.

Esse as the Principle of Identity Because the preservation of esse is necessary for human identity before death and after the resurrection, one may wonder if esse is in fact the principle of identity, or at least a co-principle along with matter and substantial form. It seems fitting that a necessary ingredient of diachronic identity would be a principle of identity. Although Thomas never names esse as such a principle, perhaps one should read this intention into his thought.

Apart from this consideration, there may be other reasons to posit esse as a principle of diachronic identity. Jorge Gracia has argued that esse is the appropriate principle of identity within Thomistic metaphysics because it alone exhibits two features: 1) being essential or necessary for a creature’s

73 SCG IV, c. 80, Leon. 15.251: 4-5. “Quae enim sunt eadem numero, secundum esse sunt idem.”

149 being what it is, and 2) radical particularity, or individual status by its very nature.74 Gracia’s claim deserves some attention because it conflicts with the entirety of this chapter. He defends it primarily by disqualifying all other candidates for the principle of identity, so I will examine his objections to each rival before turning to his arguments in favor of esse.

Gracia names and rejects four candidates for the principle of identity: matter, form, accidents, and material substance itself. By this last he appears to mean the composite of form and matter, though he does not say so explicitly.75 It is worth discussing each argument in some detail to understand precisely why Gracia turns to esse as the proper principle of identity in Thomistic metaphysics.

He first argues that matter cannot be the principle of identity for several reasons. The premise underlying his arguments is the following: “The principle of identity must be individual of itself and unchanging in order to account for numerical sameness through time.”76 As Gracia explains, matter considered apart from particular, determinate dimensions cannot account for an individual’s existing here and now, for such matter is itself not individual or determinate; rather, matter is common. But remaining this individual presupposes being some individual, so a principle of identity must account for the individuality of a substance. Because it fails to do so, matter apart from determinate quantitative dimensions cannot be the principle of identity. However, if one follows Thomas and adds determinate dimensions to matter to explain individuation, one must look elsewhere for a principle

74 Jorge Gracia, “Numerical Continuity in Material Substances: The Principle of Identity in Scholastic Metaphysics,” Southwest Journal of Philosophy 10 (1979), pp. 79, 88. 75 Gracia, “Numerical Continuity in Material Substances,” pp. 83-84. 76 Gracia, “Numerical Continuity in Material Substances,” p. 82.

150 of identity, Gracia claims. Although matter under determinate dimensions may individuate, such quantified matter cannot guarantee that the individual remains this individual because quantitative dimensions change frequently. Gracia further reasons that the doctrine of the resurrection requires a principle of identity other than matter. If one took matter to be the principle of identity, then the corruption of the body would prevent men from being identical before death and after the resurrection. However, according to Gracia, a human remains identical throughout these events, so matter is not the principle of identity.77

Form, on Gracia’s view, cannot be the principle of identity for two reasons. First, it is not particular of itself. Therefore, formal identity is not numerical identity; indeed, identity of form guarantees only identity of kind, not individual identity. Second, form is unsuitable as a principle of identity because it is “not the ultimate principle of being or existence in an individual.” He explains that “form does not have being in and of itself... [and] therefore has none of the ontological features to secure individual unity, since it has no being—which it receives from esse.” 78 Gracia’s point rests on

Thomas’s claim that forms, considered in abstraction from their instances, can exist either in individuals or in the mind (as universals). This openness to different modes of existence, Gracia seems to think, means that any instance of a form must receive its individual mode of existence—its

“being and unity”—from another source, namely esse and matter. Therefore, he concludes that “to

77 Gracia, “Numerical Continuity in Material Substances,” pp. 81-82. 78 Gracia, “Numerical Continuity in Material Substances,” p. 87.

151 say that form is the principle of identity would at least remain mysterious and at most be contradictory.”79

Gracia also objects to the claim that accidents individuate on several grounds. Because I am not defending this claim in any form, I will summarize Gracia’s objections briefly. First, he notes that sameness of accidents always depends upon sameness of the substances possessing those accidents, so accidental sameness cannot be the foundation of identity of a substance. Second, substances remain the same in spite of accidental change, and the search for a principle of identity is a search for some factor underlying this phenomenon. Similarly—and most decisively in Gracia’s view—we cannot claim that something is the same in light of any mutable constituent, but accidents are such mutable constituents.80 Therefore, accidents cannot serve as the principle of identity.

Gracia disposes of substance itself as a principle of identity as well. Because Thomas uses the term

‘substance’ in a few different ways, one would hope that Gracia would explain how he is using it.

Within a Thomistic framework, he could be referring to the individual or supposit, the substantial form, or the essence including both matter and form.81 Because Gracia calls the substance

“individual in and of itself” within nominalist frameworks, he appears to equate substance with the individual rather than the substantial form or essence. In any case, his primary objection to substance as the principle of identity is that substance, on Thomas’s view, is not individual of itself.

79 Gracia, “Numerical Continuity in Material Substances,” p. 87. 80 Gracia, “Numerical Continuity in Material Substances,” pp. 85-86. 81 On the senses of substance in Thomas’s metaphysics see Wippel, The Metaphysical Thought of Thomas Aquinas, pp. 201- 203.

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Rather, it consists of components that make it an individual. Consequently, we must look to these components, not to substance, to locate the principle of identity. However, as we have seen above, three of the chief components of the substance—its matter, form, and accidents—are not individuals of themselves either. Therefore, in Gracia’s opinion, neither substance not its primary constituents account for identity through time.82

Having dispatched with the chief candidates for the principle of identity, Gracia singles out one overlooked alternative as the best option: esse. According to Gracia, esse alone exhibits the essentiality and inherent particularity required of a Thomistic principle of identity. On the first point, Gracia explains that essentiality means “both what is commonly called essential, a matter of form, and existential, a matter of existence.”83 It is quite obvious that esse is a principle of existence, but is

Gracia correct to consider it essential as well? He believes so because Thomas teaches that a substance’s esse comes to it through its substantial form. Although Gracia is correct that esse is received by substantial form, it is unclear why this fact should qualify esse as essential. Notably, as we have seen above, Thomas considers only matter and form—not esse—to be essential principles.

Gracia’s claim that esse is particular of itself is also unsupported by Thomas’s writings. The two passages that he cites in support of this claim do not offer any clarification. One, an excerpt from

Thomas’s Commentary on Aristotle’s Metaphysics, is a general discussion of unity and plurality that does not mention esse. The other, from the Prima Pars of the Summa theologiae, states that esse is

82 Gracia, “Numerical Continuity in Material Substances,” pp. 83-84. 83 Gracia, “Numerical Continuity in Material Substances,” p. 88.

153 received by substantial form, which together with matter makes the substance a unity. This second passage in fact seems to contradict Gracia’s claim, for it attributes the unity of a substance to matter and form, not to esse.84

It should now be clear why Thomas does not consider esse to be a principle of diachronic identity: he considers diachronic identity to mirror synchronic identity. In Thomas’s metaphysics, matter and substantial forms are the only determinants of synchronic identity, so they are also the only principles of diachronic identity. However, esse is needed for diachronic identity because it is necessary for an object’s existence, and, of course, an object cannot continue to be the same without continuing to be.

Now, in at least one text Thomas speaks as though esse could function as a principle of identity. The text spans chapters 80 and 81 of SCG IV, where Thomas addresses various objections to the resurrection. The beginning of the passage in question is the following objection:

Whatever is not continuous does not seem to be numerically the same. This is clear not only in sizes and motions, but also in qualities and forms. Thus, if after being healthy a person becomes sick and healthy again, the state of health does not return numerically the same. It is clear that human esse is lost through death because corruption is a change from existence [esse] to non-existence [non esse]. Therefore, it is impossible for the esse of a human to return the same in number. Consequently, neither will the human be the same in number, for things that are numerically the same are identical in their esse.85

84 Gracia, “Numerical Continuity in Material Substances,” p. 88. 85 SCG IV, c. 80, Leon. 15.251. “Quod non est continuum, idem numero esse non videtur. Quod quidem non solum in magnitudinibus et motibus manifestum est, sed etiam in qualitatibus et formis: si enim post sanitatem aliquis infirmatus, iterato sanetur, non redibit eadem sanitas numero. Manifestum est autem quod per mortem esse hominis aufertur: cum

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Here the objector first argues that the discontinuity of esse impedes the numerical identity of individual substances (and, indeed, of individual accidents). He then contends that humans cannot be numerically identical before and after death because esse is interrupted by death. In his reply,

Thomas appears to accept the first claim but not the second:

What is argued in the third objection—that the esse is not one because it is not continuous—relies on a false premise...The esse of the soul, which was the esse of the composite, remains in the soul when the body disintegrates. When the body is restored in the resurrection, it is brought back to the same esse that remained in the soul.86

We are told that the discontinuity of esse is not an obstacle to the resurrection because esse is in fact continuous, preserved in the separated soul. Notably, Thomas does not dismiss the claim that such a discontinuity would frustrate numerical identity if it did occur. It thus seems reasonable to conclude that continuity of esse is a condition for numerical identity. Does this mean that esse is also a principle of diachronic identity?

To determine whether esse is a third principle of diachronic identity, we should consider two different roles that esse might play in preserving identity through time. The first role is that of a direct guarantor of numerical identity. In this function, the discontinuity (non-identity) of esse precludes the diachronic identity of a substance independently of any differences in substantial form and matter. True, a

corruptio sit mutatio de esse in non esse. Impossibile est igitur quod esse hominis idem numero reiteretur. Neque igitur erit idem homo numero: quae enim sunt eadem numero, secundum esse sunt idem.”

86 SCG IV, c.81, Leon. 15.253. “Quod vero tertio obiicitur, quod esse non est unum quia non est continuum: falso innititur fundamento...Esse igitur eius, quod erat compositi, manet in ipsa corpore dissoluto: et reparato corpore in resurrectione, in idem esse reducitur quod remansit in anima.”

155 discontinuity in a substance’s esse would always also result in the non-identity of its form and matter over time, but we are abstracting from that fact in this scenario. If esse plays the second role, in contrast, it preserves a substance’s identity only indirectly. Only by providing continued existence to substantial form and matter and so allowing them to remain the same does esse play any role in identity. On the second view, the persistence of esse does not make a unique contribution to the persistence of the substance apart from enabling form and matter to remain the same.

If the first of the two views above holds true, then esse should be considered a third principle of diachronic identity. In this situation, the persistence of esse would play exactly the same role as the persistence of substantial form and matter: it would contribute directly to a given substance’s being numerically the same substance at time t and at a later time t'. If the second view is true, however, then esse would not count as a principle of identity. Instead, the persistence of esse would simply be a condition for diachronic identity, a state of affairs that ensures the persistence of the two actual principles of identity. Esse itself would not contribute to identity but to the preservation of form and matter.

Thomas’s texts do not explicitly indicate his support for one view or the other. Nonetheless, there are reasons for Thomists to deny that esse is a principle of diachronic identity. Chief among these reasons is the parallel between synchronic identity and diachronic identity. As we have seen, there is reason to ascribe to Thomas the view that the principles of synchronic identity are also the principles of diachronic identity. To review briefly, the principles of synchronic identity are

156 substantial form and matter. These principles account for Plato’s being Plato and Socrates’ being

Socrates; each man is who he is because he has this matter and this substantial form. To be sure, each man also requires esse to exist as Plato or as Socrates, but esse does not determine either to be this particular man. In the case of diachronic identity, esse ensures that the substantial form and matter continue to exist and continue to make these individuals the individuals that they are. Yet esse does not make Socrates to be Socrates across time any more than it makes him Socrates at a given instant.

If this parallel can be attributed to Thomas—and the review of texts in this work suggest that it can—then esse does not serve as a principle of identity. Its functions align with the second role described above.

A second consideration in favor of the second view is the consistent emphasis in Thomas’s texts on the importance of essential principles for identity through time. As we have seen, he repeatedly mentions that the persistence of essential principles is necessary for numerical sameness. Although he could add in these same passages that the sameness of esse is necessary as well, he does not.

Thomas mentions that esse remains the same only to rebut the claim that the human soul does not persist after death. The human soul’s unique relationship with esse enables it, unlike other substantial forms, to survive the corruption of the composite.87 If Thomas held that esse were a principle of identity, he could state so explicitly in any instance where mentions that diachronic identity requires the identity of the essential principles. However, he does not. Instead, he discusses esse only to assure the reader that one of the principles in the case of humans, namely the soul, can persist after death.

87 See SCG IV, c.81, Leon. 15.253. “Differt tamen quantum ad hoc anima rationalis ab aliis formis. Nam esse aliarum formarum non est nisi in concretione ad materiam: non enim excedunt materiam neque in esse, neque in operari. Anima vero rationalis, manifestum est quod excedit materiam in operari: habet enim aliquam operationem absque participatione organi corporalis, scilicet intelligere. Unde et esse suum non est solum in concretione ad materiam.”

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The consistent emphasis on form and matter, coupled with the limited attention given to esse, suggests that esse does not play the same role as the former two constituents.

Before concluding the treatment of esse, Gracia’s arguments against form and matter as principles of identity deserve a further look. Is he correct that both lack the particularity required of a principle of identity? To answer this, it is first necessary to consider in what way particularity is needed for diachronic identity. Gracia’s view is that the particularity or individuality of the principle of identity is required to explain why an individual substance remains this individual substance. If the principle of identity is not particular, it cannot account for a substance’s being this substance. This view seems correct to me in this respect: whatever explains why a substance is the same one thing must itself remain the same one thing. Gracia further appears to contend that the principle of identity must be the ultimate source of both particularity and formal or essential sameness. This assumption behind this claim appears to be that a principle that has some further source of its particularity or essential identity would have its own principle of identity in this source, which would be the true principle of identity for the individual substance. This reasoning also appears sound to me, but, as I shall explain, it does not rule out form and matter as candidates for the principle of identity.

Although I accept Gracia’s criteria for the principle of identity (with the qualification just mentioned), my evaluation of candidates for this principle differs from his. Specifically, he is incorrect in saying that form and matter lack the particularity required of a principle of identity. His mistake lies in considering these two principles separately rather than jointly. A substantial form, it is true, lacks particularity insofar as it is not the source of its own particularity; however, forms always

158 exist as particular when in matter. Matter, as we have discussed above, does in fact have a sort of individuality or particularity of its own. Matter has no further source of its particularity, and a substantial form is particular in virtue of being received in matter. Esse does not cause this particularity in either case.

In short, form and matter taken together do not lack the features that Gracia requires of a principle of identity. Furthermore, esse is unsuitable as a principle of diachronic identity because it is not a principle of synchronic identity. We can therefore be confident that Thomas has not made a fundamental, obvious mistake in naming form and matter as the principles of identity.

Conclusion Thomas’s theory of identity establishes the essential principles of a substance as its principles of diachronic identity. These principles, substantial form and matter, must remain the same for an individual to preserve its numerical identity. However, the ways in which they remain the same are different, and so their functions as principles of identity are dissimilar as well. While the identity of form is a brute ontological fact, the sameness of matter requires the sameness of basic functional parts resulting from union with an individual’s substantial form. Because this sameness is not particle-for-particle material identity, it may be less misleading to speak of continuity rather than identity of matter. This continuity also requires an “overlap” at the particulate level so that at any instant a substance retains some particles that it possessed at the prior instant.

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Whether this theory of diachronic identity is an improvement over contemporary endurantist theories remains to be seen. The following chapter will argue that Thomas’s view of identity, founded on a sophisticated ontology of material objects, has the resources to address the problems that beset today’s endurantist views.

CHAPTER 4: THE PROBLEMS OF DIACHRONIC IDENTITY RESOLVED

Chapter 3 presented my interpretation of Thomas Aquinas’s thoughts on diachronic identity. The theory that I distilled from his writings I will henceforth refer to as “hylomorphic endurantism,” or

HE for short. This chapter will argue that HE is superior to other endurantist theories and that it satisfactorily addresses longstanding problems about diachronic identity. To avoid any confusion about the tenets of HE, it will be useful to enumerate its fundamental claims:

1. All individual material substances are composed of a substantial form, prime matter

configured by the substantial form (second matter), esse, and accidental features.

2. The synchronic identity of individual material substances is determined by the substances’

substantial forms and the matter configured by the forms. Substance a is numerically the

same as substance b if and only if they have numerically the same substantial form and

numerically the same second matter.

3. As with synchronic identity, the diachronic identity of individual material substances

depends on substantial form and second matter. For a substance to remain numerically the

same over time, it must have numerically the same substantial form. In addition, the

substance’s matter must be continuous: at any instant in the substance’s existence (aside

from the first moment of its existence), the substance must include some matter that was

also part of the substance at the immediately preceding instant. Moreover, the parts of any

substance a must perform the same kinds of functions at time t as the parts of a performed

at time t-1.

4. Accidental features are irrelevant to synchronic and diachronic identity.

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HE’s merits are of two kinds. First, there are the features that differentiate HE from other forms of endurantism. Specifically, the theory offers an ontological foundation for its claims and develops the concept of whole presence much more fully than other endurantist theories. From these two advantages follow a second reason for favoring HE, namely its superior solutions to problems concerning diachronic identity. Because the latter merit arises from the former, it makes sense to begin with a fuller discussion of the distinguishing features of the theory.

Ontological Explanation in HE It is easy to locate HE’s main point of departure from its rivals. No other endurantist theory rests upon the foundation of a preexisting metaphysical system. All the important concepts in HE—form, matter, accidents, substances, and esse—play roles in Thomistic metaphysics independently of their roles in diachronic identity. The Thomist has this conceptual apparatus at his disposal when confronted with puzzles about diachronic identity. He therefore has resources to solve the puzzles ontologically and independent motivation for the ontological elements of those solutions. The case is otherwise with other endurantists: they come to these problems with few if any metaphysical commitments—nothing in comparison to the vast Aristotelian-Thomist framework. Although these philosophers have less metaphysical baggage to justify, they also must improvise solutions to each new problem. Because they have little ontology with which to work, they turn chiefly to logical and semantic solutions, such as Merricks’ approach of “taking tense seriously.” Admittedly, a few philosophers, such as Peter van Inwagen, do expand their metaphysics on the nonce, but they do not draw on claims that they have previously defended at length.

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HE’s use of preexisting resources has two important—in fact defining—consequences. The first is that the theory offers an account of what it is for a substance to be numerically the same over time.

In other words, it offers a criterion of diachronic identity. Recall from chapter 1 that this is not an analysis of the phenomenon of identity itself. Rather, HE provides an explanation of the identity of complex entities—material substances—in term of the identity of simpler entities. This does not and cannot happen in other endurantist theories because they have no underlying ontological framework that posits and describes such simpler entities.

As a consequence of their lack of ontological frameworks, there is no ontologically grounded explanation for contemporary endurantists. They cannot tell us that a substance is numerically the same so long as it retains a certain sort of constituent. Only if they devise their own theories of the structure of substances would this be possible. Merricks, of course, rejects the possibility of such an attempt; I have already discussed how this rejection is unfounded. It is unclear whether Peter van

Inwagen disagrees with Merricks on this point, but van Inwagen lacks a theory of substantial structure on which to draw should he wish to do so. Thus, neither of them offers an account of what it is for a substance to be the same over time. Merricks says this is impossible, while van

Inwagen’s exposition of endurantism avoids the question of what it is for an object to remain numerically the same.1 These and other such endurantists are left to argue dialectically against perdurantism.2

1 See “Four-Dimensional Objects,” Noûs 24:2 (1990), pp. 248-252. 2 This critique does not touch some other endurantists I have mentioned in this work, including Brower, Oderberg, and

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The specific way in which HE provides an account of diachronic identity deserves some further attention. In short, HE explains the diachronic identity of the whole in terms of the diachronic identity of the parts. To be numerically the same substance is to have numerically the same substantial form and matter that is “continuous” across time. This is not an analysis of identity per se, but an analysis of the identity of a material substance specifically. The analysis of substantial identity in terms of the identity of essential principles is a defining aspect of HE. Furthermore, this aspect is an illustration of the point above: HE looks for an explanation of substantial identity and it finds resources for that explanation in the essential principles of Thomistic ontology.

Readers reflecting on this differentiator of HE may notice the appearance of a problem. If the identity of substantial form and matter accounts for the identity of a substance, then on pain of circularity those constituents must have their identities independently of the substance. Yet this does not seem to be the case. This substantial form would seem to be this individual form because it is part of this material substance. Likewise, matter appears to be this matter because it belongs to this individual. On this supposition, one might think that the essential principles would not be the same apart from the individual substance that they compose. Thus, the parts that confer identity on the substance seem to depend on the substance for their identities.

Stump. Notably, these philosophers are all Thomist-Aristotelians, so they can (and do) help themselves to Thomist- Aristotelian ontological resources.

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To sketch out the problem more clearly, there are two incompatible propositions under consideration:

1. The identity of the substance is ontologically prior to the identity of its substantial form and

the continuity of matter.

2. The identity of a substantial form and the continuity of matter are ontologically prior to the

identity of the substance.

The notion of ontological priority or dependence here requires a bit of explanation. Broadly, if x is ontologically prior to y, then the existence of x (if y is an object) or fact that x obtains (if x is a state of affairs) accounts for y’s existing or obtaining. There are various types of ontological dependence, but we do not need to delve into them here.3 It is sufficient to realize that proposition 1 above states that a substance’s identity accounts for the identity of its substantial form and the continuity of its matter; proposition 2 states the converse. Importantly, ontological dependence is asymmetric, so (1) and (2) cannot both hold true. Thus, it is critical to determine whether HE contradictorily implies that both are true.

Determining which of the two propositions HE holds requires a return to the basics of substantial composition, generation, and corruption outlined in the previous chapter. For the sake of

3 For a brief review, see Tuomas Takho, “Ontological Dependence,” Stanford Encyclopedia of Philosophy, 2015. Available online at http://plato.stanford.edu/entries/dependence-ontological/#VarOntDep.

165 illustration, I will turn to an example of an individual substance, Koko the gorilla. According to HE,

Koko is a composite of a substantial form and matter. She first came into being when her parents mated. In this process, Koko’s substantial form was educed from appropriate preexisting matter, that is, the matter of her parents’ gametes. Importantly, this preexisting matter was not Koko’s matter, though it would later be incorporated into her matter. The educing of Koko’s form, the generation of Koko as a substance, and the incorporation of preexisting matter into the substance—

Koko—all took place simultaneously. Accordingly, Koko, her substantial form, and her matter all came into being at once. Thomas makes this point about the origin of essential principles throughout his work and quite concisely in his commentary on Aristotle’s Metaphysics:

Strictly speaking, forms do not come to be, but they are educed from the potency of matter insofar as matter, which is in potency to form, comes to actually be subject to a form—and this is the production of a composite.4

Substantial forms begin to exist at the same time as their composites come to be. Furthermore, although prime matter does not come into existence, it does become subject to a substantial form so that matter informed by a substantial form, such as the matter of a gorilla, exists only so long as the substantial form exists. Temporally, then, there is no problem of priority.

There is however, ontological priority in the following sense: Koko is this gorilla because she has this substantial form and this matter. Without these two principles, she would not be the gorilla that she is. Chapter 3 produced the texts in support of this position, so I will not reiterate them here.

4 In Aristotelis libros Metaphysicorum – lib. 7, l. 7, n. 1423, ed. Marietti 349.9. “Formae enim proprie non fiunt, sed educuntur de potentia materiae, inquantum materia quae est in potentia ad formam fit actu sub forma, quod est facere compositum.”

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Therefore, HE holds (2).

Does HE hold (1) as well? As the reasoning above makes clear, it does not. The identities of form and matter depend on the identity of the substance in this sense: if the substance corrupts and so ceases to exist, the substantial form and matter cease to exist as well. However, this is merely logical dependence of the essential principles on the substance; the corruption of a substance implies the destruction of its essential principles, but this is so only because corruption just is the dissolution of these principles. The principles do not depend ontologically on the substance for their existence or identity: the existence of the substance does not account for the principles existing or being these individual principles.

Readers familiar with the Aristotelian view of parthood may suspect a contradiction here. Aristotle and his followers, including Thomas, argue that parts of substances derive their existence and identity from the identity of the substance. A rabbit’s foot, for instance, is only truly a rabbit’s foot when it is part of the body of a living rabbit. A severed rabbit’s foot kept as a good luck charm is only equivocally a rabbit’s foot; it is really a collection of numerous substances.5 Aristotelians hold this view because they understand being a foot as a functional property, that is, the property of serving a certain role in a living organism. When an object ceases to function accordingly, it is no longer a member of the kind “foot.” The same holds for all other substantial parts, such as limbs, organs, and

5 For Aristotle, see Politics I.1253a20-23. For Thomas’s statement of this Aristotelian doctrine, see, for example, In III Sent., d., 6 q. 3, a. 1, co.

167 other kind-specific parts.

Essential principles are critically different from substantial parts in this respect. Unlike substantial parts, essential principles do not derive their identity or existence from the substance. Rather they are the source of identity and existence of the substance itself. To repeat what chapter 3 expounded, the identity of an individual is determined by its essential principles. Moreover, Thomas frequently states that the esse or being of substance comes to it through its substantial form. The situation with substantial parts is just the opposite: they receive existence and identity from the substance.

Consequently, the essential principles are not ontologically dependent on their substances even though substantial parts are.

A second consequence of HE’s use of Thomistic ontology concerns the theory’s understanding of numerical identity. HE employs the Thomistic system to provide an account of numerical identity that is not “strict.” That is to say, HE countenances diachronic numerical identity that does not abide by Leibniz’s Law. HE can do so because it draws on Thomas’s account of what it is to be an individual substance. By omitting accidents and specific physical parts from the account of substantial identity, Thomas allows for numerical identity of the substance without numerical identity of the substance’s properties over time. No non-Thomistic version of endurantism advances this understanding of numerical identity, but, as we shall see later, it is an indispensable benefit of HE.6

6 Both Stump and Oderberg, who are Thomists, defend the numerical identity of substances without the numerical

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Whole Presence Explained Belief in whole presence is the defining claim of endurantism. Ironically, it is also the murkiest concept in most endurantist theories. For most contemporary endurantists, such as Merricks and van Inwagen, whole presence is a negative concept, the mere rejection of temporal parts. Seemingly, the nature of whole presence is so self-evident as to need no further positive explanation. Yet the protests of perdurantists, who claim to find whole presence mysterious, suggest that a more substantive explication of the concept is needed.

As I noted at the outset of this chapter, HE is the only endurantist theory with a substantive account of whole presence. It is now time to provide that account. First, there is a synchronic form of whole presence: to be wholly present at a time t is to exist as a complete individual substance, possessing both essential constituents (substantial form and matter) and constituents that are not part of the essence (proper accidents, other accidents, and esse). HE defines diachronic whole presence in terms of synchronic whole presence, namely as 1) the presence of an individual substance (including essential parts, accidents, and esse) and 2) the numerical identity of that substance, given by the numerical identity of its substantial form and the continuity of its matter. Importantly, being wholly present across a span of time entails being numerically identical as well: A substance that is wholly present from time t to time t' has numerically the same form during that span of time and its matter remains “continuous” throughout that span. Notably, this view of whole presence does not require

identity of their properties. For Stump, see the passages quoted in the following pages. For Oderberg, see “Hylemorphic Dualism,” in Personal Identity, ed. Ellen Frankel Paul, Fred Miller, and Jeffrey Paul (Cambridge: Cambridge University Press, 2005), pp. 80-81.

169 that accidents and physical parts remain numerically the same.

There are several points that favor this understanding of whole presence. Before enumerating these, however, it is logical to turn to a pointed question about the view I have sketched: Where is the whole in the Thomistic of whole presence? The objection lurking behind this question is the following: A material substance has physical parts and accidents at every moment of its existence.

This is simply part of being a material substance. Now, if such a substance is not identical with respect to every part and accident at every time, it would seem that the whole of the substance is not present at every moment of its existence. Rather, just some parts of the whole are present. Consider the example of a transplant patient who has a heart at t1, lacks a heart at t2, and has a new heart at t3. At t2 he exists without parts that are his at t1 and t3, so he does not exist as a whole at t2.

Furthermore, the whole at t1 is not the same as the whole at t3. Nonetheless, he qualifies as being wholly present on the HE view. Accordingly, the objection goes, HE should relinquish the term

‘whole presence.’

There are two strands of reply to this objection. The first is that the primary function of the term

‘whole presence’ is to draw a contrast between perdurantism and endurantism. Recall that within the perdurantist framework the whole is a space-time worm that spans multiple instants of time. At any instant, the worm is only partially present (assuming that it exists at more than one instant). The endurantist, who rejects the existence of such worms and their temporal parts, denies the possibility of partial presence. He thereby may be said to endorse a theory of whole presence, but this conception of whole presence is negative; at least, its positive content is undetermined. HE certainly

170 offers a theory of whole presence in this minimalist sense, but it offers more as well.

By way of a second rejoinder, the defender of HE can note that according to his theory the whole individual persists, but in a manner quite different from what perdurantism supposes. Differentiating among three concepts helps clarify HE’s notion of whole presence. The first is the notion of being wholly persistent, or being identical part-for-part and property-for-property through time. This is, in other words, immutability or “strict identity.” Some perdurantists, such as Lewis, have understood whole presence in this fashion, but it is by no means the only understanding. The second concept is numerical identity through time. HE understands the numerical identity of a substance in terms of the numerical identity of its substantial form and continuity of its matter; this identity does not involve being wholly persistent or strictly identical through time. There is finally the notion of whole presence, the idea that an individual is “all there” at any given instant rather than being a part of a temporally extended whole. The first two notions are both candidates for the role of whole presence. Is either an acceptable candidate?

Whole presence must be very different from whole persistence and something more than numerical identity. Because endurantism holds that substances persist through changes of parts and properties,

HE cannot claim both that whole presence is whole persistence and that whole presence applies to all or most material substances. Clearly most material substances are not wholly persistent: they continually lose and gain parts and properties. However, whole presence is supposed to apply to all material substances on the endurantist’s view. Thus, the two notions cannot be the same. Turning to numerical identity, this concept seems to fall short of what is needed in whole presence, for HE

171 characterizes numerical identity in terms of the persistence of the essential parts of a whole. The essential parts, however, are not themselves the whole, and they never exist without some further parts and properties. So whole presence cannot be merely the sameness or persistence of essential parts. There must be some further accounting for the non-essential (accidental) parts in the notion of whole presence.

Although numerical identity is not equivalent to whole presence, it furnishes the key to understanding the latter concept. In the first place, diachronic numerical identity ensures that it is the same whole that is present at different times. In other words, to say that an individual substance is numerically identical over time is to say that the whole W at time t is numerically the same whole as W' at time t'. Further, if object O is not numerically the same at t and t', O cannot be wholly present at t and t'. Whole presence through time presupposes numerical identity through time. Yet whole presence also requires something more because an individual is more than its essential parts; it includes accidental features and esse.7 Any description of the whole of an individual at a given time, then, must include substantial form, matter, esse, and accidents. To be wholly present at a single moment is simply to possess all these components, to exist as a complete individual substance. To be wholly present across an interval is to be wholly present at each moment in that interval and to be numerically identical throughout.

The question most likely to arise from the foregoing descriptions is whether being wholly present

7 See the discussion of Leibniz’s Law in the next section for further explanation of this point.

172 across an interval requires possessing numerically the same accidental features through that interval.

From the comments on being wholly persistent above, it should be clear that the answer is “no.”

Whole presence does not amount to part-for-part, property-for-property sameness through time; it is not changelessness. This is because accidental features and parts play a role in being a whole (an individual substance) but do not account for diachronic identity. The entirety of any individual material substance always includes particular accidents and parts, but these particular accidents and parts may change while the substance remains numerically the same.

A perdurantist might express frustration with this view of whole presence with the following objection. Consider the case of Socrates, who is bearded at t and beardless at t'. If we schematize the wholes that are Socrates at t and t', we get something like the following by using the HE ontology:

For simplicity, call the whole that is Socrates at t W, and the whole that is Socrates at t' W'. Granting

HE’s claims about the conditions for numerical identity for the sake of argument, says the perdurantist, it is nonetheless clear that no whole persists unchanged from t to t', for W is not the same as W'. Therefore, there is no whole that endures and thus no whole presence through time.

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Furthermore, if one claims that Socrates = W and Socrates = W', but W ≠W', then the result is that

Socrates ≠ Socrates. This is another perdurantist way of saying that there cannot be numerical identity over time within an endurantist framework.

The HE rejoinder, anticipated above, is that this objection conflates being wholly persistent with being wholly present. The advocate of HE readily concedes that there is no collection of parts and properties that remains strictly identical through time. However, this form of identity is not at issue.

We have established already that Socrates the individual is numerically identical through time in virtue of the persistence of his substantial form and the continuity of the matter. Moreover, Socrates persists as a whole: at every instant in the interval from t to t' he possesses the full complement of substantial form, prime matter, accidents, and esse. These components, as noted in chapter 3, bear different relations to what Socrates is: some are essentially and necessarily part of what he is, but others are only contingently part of him. Because his relationship to some of his constituents is contingent, he can persist even as some of these change. The whole that endures, then, is Socrates himself—not the collection of his components.

The question of whether or not Socrates is identical to two non-distinct wholes, W and W', rests on an ambiguity about the concept of a whole. If one understands a whole as a collection of parts or components with no specified relations among these parts, then Socrates is not identical to any such whole. Socrates is not a collection of components but rather an individual who bears different relations to his different components. Therefore, HE never claims that Socrates is identical to two such different collections. However, Socrates is identical to (in other words, he is) another sort of

174 whole. This whole includes a substantial form and prime matter as essential components, necessarily includes certain accidents that result from Socrates’ essential components (proper accidents), and contingently includes non-necessary accidents. The identity of this whole depends on the identities of the essential parts but not on the identities of non-necessary accidents. If W and W' are wholes in the second sense, then the identity of each rests on the identity of the essential parts. These parts are the same in this example, so W and W' are numerically the same, differences in accidents notwithstanding.

There are important virtues of this view. Most significantly, it is a substantive account. HE characterizes the enduring whole in ontological terms so that one can say precisely what whole presence is. For the same reason, HE’s understanding of whole presence can be the subject of meaningful debate. Because HE defines whole presence positively and argues for it on the basis of a preexisting ontology, an objector can take issue with the underlying metaphysics or with HE’s use of this metaphysics in explaining whole presence. No other endurantist view has this merit.

Despite these merits, the perdurantist will likely protest that the view sketched above ignores

Leibniz’s Law and does violence to the very notion of identity. Reading Leibniz’s Law in a certain manner, it is tempting to say that the persisting whole encompasses all the ontological constituents of an individual. On this reading, the law requires that to be numerically the same an individual must be the same with respect to every feature at every instant of its existence. However, this reading is fundamentally hostile to endurantism because it implies that any change in properties yields a numerically distinct individual. Thus, any notion of whole presence that insists on the sameness over

175 time of features and properties would undermine the endurantist project. HE thankfully rejects such an interpretation of Leibniz’s Law, as I shall show shortly. Likewise, HE dispenses with the notion that numerical identity is simply property-for-property, part-for-part sameness. The HE view diverges radically from some understandings of numerical identity, so the perdurantist is justified in demanding further explanation. The next section will address this topic and the related subject of

Leibniz’s Law. The subsequent sections will describe in detail the Thomistic solutions to other standard puzzles about diachronic identity.

Leibniz’s Law Reframed To qualify as a plausible theory of diachronic identity, hylomorphic endurantism must explain how it is consistent with Leibniz’s Law, specifically the principle of the Indiscernibility of Identicals. Most philosophers accept the principle, and every theorist writing on diachronic identity addresses the principle as a matter of course.

The problem posed in chapter 1 concerning Leibniz’s Law was that a diachronic version of the law would impose requirements that seem never (or rarely) to be satisfied. Specifically, according to the law an object that remains numerically identical across an interval of time must possess all the same properties in that interval. Because any complex physical object is constantly undergoing many changes, it appears that nothing (or almost nothing) meets the requirements of the law.

Consequently, there are few (if any) instances of substantial numerical identity over time.

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One can attempt to resolve this problem by limiting Leibniz’s Law to synchronic cases, but this approach faces objections. In particular, Sider argues that there is no principled reason to restrict the law to synchronic applications. He writes: “Restricting Leibniz’s Law forfeits one’s claim to be discussing identity. The demands of the notion of the identity are high: identical things must share all their properties.” Part of identity, on Sider’s view, is possessing all the same properties. If one claims that synchronic identity involves possession of all the same properties but diachronic identity does not, then one is speaking about two distinct phenomena—identity and something else.

It should be clear that HE is compatible with the synchronic version of Leibniz’s Law but not with the diachronic version. HE states that substances that are numerically the same will have the same properties at a given instant t. However, an object O may remain numerically the same over time even though it gains or loses certain properties during that span. In this way, HE appears to contradict the standard reading of Leibniz’s Law defended by Sider and apparently accepted by some endurantists, such as Merricks.

Is there in fact a principled reason for the Thomist to reject the diachronic version of Leibniz’s Law, or is his opposition simple special pleading? There is indeed a foundation for this rejection, rooted in the theory of substantial identity. The Thomist holds that identity consists in having the same essential principles, namely substantial form and matter. It is the sameness of these principles, not the sameness of accidents, that underlies substantial identity synchronically and diachronically.

Although in the synchronic case there always is sameness of accidents, this does not have to hold true for identity in all circumstances, such as diachronic cases. As Eleonore Stump notes, Thomas

177 begins with the pre-philosophical datum that a thing can change its properties while remaining one and the same thing. She claims that the Thomistic analogue of the Indiscernibility of Identicals is this weaker principle:

(Aquinas’s Principle) (AP): For any x and y, x is identical to y only if, for any time t, x exists at t if and only if y exists at t, and if x exists at t, x has at t all and only the properties that y has at t.8

This is to say that a necessary condition of x’s identity with y is concurrent existence and possession of the very same properties at any time t. Synchronic identity thus entails numerical sameness of properties, but this requirement does not apply to diachronic identity.

Those sympathetic to Sider’s view will of course object to the Thomist’s defense of separate criteria for synchronic and diachronic cases. These objectors will simply respond: so much the worse for the

Thomistic view of substantial identity. If HE claims that its conception of substantial identity truly corresponds to numerical identity, the Thomist is simply mistaken.

The Thomist response to this further objection reveals a deep ideological rift between this view and

Sider’s. This division, which appears inescapable, concerns what identity is. Sider, on the one hand, insists that the conditions of identity are given by the principle of the Indiscernibility of Identicals.

HE, on the other hand, rejects this claim and points to pre-philosophical use of the concept of identity. In everyday thought and speech, it is normal to maintain that objects that have undergone

8 Aquinas (New York: Routledge, 2003), p. 45.

178 minor changes with respect to parts or properties are the same individuals. As Stump writes:

Now on a commonsensical view of change over time, change is a matter of one and the same thing’s having a property at one time which it lacks at another time. Medieval metaphysics, including Aquinas’s, begins with a commitment to this commonsense notion of change and then works to find an explanation of something’s remaining numerically one and the same through the change.9

To see the force of this point, consider that there is no worry that a man losing his hair is no longer the same man; there is merely the worry that the same man has less hair. It is only because pre- philosophical frameworks countenance substantial identity in the face of such changes that puzzles about identity can arise. When changes exceed the bounds of the ordinary, philosophical problems emerge, such as the puzzle of the Ship of Theseus or the question of whether an acorn is the same as an oak tree. The presupposition exposed by these puzzles, that numerical substantial identity is possible through accidental change, indicates that the pre-philosophical concept of substantial identity is not property-for-property sameness. Consequently, HE need not—and should not— accept Sider’s claim that substantial identity simply is sameness in every respect. The hylomorphic endurantist should instead point to pre-philosophical usage as evidence that he is talking about identity, and perdurantists such as Sider are discussing a concept that, though perhaps philosophically interesting, is not identity.

The advocate of HE should also note that Leibniz’s Law has no obvious claim to being a definition or a necessary consequence of identity simpliciter. Rather, it is a necessary consequence of identity at a given instant, that is, synchronic identity. One observes that the identity of O and P at any instant

9 Aquinas, pp. 44-45.

179 requires that O and P possess all the same properties. Leibniz’s Law is simply the codification of this pre-philosophical observation. This observation does not extend to diachronic phenomena, so the principle of the Indiscernibility of Identicals should not guide identity statements regarding these phenomena.

The preceding replies to Sider also serve to fend off a possible objection from a fellow Thomist. To begin his objection, the Thomist points out that the composite of form and matter is not in fact identical to the individual substance or supposit because the supposit includes the accidents and esse.

Thomas affirms this distinction explicitly in the Summa theologiae:

[I]n things composed of form and matter, the nature or essence is necessarily different from the supposit. For the notion of nature or essence includes everything that falls under the definition of the species...But the matter of the individual, along with all the individuating accidents, do not fall under the definition of the species.10

Embracing the Thomistic view, the objector claims that the individual substance at time t is not the same as the individual substance at t' if the two have different accidents—even if the form and matter are numerically the same. This conclusion appears to follow from the fact that a supposit includes accidents, which are not included in the essential principles. According to this understanding of Thomas’s metaphysics, then, an individual (supposit) at time t would not be the same as an individual (supposit) at t' if those individuals did not possess all the same accidents. In other words, one could not restrict individual identity (the identity of supposits) to the identity of

10 ST I, q. 3, a 3, co., Leon. 4.39. “In rebus compositis ex materia et forma, necesse est quod differant natura vel essentia et suppositum. Quia essentia vel natura comprehendit in se illa tantum quae cadunt in definitione specie… Sed materia individualis, cum accidentibus omnibus individuantibus ipsam, non cadit in definitione specie.”

180 essential principles.

From what has been said above, it should be clear that numerical identity for the Thomist is not a matter of identity with respect to every accident. This is true even though an individual at any instant is more than a mere compound of form and matter. The Thomist accepts the following claims:

1. An individual substance includes substantial form, matter, accidents, and esse.

2. At any instant, an individual substance is not identical to the composite of its substantial

form and matter taken alone.

3. A substance O is identical to a substance P iff O and P have the same substantial form and

continuous matter.

The objector suspects that (3) is inconsistent with (1) and (2). This objection arises from confusion about identity and the principles of identity. The objector is suggesting that the supposits must be identical to whatever accounts for their identity. Clearly, if the identical individuals do not share all the same accidents, it cannot be their accidents that account for their identity. If essential principles account for the identity of the individuals, he thinks, then the individuals must be identical to their essential principles. HE rejects this inference. The objects that are identical with one another are not therefore identical to their principles of identity. This is a critical distinction to bear in mind, for it is a defining aspect of HE. The principles of identity merely account for the numerical identity of a substance; they are not identical to that substance.

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The Problem of Temporary Intrinsics Neutralized If only for its notoriety, the problem of temporary intrinsics deserves a response from HE. The official HE position, alluded to in chapter 1, is that the problem is not a true problem at all. Rather, the problem arises from assumptions that the hylomorphic endurantist does not share. Nonetheless, the problem still poses an important question for endurantists: How is an object O wholly present at t and t' if it possesses at t a property that it lacks at t'? From what has been discussed already, it is clear that HE furnishes an answer: O is wholly present because it retains the same form and matter across those times. I will now elaborate on each these points.

To see that the problem of temporary intrinsics is a pseudo-problem for HE, recall that Lewis frames the problem in terms of the inconsistency of whole presence with a change of intrinsic properties. He claims that an object O cannot have a property F at t but lack F at t' while being wholly present. Why not? His most direct statement of the “problem” makes it difficult to find any legitimate reason for concern:

The principal and decisive objection against endurance, as an account of the persistence of ordinary things such as people or puddles, is the problem of temporary intrinsics. Persisting things change their intrinsic properties. For instance shape: when I sit, I have a bent shape; when I stand, I have a straightened shape. Both shapes are temporary intrinsic properties; I have them only some of the time. How is such change possible?11

From this one might construct a semantic problem along the lines raised by Merricks. That is, one

11 On the Plurality of Worlds, pp. 203-204.

182 might hold that for temporary intrinsic properties F and not-F, the propositions “O is F at t” and

“O is not-F at t'” generalize to “O is F” and “O is not-F.” The difficulty at hand would then be constructing a semantic solution, presumably some rationale that precludes the generalization.

However, there is not clearly an associated ontological problem.

To introduce an ontological puzzle where none is apparent, Lewis draws on his views about modality. He states,

Endurance through time is analogous to the alleged trans-world identity of common parts of overlapping worlds; perdurance through time is analogous to the `trans- world identity', if we may call it that, of a trans-world individual composed of distinct parts in non-overlapping worlds.12

This comparison is unsurprising: The discussion of endurance and perdurance, though widely cited in literature on identity, is in fact a digression in Lewis’s discussion of trans-world identity. Just prior to formulating the problem of temporary intrinsics, Lewis develops its modal sibling, the problem of accidental intrinsics. This puzzle emerges in the course of an attempt to explain the grounds for various true modal statements, such as “Hubert Humphrey could have won the 1968 presidential election.” Lewis entertains and rejects as an explanation the theory of “trans-world identity.” This theory is roughly that modal statements are true because individuals, such as Humphrey, exist both in our world, with its limited set of realized possibilities, and in other worlds, across the totality of which these same individuals realize all possibilities not realized in our world. There is a world in which Humphrey wins the election, another in which he has six fingers on his left hand, one in

12 On the Plurality of Worlds, p. 203.

183 which he is a concert bassoonist, and so on for every possibility concerning Humphrey.

Lewis commends the theory of trans-world identity for its directness and simplicity, but he claims that it creates an insoluble problem. Specifically, it cannot provide a satisfactory treatment of

“accidental intrinsics,” or intrinsic but changeable properties. He offers the example of having five fingers on one’s left hand: if Humphrey has five fingers but could have had six, the theory of trans- world identity holds that he has five fingers in this world but six fingers in another. This, however, is an outright contradiction because we are speaking of one and the same Humphrey rather than two distinct but related Humphreys or two parts of a greater Humphrey. There are a few possible solutions to this problem:13

1. Part of Humphrey (the part that exists in our world) is five-fingered, and another part (which

exists in another world) is six-fingered. Unfortunately, trans-world identity cannot adopt this

solution, for its central claim is that Humphrey exists wholly in any world where he exists; no

world contains only a part of the whole Humphrey.

2. Modal realism is false; one should treat possible (but not actual) truths about Humphrey as

sorts of false stories about him. This option also is not open to the proponent of trans-world

identity, who holds that possibly true statements about Humphrey in our world are actually

true in some other worlds.

3. Finally, treat intrinsic properties as relations to worlds. On this view, Humphrey bears the

13 On the Plurality of Worlds, p. 200.

184

five-fingered relation to this world and the six-fingered relation to other worlds. Lewis

rejects this option because it denies that seemingly intrinsic properties are intrinsic; they are

instead misconstrued as relations to worlds.

Lewis’s assessment of these options shows that his central objection to trans-world identity is the theory’s contention that individuals exist “wholly” in every world where they exist. The whole, selfsame Humphrey exists in our world and in various other worlds; thus the problem with his possessing incompatible intrinsic properties. If only part of him existed in our world and different parts existed in other worlds, the problem of accidental intrinsics would not arise. Lewis accordingly endorses a theory that offers something like a partitioning of individuals across worlds, but his views on modality do not further concern us here.14

The foregoing discussion may seem like an over-long foray into Lewisian modal theory, but it is necessary because the problem of temporary intrinsics simply transfers the problem of accidental intrinsics from the realm of modality to the realm of time. Lewis argues that, just as an individual cannot be wholly present in different worlds and possess incompatible intrinsic properties, no individual can possess incompatible properties at different times in a single world and be wholly present at those times. However, our ordinary discussion of change, in which an individual loses a property while seemingly remaining numerically the same individual, assumes that this is possible.

There are three ways of addressing this difficulty, which mirror the three solutions to the problem of

14 On the Plurality of Worlds, p. 202.

185 accidental intrinsics. First, one can claim that all intrinsic properties are relations to times so that there are no so such things as incompatible properties; all properties are differentiated by their times.

On this view, Samson is never long-haired simpliciter, but he is long-haired only in relation to time t or time t'. An alternative to this approach is to embrace presentism and denying that there are instants other than the present. Disdaining the first two views, however, Lewis turns to his preferred solution: the theory of temporal parts. Lewis explicitly connects this solution to his approach to the problem of accidental intrinsics: “Perdurance, which I favor for the temporal case, is closer to the counterpart theory which I favor for the modal case; the difference is that counterpart theory concentrates on the parts and ignores the transworld individual composed of them.”15

The problem Lewis has generated rests on premises that HE need not accept. The parallel between modal realism and time, which undergirds the problem, is mistaken. Although Lewis’s writings suggest that any difference in intrinsic properties will generate the problem of accidental intrinsics, this is not quite true. Consider again the case of Humphrey’s fingers. It is not in fact problematic to claim that he has five fingers in one world and six fingers in the other, for it is also possible to be five-fingered and six-fingered in the very same world.16 Suppose that Humphrey is born with six fingers on one hand and later has the extra digit amputated; let this be true in both worlds. It is still true that he has five fingers in one world and six in the other, but there is no incompatibility. There would only be incompatibility if the properties were temporally qualified to make them incompatible across worlds; for instance, if Humphrey never had more than five fingers in one world but sometimes had

15 On the Plurality of Worlds, p. 203. 16 This is not to beg the question of whether there is a problem of temporary intrinsics. The point here is only that some contradictory predications are not sufficient on their own to generate the problem of accidental intrinsics.

186 more than five in the other, or if he had no more than five fingers after age 10 in one world but not in the other, and so on. It is only these temporally qualified cases that matter because the properties in these cases are “timeless” properties; they are true of Humphrey at all times. It is problematic that

Humphrey both never has more than five fingers (in one world) and sometimes has more than five

(in another); instances such as this motivate Lewis to say that an individual cannot be wholly present in multiple worlds. The solution here is straightforward: reject modal realism, or at least Non-

Lewisian versions that espouse trans-world identity. More importantly, there can be a problem of temporary intrinsics only if there are similar incompatible temporally qualified properties in the temporal case. Lewis offers no reason to believe that there are such similar problem cases, but this subject deserves some brief consideration before we move to another puzzle about identity through time.

The troublesome premise that creates the problem of accidental intrinsics is that the selfsame individual can be wholly present in different worlds. Discarding this premise makes it possible to pursue one of the solutions suggested by Lewis. When Lewis proceeds to ask about temporary intrinsics “How is such change [of intrinsic properties] possible?” he assumes that whole presence across times is similarly troublesome. The nature of the trouble is unfortunately elusive. It cannot be an ontological difficulty about incompatible timeless properties, for there is only one world and one consistent set of temporally qualified properties in the temporal case. There are no difficulties about a man with at most five fingers on his hand in one world and at least six fingers on that hand in another. While it may be true at t that someone’s hand has at least six fingers and at t' this same hand has no more than five fingers, this change is unproblematic. No timeless truths arise from

187 these states of affairs, so there is no incompatibility.

If there is a bona fide ontological difficulty embedded in the problem of temporary intrinsics, it seems to be the puzzle of the Indiscernibility of Identicals, approached in a roundabout manner.

Lewis does not say this, and he may have thought he had developed a novel challenge to endurantism. Absent a true parallel between the modal case and the temporal case, however, Lewis’s problem seems to be one that has been raised and addressed already in this chapter: How is an individual the same whole at t and t' if it possesses incompatible properties at those times? The lengthy admonition to readers to bear in mind the appropriate notions of whole and part (often obscured by certain unnamed philosophers) supports this reading of Lewis.17

As I read Lewis, then, his question is how an object is wholly present at distinct times if it differs with respect to its intrinsic properties at those times. Setting aside Lewis’s presuppositions about modality and time, one can still find this question reasonable. If the whole of an object O is form and matter (on an Aristotelian view) along with esse (on a Thomistic view) and features or accidents, how can we say that two wholes are the same when they differ with respect to one or more of those constituents? It would seem more accurate to say that O is “partially present” at all the times that it exists.

17 On the Plurality of Worlds, p. 203.

188

Recall that the HE response concedes part of Lewis’s claim, but not all of it. If the whole that the perdurantist has in mind is an individual existing at a given instant, with all its ontological constituents at that moment, then no material object is wholly persistent through time. This is an obvious result of the fact that things change. However, if “whole presence” refers simply to a mode of existence across time that avoids temporal part theory, then HE provides a definition of this concept that should satisfy Lewis. On the HE view, every substance exists as a whole composed of essential parts and non-essential parts at every moment of its existence. In virtue of the sameness of its substantial form and the continuity of its matter, the substance remains numerically the same whole even though it changes with respect to its accidents and non-essential parts. This view clarifies how an object is the same even though it changes its properties.

Before proceeding to the next puzzle, a short word about an alternative solution is in order. Jeffrey

Brower has presented a version of his Aristotelian endurantism (reviewed in chapter 2), dubbed

“Thomistic endurantism,” as the Thomistic response to the problem of temporary intrinsics.18 This solution relies upon a putatively Aristotelian doctrine that Brower terms “numerical sameness without identity.”19 On this view, individuals, such as Socrates, are form-matter complexes that temporarily constitute larger wholes, such as musical Socrates and white Socrates, by acquiring such properties as being musical and being white. These larger wholes, termed “accidental unities,” are

18 Brower presents the solution in Aquinas’s Ontology of the Material World (Oxford: Oxford University Press, 2014), pp. 178-79. 19 Brower himself leaves doubt as to whether Aristotle or Thomas accepts this doctrine. He states, “Whether or not this understanding of the doctrine captures Aristotle’s own views, I shall assume in what follows that it is of at least broadly Aristotelian provenance”; Aquinas’s Ontology of the Material World, p. 94. About Thomas he remarks, “As far as I know, there are no texts in which Aquinas straightforwardly and unequivocally asserts the doctrine of numerical sameness without identity in precisely the form that I have presented it”; Aquinas’s Ontology of the Material World, p. 96.

189 the direct or immediate bearers of properties on Brower’s view. The underlying individuals, such as

Socrates, bear properties only derivatively. As a result, enduring individuals themselves never possess incompatible properties directly.20

Brower interprets the problem of temporary intrinsics to be essentially the same as the

Indiscernibility of Identicals, which it is not. Setting that concern aside, his solution is nonetheless problematic, as demonstrated in chapter 2. The primary objection to his view is that substantial individuals themselves, rather than accidental unities, possess properties directly. Musical Socrates is musical because Socrates is musical; seated Socrates is seated because Socrates has sat. Brower’s ontology reverses the order of dependence: Socrates is seated because seated Socrates is seated.

There is no need to accept this unfortunate consequence, so Brower’s theory should be rejected in favor of the view of whole presence articulated above.

The Problem of Material Constitution Solved The PMC encompasses a number of puzzles that raise a common problem: it appears possible for the same collection of constituents to compose simultaneously a) an object that necessarily bears relation R to its parts and b) an object that need not bear relation R to its parts. For our purposes, the PMC offers an occasion to distinguish the identity conditions of substances from the identity conditions of certain non-substances. The various permutations of the problem test assumptions about how these conditions may be the same or different. The competing intuitions that emerge in

20 Aquinas’s Ontology of the Material World, pp. 94-95.

190 reaction to the puzzles demand a response from any theory of identity over time.

To understand HE’s approach to the PMC, it is necessary to recall that the problem rests on five plausible but incompatible assumptions about composition and identity found in each puzzle:

1. There is an object of type F that is composed of certain parts, referred to as “the ps.”

2. Whenever the ps compose an F, they compose an object that essentially bears relation R to

its parts.

3. Nonetheless, if the ps compose an F, they also compose an object that can exist and not bear

relation R to its parts.

4. If the ps compose O and P, then O are P are identical.

5. If two objects are identical, then necessarily they are identical.21

Now, one could on principle reject one of these assumptions in all instances. One would then have a general solution to the PMC, an approach that neutralizes every instance of the problem. Some philosophers, for instance, reject (4) and embrace a theory of relative identity. This move allows one to avoid the contradiction that arises from certain transitive claims about identity in a PMC puzzle, where ordinarily the philosopher must accept that A=B and B=C implies A=C. When A=C proves to be a problematic statement, perhaps because A and C have incompatible properties, the advocate of relative identity can say that A is not absolutely identical to B, but only under a certain

21 Michael Rea, “The Problem of Material Constitution,” The Philosophical Review 104:4 (October 1995), pp. 527-28.

191 description.22 This strategy can be applied to any instance of the PMC, as can any other general solution, such as rejecting the claim that composition ever occurs. These blanket rejections of the assumptions underlying the PMC provide a way around all versions of the problem.

A partial solution, as the name suggests, addresses only some instances of the PMC. Unlike a general solution, a partial solution does not reject wholesale any of the general premises that generate the

PMC. Instead, partial solutions tend to question whether these premises hold for certain sets of cases. Van Inwagen and Merricks, for instance, deny the existence of many objects of ordinary discourse, including all artifacts.23 This position leads them to reject the first premise above in any puzzle case concerning artifacts. Although this approach dispatches a large number of PMC puzzles, van Inwagen and Merricks must provide another partial solution, distinct from the objection to artefactual existence, should they wish to solve every instance of the PMC.

Because HE does not reject any of the premises behind the PMC, the theory can offer only a set of partial solutions, which may or may not jointly address every instance of the PMC. Notably, HE’s approach to the problem depends on the nature of the objects and relations under discussion. What holds true for an organism, for example, may not hold true for an artifact. It is therefore in distinguishing between the classes of entities to which the PMC premises apply differently that HE

22 An example of this approach can be found in Peter Geach, Reference and Generality (Ithaca, NY: Cornell University Press, 1980), pp 215-218. 23 For van Inwagen, see Material Beings (Ithaca, NY: Cornell University Press, 1990). For Merricks, see Objects and Persons (Oxford: Clarendon Press, 2001).

192 devises its solutions to puzzle cases.

HE addresses most PMC cases through the use of distinctions between types of entities. One distinction concerns substances and aggregates.24 Thomas holds that aggregates are not substances, and these two kinds of object possess distinct kinds of unity. From this—and some further premises to be discussed shortly—it follows that aggregates and substances cannot be co-located. A related distinction differentiates between substances and non-substantial artifacts. Underwriting this second distinction is Thomas’s claim that most (though not all) artifacts are not substances, which I shall explain in more detail later.25 The substance-aggregate distinction is more foundational, so I turn to it first.

On Thomas’s view, any object made by aggregation or composition cannot be a substance. He makes this point in a passage from the Summa theologiae, where the topic under discussion is the ways in which certain beings can be one in some respect while being distinct in another respect:

Thus, a whole in the genus of substance, composed of its parts, whether integral or essential, is one simpliciter, for a whole is a being and substance simply, but the parts are beings and substances within the whole. Yet things that are different according to substance and one according to accident are different simply and one in a qualified sense, as many men are one people, and many stones are one heap. These are unities of composition or order.26

24 As will become clear below, Thomas distinguishes entities formed by mere aggregation from entities formed by composition. Despite the risk of causing confusion here, I follow standard usage in calling both types aggregates. 25 For a discussion of the exception to this claim, see Michael Rota, “Substance and Artifact in Thomas Aquinas,” History of Philosophy Quarterly 21:3 (July 2004), pp. 241-259. 26 ST I-II, q. 17, a. 4, co, Leon. 6.121. “Sicut totum in genere substantiae, compositum ex suis partibus vel integralibus vel essentialibus, est unum simpliciter, nam totum est ens et substantia simpliciter, partes vero sunt entia et substantiae in toto. Quae vero sunt diversa secundum substantiam, et unum secundum accidens, sunt diversa simpliciter, et unum

193

Here Thomas affirms that substances possess unity simpliciter, but collections possess a lesser, accidental sort of unity, a unity of composition or order. This passage explicitly states that aggregates such as heaps have a non-substantial sort of unity, and it is reasonable to infer that “compositions,” such as houses, also have a non-substantial unity (another text to be presented shortly will corroborate this inference). The crucial point is that Thomas distinguishes certain aggregates or collections of objects from substances. These non-substantial objects therefore do not have substantial forms and a fortiori cannot have the same identity conditions as substances.

A clearer picture of the difference between the identity conditions of substances and aggregates appears in Thomas’s commentary on the De Anima. Commenting on Aristotle’s discussion of nutrition, Thomas states that growing, and thus remaining identical through the addition of matter, is a process unique to living substances. He writes:

For instance, if some wood is newly set aflame, this new fire does not preserve the preexisting fire in another bundle of wood [to which the new wood was added], for the whole fire, which is formed from the collection of many flaming things, is not one thing simply, but it is one thing by aggregation, as a heap of stones is one. [...] In contrast, living bodies are truly nourished, for by food life is preserved in the very same part where it had been. Consequently, only living things actually grow, for every part of them is nourished and grows. This does not happen with lifeless things, which increase only by addition: their previously existing parts do not increase, but instead they are formed into a different, larger whole by the addition of another part.27

secundum quid, sicut multi homines sunt unus populus, et multi lapides sunt unus acervus; quae est unitas compositionis, aut ordinis.” 27 Sentencia De anima 2, Leon. 45.104-105: 143-157. “Puta, si aliquod lignum de novo ignitur, per hanc ignitionem non conservatur ignitio alterius ligni prius igniti: totus enim ignis qui est ex congregatione multorum ignitorum, non est unus

194

Here Thomas draws a contrast between the growth of a certain class of substances, namely living things, and the merely apparent growth of non-living substances. Living things, on the one hand, remain numerically the same when they acquire new matter, for the matter is integrated into the preexisting substance. Non-living substances, on the other hand, cannot increase while remaining numerically the same. The addition of one fire (a substance, on Thomas’s view) to another, for instance, creates a larger aggregate of two flames, not a single larger substance. As new parts are added to an aggregate, the aggregate does not remain numerically the same; instead, a new aggregate is formed. It will become clear shortly that the solutions to some puzzle cases turn on this critical distinction.

Thomas’s thoughts on aggregates govern his treatment of most artifacts. A passage from Book II of the Sentences Commentary is a useful starting point for exploring this approach. In this text, Thomas argues that the components of heavenly bodies in no way make up the substance of a human person. Underpinning his argument is a series of distinctions about how composition can happen:

For several bodies come to constitute a single body in only three ways: through simple aggregation, as when stones make a heap; through a composition that has a determinate and connected ordering of the parts, as when wood and stones make a house; and through mixing, when a mixed body is made from the elements. In none of these ways can some part of a heavenly body enter into composition with a human body: for, in the first two modes every part must be distinct in location from the others... [and] in the third mode there must be alteration of the components, for

simpliciter, sed videtur unus aggregatione, sicuti acervus lapidum est unus...Sed corpora animata vere nutriuntur, quia per alimentum conservatur vita in illa parte eadem, quae prius fuit. Et propter hoc etiam sola animata vere augentur, quia quaelibet pars eorum nutritur et augetur; quod non convenit rebus inanimatis, quae videntur per additionem crescere. Non enim crescit id quod prius fuit, sed ex additione alterius constituitur quoddam aliud totum maius.”

195

mixing is the union of altered things that are miscible.28

This passage distinguishes the formation of a heap, a process of “aggregation,” from the construction of a house, a process of “composition,” and the creation of a mixed body, a process of

“mixing.” (Recall that I am using the term ‘aggregate’ to refer to the products of composition as well as the products of aggregation). Although Thomas does not say so here, the process of mixing is necessary (but not sufficient) for the formation of a substance that is composed of more than one of the natural elements (fire, air, earth, and water according to medieval physics).

This background on the structure of aggregates sheds light on Thomas’s views about artifacts.

Thomas holds that—for the most part—artifacts are similar to aggregates (specifically, those formed by composition and not mere aggregation) in that they are not substances with respect to their forms, although they are substances with respect to their matter. By way of illustration, consider a lump of bronze that is shaped into a statue of Apollo. The statue, Thomas would say, is a substance in virtue of being a mass of bronze. However, its Apollonian shape is merely an accidental form, not a substantial form. Therefore, if the same lump is reshaped into a sword, the substance remains the same even though there is now a distinct artifact. Any accident, whether an arrangement or not, cannot be restored numerically the same once gone. Thomas makes this point clear when addressing

28 In II Sent., d. 17, q. 3, a. 1, co., ed. Mandonnet 2.435. “Quia quod plura corpora veniant ad constitutionem unius, hoc non potest esse nisi tribus modis: vel per simplicem aggregationem, sicut ex lapidibus fit acervus: vel per compositionem, quae est cum ordine partium determinato et ligamento sicut ex lignis et lapidibus fit domus: vel per mixtionem, sicut ex elementis efficitur mixtum. Nullo autem istorum modorum potest aliqua pars de natura caelestis corporis in compositionem humani corporis venire: quia in primis duobus modis oportet unamquamque partium esse distinctam secundum situm ab alia...in tertio autem modo oportet adesse alterationem componentium, quia mixtio est miscibilium alteratorum unio.”

196 the question of whether a statue once destroyed can be restored:

A statue can be considered in two ways: either with respect to what makes it a substance, or with respect to what makes it an artifact. The statue belongs to the genus of substance on account of its matter, so it remains the same insofar as it is a certain substance if it is remade from the same matter. However, it belongs to the genus of artifacts with respect to its form, which is an accident that departs when the statue is destroyed. In this case, the accident does not return numerically the same, nor can the statue be numerically the same [if destroyed and remade].29

Here Thomas distinguishes between the statue as a hunk of some material substance and as an arrangement of that substance. The substance, he says, is simply the hunk of underlying matter. This can survive changes to many of its accidents, including its shape or arrangement. In contrast, the arrangement itself cannot survive destruction or deformation. This follows from Thomas’s belief, mentioned in the previous chapter but merely implicit in the text above—that something cannot cease to exist altogether and return numerically the same. The crucial point is that artifacts, considered as artifacts, have different identity conditions from substances. When an artifact’s defining accidental characteristic, such as its shape or arrangement of parts, is destroyed, the artifact ceases to exist. In contrast, substances, and living substances in particular, can survive through many accidental changes because these changes do not interrupt the persistence of their substantial forms or the continuity of their matter.

With the differences in identity conditions for substances and non-substances in place, it is now

29 In IV Sent., d. 44, q. 1, a. 1, qc. 2, ad 4, ed. Vivès 299. “Ad quartum dicendum, quod statua dupliciter considerari potest; vel secundum quod est substantia quaedam, vel secundum quod est artificiale quoddam. Et quia in genere substantiae ponitur ratione suae materiae; ideo si consideretur secundum quod est substantia quaedam, est eadem numero statua quae ex eadem materia reparatur. Sed in genere artificialium ponitur secundum quod est forma, quae accidens quoddam est, et transit, statua destructa; et sic non redit idem numero, nec statua idem numero esse potest.”

197 possible to see how Thomas’s distinctions apply to PMC puzzle cases. One instance of the PMC, the

Debtor Paradox, offers an occasion to apply the distinction between the identity conditions of substances and the identity conditions of aggregates. This particular puzzle, of ancient pedigree,30 can be summarized simply: One individual, a borrower, receives a sum of money from a lender.

When the sum is due, the borrower objects that he does not owe the money. At the time of lending, the borrower claims, the person who incurred the debt was identical to a certain aggregate of matter.

Since that time, however, many additions have been made to that aggregate, and the alleged borrower of the present day is identical to a different aggregate of particles, not the original aggregate. Therefore, being a different man from the one who borrowed the money, he does not owe anything.

Christopher Brown, who has written extensively on the Thomistic approach to the PMC, outlines the assumptions of the paradox thus:31

1. The aggregate of the debtor’s particles at t+1 is identical to the debtor at t+1.

2. The debtor at t+1 is numerically identical to the debtor at t.

3. The debtor at t is numerically identical to the aggregate of his particles at t+1.

4. From (1)-(3), the aggregate at t+1 is numerically identical to the aggregate at t.

5. However, the aggregate at t+1 is not numerically identical to the aggregate at t.

As Brown notes, the Thomist dismisses claims (1) and (3). A living substance, such as a human, is

30 The first appearance of the puzzle is attributed to Epicharmus, per his words as recorded in DK 23 B 2. 31 Aquinas and the Ship of Theseus: Solving Puzzles about Material Objects (London and New York: Continuum, 2005), p. 152.

198 not identical to an aggregate of particles. As chapter 3 explained, a substance is a composite of substantial form and matter that includes esse and accidental features. Accordingly, the borrower could never be identical to only the aggregate of his particles. Furthermore, as discussed above, the identity conditions for a substance differ from the identity conditions for an aggregate. Substantial identity does not depend on the particle-for-particle persistence of matter, but the identity of an aggregate does. The outcome of these two positions is that there is no identity relation between the borrower and the aggregate of his particles. Consequently, a change in this aggregate does not affect the numerical identity of the borrower.

This response should be unsurprising. However, it raises a further question about the Thomistic view of composition. Because Thomas’s metaphysics denies that the aggregate and substance are identical, it must espouse one of two claims. First, Thomas could accept that wherever there is a material substance, there is a second, spatially coincident material object not identical to the substance, namely the aggregate of that substance’s particles. This would commit him to a doctrine of spatial coincidence without identity, which most philosophers reject. To avoid this conclusion, he could argue that there is no such object as the aggregate of a substance’s particles. This, however, is also a rare position in philosophy.

The response of HE is to reject the existence of an aggregate of a substance’s particles. Interestingly, the primary reason for this rejection is not opposition to the spatial co-location of objects. To be sure, Thomas does indicate that he would deny that such spatial collocation is possible: his view of individuation entails that a distinction of material substances implies a distinction of spatial

199 locations. For instance, in his Commentary on the De Trinitate of Boethius, Thomas affirms that

“numerical diversity arises from the same cause as that which necessitates the diversity of places for different bodies.”32 However, his explicit reason for denying the coincidence described above is his thoroughgoing rejection of the existence of aggregates within substances. Although Thomas believes that aggregates exist, he argues that they are never part of or coincident with an individual substance.

As noted above, an aggregate is a collection of individual substances, such as a mass of water molecules, a bouquet of flowers, or a human pyramid. These aggregates may be disorderly or well- organized, cohesive or scattered, but they are not substances. Conversely, a substance does not contain aggregates. The reason for this incompatibility turns on Thomas’s understanding of substantial unity and the role of substantial forms.

For Thomas, a substance is a single, unified object whose parts are not independent entities. That is, a substance is not a collection of preexisting parts; rather, all those parts come to be and have their being only as parts within the substance. The organizing and unifying principle of a substance is its substantial form. This form accounts both for the substance’s functioning as a whole and for the ordering of each part’s function to the function of the whole. He elaborates on this role of substantial form when explaining that the soul exists in every bodily part in SCG:

Thus the soul is the form of the entire body and likewise the form of the individual parts. If it were instead the form of the whole and not of the parts, it would not be the substantial form of the body, just as the form of a house, which is the form of a whole and not of the parts, is an accidental form. That the soul is the substantial form of the whole and the parts is evident from the fact that it determines the species of the parts and the whole. Accordingly, when the soul is gone, neither the

32 Super Boetium De Trinitate q. 4, a. 4, co. “Et sic patet quod ex eodem causatur diversitas secundum numerum, ex quo causatur necessitas diversitatis locorum in diversis corporibus.”

200

whole nor the parts persist under the same species, for the eye and flesh of a dead person bear their names only equivocally.33

In any substance, on Thomas’s view, there is a single substantial form for all the parts that determines their identities. The parts, therefore, are not a collection or organization of independent individuals but instead different parts of matter informed by one substantial form (and possibly by a variety of accidental forms). An aggregate, in contrast, is just such a collection or organization of independent individuals, as a house is a carefully ordered group of beams, boards, and other parts.

Consequently, though a substance has parts, these parts do not constitute an aggregate or anything other than the substance itself. HE’s response to many instances of the PMC is simply to observe this fact.

The principles just used to solve the Debtor Paradox can solve other instances of the PMC that involve substances. Take, for example, the puzzle of Tibbles, a cat who loses her tail.34 This situation generates a paradox if one believes that Tibbles is identical to the aggregate of her parts. Holding this belief means that a) Tibbles is initially identical to an aggregate including her tail and b) Tibbles is later identical to an aggregate that does not exclude her tail. Because the two aggregates are not identical to one another, it seems that one must hold that Tibbles does not remain numerically the same during the interval in which she loses her tail.

33 SCG II c. 72, Leon. 13.456-57. “Sic autem anima est forma totius corporis quod etiam est forma singularium partium. Si enim esset forma totius et non partium, non esset forma substantialis talis corporis: sicut forma domus, quae est forma totius et non singularium partium, est forma accidentalis. Quod autem sit forma substantialis totius et partium, patet per hoc quod ab ea sortitur speciem et totum et partes. Unde, ea abscedente, neque totum neque partes remanent eiusdem speciei: nam oculus mortui et caro eius non dicuntur nisi aequivoce.” 34 The best-known description of this puzzle appears in David Wiggins, “On Being in the Same Place at the Same Time,” Philosophical Review 77 (1968), pp. 90-95.

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Denying the existence of aggregates within substances, as Thomas does, solves the problem. If

Tibbles is never identical to any aggregate, then she cannot be identical to two different aggregates.

This is the route for the Thomist to take when confronted with instances of the PMC that pit the persistence of a substance against the destruction of a putative aggregate that is identified with the substance.

For all the elegance of HE’s solutions, there is an important objection to the theory that deserves consideration. One may think that denying the existence of aggregates within substances is too high a price to pay. Considering the Debtor Paradox, it may seem reasonable to believe that there is a collection of organs, cells, molecules, and so on within a human because those constituents can be removed from one individual and made to function in another. Furthermore, certain aggregates have causal properties; for instance, the water in one’s body contributes to one’s neutral buoyancy—the tendency to float in water without rising or sinking. One might therefore hold that the Thomistic view is simply mistaken about aggregates.

When weighing this objection, it is first necessary to distinguish between two types of parts. The first occurs only within the body of a certain species: a dog’s heart, a pig’s lungs, or a human’s hands.

Call these “species-specific parts.” The second type of parts appears in many species as a result of being ingested or otherwise integrated from the external environment: water, oxygen molecules, minerals, and the like. Call these “non-species-specific parts.” HE addresses the objection somewhat

202 differently for each kind of parts.

Turning to species-specific parts, recall that Thomas does not deny the existence of these parts of substances. A human body, for instance, does have a heart, white blood cells, and a host of proteins.

These parts possess a variety of features: shapes, weights, dispositions to act in certain ways, and so on. The Thomist accepts these facts; he further accepts that one may describe these facts in such a way as to give the impression that there are aggregates within a substance. For instance, one might say, “Proteins account for 20 percent of my body mass.” On the Thomist’s view, there is nothing false about this statement even though it may lead someone to believe that there is an aggregate of proteins within a substance. The Thomistic understanding of this statement, which precludes the collocation of the body and an aggregate, is that predications about bodily constituents are ultimately predications about the substance. Thus, a statement about water in the body is ultimately a statement about the body’s proteinaceous tissues. In this and all other predications about parts of a substance, the Thomist denies the existence of an aggregate by referring the properties of parts back to the body.

The response outlined above provides a promising start to a solution, but it is incomplete. The objector is apt to rejoin that the features of parts should not be referred back to the substance because the parts retain these features when removed from the substance. A heart, for instance, retains the capacity to pump blood if removed from the body by a skilled surgeon. It seems, then, that this and other features belong to the heart, and the case is analogous for other parts that can be explanted or transplanted.

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The Thomist reply here turns on the Aristotelian understanding of parthood for living things. A part of a living thing, the Aristotelian holds, derives its identity from its function within the living thing.

A heart, for instance, is the part of the body that initiates circulation of the blood. This part may be structured so as to complete this function effectively, but it is the function, not the structure, that defines the part. As Thomas puts it:

After the soul’s departure, flesh, bones, hands, and similar parts bear their names only in an equivocal sense since none of these parts retains its proper operation, which results from the species [of the substance].35

A species-specific bodily part, then, is whatever functions in a certain role within the body. This is true whether the part is natural or synthetic, like an artificial heart. In fact, the very existence of artificial organs lends support to this idea, for these devices are clearly organs only when functioning within a body. The dependence of the part on the body for its identity is thus explained by the dependence of the part on the body for its function: a bodily part functions properly as a result of the action of the whole organism, not by its own power. This is manifestly the case with the heart, which relies on numerous bodily systems, most notably the autonomic nervous system, to function as a circulator of blood. Given their dependence on bodies, bodily parts exist only within living bodies and owe their existence to these bodies. When removed from a living body, a part is no longer a part but an organized collection of elements—an aggregate—that might once again function as a part within a body (it is a potential bodily organ or tissue). It is therefore incorrect to say that bodily parts possess features outside the body, for these parts do not exist outside the body. It is

35 SCG II, c. 57, Leon. 13.407. “[N]am caro et os et manus et huiusmodi partes post abscessum animae non dicuntur nisi aequivoce; cum nulli harum partium propria operatio adsit, quae speciem consequitur.”

204 likewise wrong to conclude that organs, tissue, or cells compose aggregates inside the body simply because they do so outside the body.

The situation is different with non-species-specific parts. Unlike species-specific parts, these constituents exist as substances or aggregates prior to entering the organism. Water, for instance, is clearly a molecule (and plausibly a substance) before it is ingested. It exhibits its characteristic functions just as well outside an organism’s body as within. Consequently, there is no prima facie reason to claim that water and other non-species-specific parts derive their identity and function from an organism’s substantial form.

The independent substantiality of these parts poses a problem, for they seem to be distinct substances that are nonetheless integrated into other substances, namely organisms. The existence of multiple substances within a single organism is problematic for Thomas, who subscribes to the following principle about substantial forms: Any substance has just one substantial form, so it cannot have other substances (and thus other forms) as parts. For instance, in the Summa theologiae he writes, “A single thing has one substantial being. Now a substantial form confers substantial being.

Therefore, there is just one substantial form for a single thing.”36 This rejection of multiple substantial forms in one substance means that organisms contain no substances, not even molecules such as water, lipids, and proteins, which are components of the body and seem to be substances

36 ST I, q. 76, a. 4, s.c., Leon. 5.223. “[U]nius rei est unum esse substantiale. Sed forma substantialis dat esse substantiale. Ergo unius rei est una tantum forma substantialis.”

205 outside the body. This is paradoxical and demands an explanation.

Thomas addresses this concern partially (but only partially, as we shall see shortly) when he discusses how the most basic substances—“elements,” in Aristotelian terminology—may become parts of more complex substances or “mixed bodies.” Although today’s science no longer recognizes the

Aristotelian elements (water, air, earth, and fire) as such, the philosophical problem remains the same now as it was in Thomas’s time: in what state do the most basic independently existing entities, whatever these may be, persist when they become parts of more complex substances? Rejecting the answer that the elements remain as substances, Thomas must accept either that 1) they vanish altogether or 2) they remain, but not as substances.

Thomas recognizes that complex substances (which he calls “mixed bodies”) incorporate the characteristics of simpler constituents, so the first option is wrong. The moistness, heat, and other such properties of complex objects clearly arise from the properties of basic constituents. Therefore, these constituents persist somehow in more complex substances. This persistence amounts, in

Thomas’s view, to the preservation of the constituents’ powers—but not their substantial forms— within complex substances. He writes,

In this way, then, when the extremes of the elementary qualities are lessened, a certain middle quality is constituted from these. This quality is the proper quality of a mixed body, and it differs in various mixed bodies according to the different proportions of mixing. This quality is also the proper disposition for the form of a mixed body, just as a simple quality is the disposition for the form of a simple body...

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A quality of a simple body is something different from its substantial form. Nonetheless, a quality acts by the power of the substantial form. Otherwise, heat [from a substance] would only make things hot, but a substantial form would not be brought into act by [the heat’s] action because nothing acts outside the limits set by its species. Therefore, the powers of the substantial forms of simple constituents are preserved in mixed bodies.37

Thomas’s view is that the distinctive qualities of elemental substances are blended and tempered when these substances combine to form a more complex substance. The resulting “mean” quality emerges from the qualities of the elemental substances; however, neither the substantial forms nor the original qualities of these substances remain. There is nonetheless a prospect of recovering these forms because the qualities of elemental substances, when isolated, provide the necessary and sufficient foundation or “disposition” for the elemental substantial forms. This enables Thomas to say that elemental qualities actually persist in complex substances and elemental substantial forms persist “virtually.”

Thomas’s solution may work given an Aristotelian conception of the elements, but it is not quite sufficient in light of modern chemistry. To preserve the phenomena known to the scientists of his day, Thomas needs only to account for the presence of certain elemental qualities, such as lightness and heat, in complex substances. There is little reason for him to believe that the elements themselves persist when incorporated into larger substances.38 The case is different today, for we can

37 De mixtione elementorum, Leon. 43.156:130-147. “Sic igitur remissis excellentiis qualitatum elementarium, constituitur ex hiis quedam qualitas media que est propria qualitas corporis mixti, differens tamen in diuersis secundum diuersam mixtionis proportionem; et hec quidem qualitas est propria dispositio ad formam corporis mixti, sicut qualitas simplex ad formam corporis simplicis... Qualitas autem simplicis corporis est quidem aliud a forma substantiali ipsius, agit tamen in uirtute forme substantialis; alioquin calor calefaceret tantum, non autem per eius actionem forma substantialis educeretur in actum, cum nichil agat ultra suam speciem. Sic igitur uirtutes formarum substantialium simplicium corporum in corporibus mixtis saluantur.” 38 One may nonetheless wonder whether perspiration and similar macrophysical occurrences would constitute evidence

207 track individual compounds that organism ingest. Water, proteins, fats, and a host of substances become part of life processes before being broken down or transmuted into other compounds. This means that there is a need to provide an account of how these compounds, which are plausibly substances, persist in the body without preserving the substantial mode of existence that they enjoy outside the body.

Building on Thomas’s thought, Patrick Toner articulates the beginnings of such an account. Like

Thomas, Toner denies that substances have substances as parts, and he adds some persuasive arguments for this view to the standard Thomistic repertoire. Because the focus of this discussion is not the justification for this view of substantial unity but the neutralization of an objection, I will pass over Toner’s arguments (but I recommend them to the reader on their own merits).39 The part of his account that is relevant in the present context is his conception of nominal presence. This type of presence contrasts with what one might call the substantial (or, on Michael Rea’s terminology, “classificatory”) presence of an object, the “normal” existence of a substance outside another, more complex substance.40 When an object such as a water molecule exists on its own, not as a part of something else, it is (plausibly) substantially present; it is a substance. When a water molecule is caught up in the life processes of an organism, however, it is no longer substantially

that water persists in the body in Thomas’s eyes. 39 See “Emergent Substance,” Philosophical Studies 141:3 (December 2008), pp. 281-97. Toner argues that a Thomistic account of substance can address both the Vagueness Argument for unrestricted composition and Overdetermination Argument. The first of these is the position—rejected by Toner—that any two objects compose a third because denying this claim (restricting composition) would mean that it is indeterminate whether composition occurs in some cases. The second argument contends that certain macrophysical objects do not exist because, if they did, both these objects and their parts would be causally responsible for—and thus overdetermine—certain events. As Toner sees it, the Thomistic theory of substance allows one to resist the conclusions of both arguments. 40 Toner adopts the idea of nominal presence from Rea’s “Constitution and Kind Membership,” Philosophical Studies 97:2 (January 2000), pp. 169-93.

208 present, yet it retains many of the qualities it possessed outside the organism. Toner refers to this continuity of qualitative features as the nominal presence of a water molecule in an organism: there is no longer a substance that is a water molecule, but a portion of the organism now exhibits many of the properties of a freestanding water molecule. These properties no longer belong to a molecule; instead, they are possessed by the organism.41 This outline of nominal presence aligns closely with

Thomas’s view of the persistence of elements in complex substances: the elements do not endure as substances, but their qualities remain.

Toner’s greatest contribution to a solution, and the area in which he goes beyond Thomas, is coupling nominal presence with a theory of existential statements. For it to be true that x’s exist,

Toner says, it must be true that “the property x is instantiated.”42 In both cases of substantial and nominal presence, the same property x is instantiated, so in both cases x’s exist. In the one instance, it is a substance that instantiates the property; in the other, part of a substance instantiates the property. However, there is a crucial difference: in the case of the substance, the question “What is it?” is best answered by “It is an x.” In the case of a spatial part of a substance, the same question is not best answered in this way. With substances, the relevant causal powers and properties belong to the substance; with parts, the causal powers and properties belong to the substance in which the part exists. By way of illustration, this means that a certain freestanding substance can be a water molecule by instantiating the property is a water molecule, while a (non-substantial) part of an organism may instantiate this same property without being the same sort of thing, namely a water molecule, as

41 “Emergent Substance,” p. 289. 42 “Emergent Substance,” p. 289.

209 the molecule. When the freestanding molecule enters an organism, a substance ceases to exist, but part of the organism starts to exemplify the property is a water molecule. On this view, it is perfectly correct to speak of the number of water molecules in a body and to discuss the collective mass or charge of those molecules. All the properties mentioned or implied in these statements, however, belong to the organism itself, not to a substance or aggregate of substances collocated with the organism. This theory of nominal presence thus preserves the appearances while avoiding the difficulties created by positing the existence of aggregates within substances.

Taking Stock HE has the resources to address the full array of standard problems about diachronic identity. The theory’s solutions to these problems are at times surprising, as exemplified by the rejection of a diachronic version of the Principle of the Indiscernibility of Identicals. Nonetheless, these solutions are founded on the framework of Thomistic metaphysics, so they are consequences of Thomas’s thought—unforeseen, perhaps, but not ad hoc. Moreover, as consequences of a metaphysical theory, they belong to a framework motivated by concerns independent of diachronic identity.

There are, then, reasons to accept the principles of Thomistic ontology apart from its success in solving puzzles about diachronic identity.

Just as importantly, the review of HE’s solutions showcases the theory’s defining features. HE offers a definition of whole presence that exposes the false assumptions of the problem of temporary intrinsics. The theory’s treatment of synchronic and diachronic identity as one phenomenon with different manifestations emerges in HE’s response to Leibniz’s Law. And teasing out answers to the

210 various instances of the Problem of Material Constitution offers an opportunity to understand how

HE differentiates the identity conditions for substances, aggregates, and accidental forms. In the course of these investigations it has become apparent that HE is a distinctive theory: it can provide new and thoughtful answers to classic and contemporary problems because it draws on a metaphysical system that modern philosophy has yet to explore fully.

While it would be an exaggeration to say that this chapter has simply read the solutions to problems about identity over time out of Thomas’s texts, it would not be far from the truth. It requires only modest extensions and interpretations of his writings to arrive at solutions to the puzzles discussed in this chapter. It would be comforting if this pattern held for all problems concerning diachronic identity. The puzzles about self-change discussed in chapter 1, however, do not admit of such straightforward treatment. The next chapter explains how HE must add substantially to the principles of St. Thomas when addressing the problems of self-change.

CHAPTER 5: IDENTITY THROUGH SELF-CHANGE—HE ON EMBRYONIC DEVELOPMENT

The basic outline of hylomorphic endurantism is now complete. Chapter 4 showed that HE offers the most compelling endurantist solutions to the chief concerns about identity over time that appear in contemporary philosophical literature. Nonetheless, there are difficult questions about diachronic identity that HE does not clearly address. Among these are the scenarios of the self-change of organisms introduced in chapter 1. Consider, for instance, the development of a caterpillar into a butterfly: is the caterpillar numerically the same individual as the butterfly? On the one hand, it appears that there is a continuous, intrinsically driven process of development within a single entity, as opposed to a fusion or fission involving multiple entities. Therefore, there seems to be one continuous existence and one individual. On the other hand, it seems that being a caterpillar and being a butterfly are essentially different: a caterpillar does not exhibit the defining characteristics of a butterfly (flying, feeding through a proboscis, and so on), nor does a butterfly display the characteristics of a butterfly. If a caterpillar and a butterfly are essentially different, then they must also be numerically different.

There are numerous similar examples involving organismic self-change. The maturation of almost every complex organism raises the question of whether a relatively undifferentiated embryo is the same individual as its adult successor, which possesses a host of well-defined structures and capacities to act. In each case, there is an apparently continuous, internally directed process that points to the existence of a single persisting individual. Yet the juvenile also lacks the defining features of the adult, so the two appear to be distinct individuals. This paradox, which I have couched in non-philosophical terms, begs for philosophical elucidation.

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The diachronic identity of developing organisms has received attention from philosophers, but interest is skewed heavily toward the human case. This follows from the relevance of human identity to debated areas within bioethics, including abortion and human stem cell research. The same concerns seldom arise with non-human animals, so the resulting philosophical investigation is species-specific. Moreover, the investigation of ontology in this literature tends to be limited, as the authors often are aiming to settle practical concerns rather than to open theoretical inquiries.1

Fortunately for the present inquiry, Thomas himself takes an interest in biological development, if only in the human case, and its bearing on identity, mainly in two contexts. First, he considers human development when addressing the question, how many souls (and thus substantial forms) does a human have? He also does so when investigating the origin of the human body and soul, specifically whether these are created by God or generated from parental matter.

Before searching Thomas’s writings for a theory of development, however, it is first necessary to say a brief word about what such a theory should offer. Any investigation of identity through development must address three points. First, in order to overcome the limits of most accounts of

1 A sample of this literature includes Phillip Montague, “Stem Cell Research and the Problem of Embryonic Identity,” Journal of Ethics 15.4 (2011): pp. 307-319; Jeff McMahan, “Killing Embryos for Stem Cell Research,” Metaphilosophy 38 (2007): pp.170–189; A.A. Howsepian, “Four Queries Concerning the Metaphysics of Early Human Embryogenesis,” Journal of Medicine and Philosophy 33.2 (2008): pp. 140-157; and Mark T. Brown, “The Potential of the Human Embryo,” Journal of Medicine and Philosophy 32.6 (2007): pp. 585 – 618. Works with more (though still somewhat limited) discussions of development in an ontological framework include Lynne Rudder Baker, Persons and Bodies (Cambridge: Cambridge University Press, 2000) and Eric Olson, “Was I Ever a Fetus?” Philosophy and Phenomenological Research 57.1 (1997): pp. 95- 110.

213 development, it must offer a characterization of development in metaphysical terms. Second, the theory must investigate the causes of development: what accounts for the initiation, continuation, and completion of development? What explains why developmental processes follow one course rather than another? Finally, the theory should explain how these causes preserve or destroy the numerical unity of the developing individual. HE holds that numerical identity rests on the continuity of matter and the preservation of numerically the same substantial form. The primary claim under investigation is that some phases of development do not preserve the organism’s substantial form. Accordingly, we must determine how the causes of development relate to the substantial form, and whether the behaviors of organisms at different phases of development are signs of a discontinuity of substantial form.

Thomas’s Theory of Embryological Development A Thomist will naturally look to Thomas’s writings for a theory of development. Even a casual reading of the literature on Thomas’s views of development shows that he has a relatively consistent view of development, or at least of human development. In its rough outline, his theory is that humans and other animals come to be only after a series of generations from simpler life forms. The offspring of the parents is at first a vegetative being, which grows without exercising or even possessing powers of sensation. The father’s semen, which supposedly persists after conception, then forms the vegetative embryo into a creature capable of sensation—a new substance altogether, which possesses a distinct substantial form. Finally, in the case of humans, the semen further forms the sensitive embryo into a being with the organs necessary to support a rational substantial form.

This substantial form, the human soul, is infused by God, and a new substance—now a human one—is formed.

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We will delve further into the details of this account shortly. At present, it suffices to note that it is unsatisfactory for two reasons. First, Thomas relies on a thoroughly debunked embryology. He had no notion of genetic material or of the fusion of parental chromosomes during fertilization.

Consequently, he was unaware of the manner in which genes orchestrate a series of developmental events. His analysis of development is thus an account of an imaginary process, wholly different from what unfolds in the early stages of life. Second and more fundamentally, a true notion of development seems to be absent from Thomas’s writings. He recognizes a series of generations, each giving rise to a new substance. He also acknowledges a distinct phenomenon of growth, which is merely the increase in the dimensions of a living body. Although one might reasonably hold that parts of development are mere generation or growth, this view is manifestly incomplete.

Development encompasses the formation of new tissues and the acquisition of new functions within a single, persisting individual.

The point of reviewing Thomas’s theory, then, is not to defend it. Rather, it is to pinpoint the places in which his theory fails and to devise a theory that addresses those weaknesses. Thus, this chapter will not be an extension or interpretation of Thomas’s thought in the way the previous chapter was.

Nonetheless, studying Thomas’s view on development will also enable us to preserve any elements of his thought that may contribute to a better theory.

As we begin to study Thomas’s writings on development, two points bear mention. First, he

215 addresses the human case almost exclusively and refers to the genesis of other animals only in the context of considering human development. Second, the Sentences Commentary is not the best source for his thoughts on this subject. Although he does discuss human generation in a few places in the Commentary, he provides a more comprehensive and unified discussion in Summa contra

Gentiles (SCG) II chapters 83-89. Therefore, the exposition here will draw primarily on the latter work.

In SCG, the discussion of human embryonic development emerges in the course of investigations about the human soul. When taking up the topic of development in chapter 83, Thomas has already established that the intellectual soul is the substantial form of the body (chapter 57), that each individual has only one soul (chapter 58), and that the human soul—unlike the body— is incorruptible (chapter 79). From this last point it is clear that the conditions of existence for the soul differ from those for the body. Does this mean then that the soul exists prior to the body? Thomas argues not, and this argument leads him into a discussion of the origin of the human soul.

Because Thomas’s treatment of development is situated within investigations about the rational soul, it focuses exclusively on humans. The souls—that is, the substantial forms—of non-human animals, he contends, are not intellectual or incorruptible.2 Therefore, they exist only in conjunction with a body and do not raise the philosophical problems raised by human souls. Nonetheless, much of what Thomas says about human souls implies similarities and differences with non-human souls.

2 See, for example, SCG II, c. 82.

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Since this work concerns the diachronic identity of living things in general, the similarities will be our main interest.

When discussing when and how souls come into existence, Thomas considers a few options. One option that deserves only brief mention is the possibility that souls exist before their bodies, either eternally or temporarily. The debate about this proposition is something of an intramural dispute between Christian Platonists and Christian Aristotelians, which does not concern us here.3 Thomas offers a host of arguments to show that a) there is no good reason to suppose that souls existed prior to bodies and b) there are many reasons to believe that souls come into being simultaneously with bodies. Here he introduces the argument that the soul does not exist before the body because it is natural for substantial forms to be united to their “proper matter” and unnatural for them to be separated.4 Thomas does not elaborate here on what sort of matter is proper to the soul and what is not, but this proves to be a critical distinction for later discussions.

After Thomas dismisses the view that souls exist before bodies, he turns first in chapter 85 to the claim that the soul arises from God’s substance–which we will pass over here—and then to more

Aristotelian options in chapter 86. The generic Aristotelian view is that the male semen (believed to be inanimate excess matter in the father’s body) acts to form the female menstrual blood—the matter of generation—into an embryo. Importantly, the semen has no intrinsic power to act on the menstrual blood, but the father’s soul confers this power—the “formative power”—on the semen.

3 The Christian Platonist Thomas has in mind is Origen, who is rather far from mainstream Christianity on this point. 4 SCG II, c.83, Leon. 13.520. “Unicuique formae naturale est propriae materiae uniri.”

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The power serves not only to form the embryo but also, once the embryo has been formed, to further shape it into a new being endowed with more complex organs.5

Although the initial action of the semen on the menstrual blood produces an embryo, this embryo is not an individual of the parents’ species. Rather, the embryo is a vegetative being, regardless of whether the parents are humans or non-human animals.6 Thomas contends that in this early stage the embryo is not of the parents’ species and instead must pass through a series of corruptions and generations to become human.7 This difference in kind is evident in the embryo’s lack of the functions definitive of the species and the organs necessary for performing these functions. 8

5 Thomas’s account of the process appears in SCG II, c. 89. 6 SCG II, c. 89, n. 11. 7 The most relevant passage is Quaestiones de Potentia (QDP) q. 3, a. 9, ad 9, ed. Marietti 2.68. “In generatione autem animalis apparent diversae formae substantiales, cum primo appareat sperma, et postea sanguis, et sic deinceps quousque sit forma hominis vel animalis. Et sic oportet quod huiusmodi generatio non sit simplex, sed continens in se plures generationes et corruptiones.” See also SCG II, c. 89, n. 11, and ST I, q. 118, a. 2, ad 2. 8 Thomas makes this point most clearly in QDP q. 3, a. 11, co. This passage speaks generally of the difference between vegetative, sensible, and rational souls, and the context (human development) makes clear that Thomas has in mind the succession of souls in the human embryo. Note especially: “Ab hac autem generalitate formarum oportet excludere animam rationalem. Ipsa enim est substantia per se subsistens; unde esse suum non consistit tantum in hoc quod est materiae uniri; alias separari non posset: quod falsum esse etiam eius operatio ostendit, quae est animae secundum se ipsam absque corporis communione. Nec potest aliter operari quam sit…Neutrum autem horum de anima sensibili vel vegetabili dici potest. Esse autem huiusmodi animarum non potest consistere nisi in unione ad corpus: quod eorum operationes ostendunt; quae sine organo corporali esse non possunt: unde nec esse earum est eis absolute sine dependentia ad corpus…Huiusmodi etiam animae ordinem principiorum naturalium non excedunt. Et hoc patet earum operationes considerantibus. Nam secundum ordinem naturarum sunt etiam ordines actionum. Invenimus autem quasdam formas quae se ulterius non extendunt quam ad id quod per principia materialia fieri potest; sicut formae elementares et mixtorum corporum, quae non agunt ultra actionem calidi et frigidi; unde sunt penitus materiae immersae. Anima vero vegetabilis, licet non agat nisi mediantibus qualitatibus praedictis, attingit tamen operatio eius ad aliquid in quod qualitates praedictae se non extendunt, videlicet ad producendum carnem et os, et ad praefigendum terminum augmento, et ad huiusmodi; unde et adhuc retinetur infra ordinem materialium principiorum, licet non quantum formae praemissae. Anima vero sensibilis non agit per virtutem calidi et frigidi de necessitate, ut patet in actione visus et imaginationis et huiusmodi; quamvis ad huiusmodi operationes requiratur determinatum temperamentum calidi et frigidi ad constitutionem organorum, sine quibus actiones praedictae non fiunt.” SCG II, c. 86 makes similar points but does not explicitly mention the relationship between form and function. For more on the relationship between kind membership and functions or operations, including further texts from Thomas, see the discussion later in this chapter.

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Thomas also denies that the embryo plays any active role in the acquisition of these definitive functions. The embryonic soul is responsible for nutrition and growth and, when it is a sensitive animal soul, for sensation as well. However, embryonic growth is merely quantitative, an expansion in extent or an increase in mass. The embryo does not initiate or oversee the differentiation of its own structures and functions. Instead, the formative power of the semen directs this process.9

This characterization of the embryo’s role has three far-reaching consequences. First, because the embryo is responsible for some vital functions, Thomas grants that it has a soul. By definition, a soul is a principle of vital operations, so any being carrying out vital operations must be ensouled. An embryo therefore is a living substance, an individual organism, by virtue of having a soul, and not an inanimate mass or a part of another substance. The first consequence, then, is a positive recognition of the embryo’s ontological status.

In contrast, the second consequence is negative. Because the embryo does not control its own development, the developmental process cannot be considered a process of self-change. Functional, structural development takes its direction from outside principles. The embryonic individual is the passive subject of this process, and developmental activity is not an operation of the embryo but simply a series of changes effected in the embryo.

9 SCG II, c. 89, n. 8.

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Finally, and most importantly at present, the embryo’s gradual acquisition of more complex organs and functions amounts to a series of transitions from one kind of being to another. The embryo is first equipped with merely vegetative powers—nutrition and growth—so it is a plant-like creature with a vegetative soul, not an animal or a human. Next, upon acquiring the powers of sensation and motion, the embryo has an animal—but still not rational or human—soul. It is no longer a plant-like being, but not yet a human either. Only upon acquiring the defining characteristics of a human—a soul with a capacity for reason and a body suited to this soul—does the embryo become human.

Notably, Thomas denies that the pre-rational embryo is specifically a plant or a non-human animal.

He prefers to say that human embryos lack any species at all, and that they are “on their way to a species.”10 However, it is evident that the embryo is different in kind from a rationally ensouled human.

The description above makes clear that Thomas’s characterization of the embryo’s species revolves around the activities in which it engages. Why is this? Thomas holds that we do not have direct, immediate knowledge of essences. Instead, it is possible to ascertain the species of a given individual only through observation of traits or activities that are signs of the specific essence.11 The most important of these signs is engagement in the activity that is unique to a particular species. Each kind of being, Thomas claims, has a proper operation, an activity that is in some sense possible for all

10 SCG II, c. 89, Leon. 13.542. “Nec est inconveniens si aliquid intermediorum generatur et statim postmodum interrumpitur: quia intermedia non habent speciem completam, sed sunt ut in via ad speciem.” 11 See, e.g., Sentencia De Anima I, Leon. 45.7:254-56. “Sed quia principia essentialia rerum sunt nobis ignota, ideo oportet quod utamur differentiis accidentalibus in designatione essentialium.”

220 members of the species and only for members of that species. In the case of humans, Thomas states, this operation is the intellectual act of understanding:

It is possible to show that [the soul is the form of the body] from the nature of the human species. For the nature of anything is made manifest through its operation. Now the proper operation of man, insofar as he is man, is to understand, for in this way he goes beyond all brute animals...Consequently, man derives his species in virtue of the principle of this operation. But anything derives its species from its form. It thus stands to reason that the intellectual principle is the form of man. 12

Humans, Thomas states, are set apart from animals by engagement in intellectual activity. This distinctive activity points to a unique species, and thus a unique principle of the species, or substantial form. Accordingly, for Thomas this rule holds generally: where there is a distinctive type of activity unique to a group of individuals, there is an underlying substantial form that is unique to that group.

Thomas’s view of activities explains why he regards the vegetative embryo, the sensitive embryo, and the rational embryo as distinct individuals that belong to different species. According to the biological opinions on which Thomas relied, the vegetative embryo does not and cannot engage in movement or sensation. Thus, it cannot be an animal, much less a human. It does not exhibit the activities characteristic of any animal species; it simply grows like a plant. Similarly, the sensitive embryo cannot be human because it cannot engage in rational activity. Where there is no possibility

12 ST I, q. 76, a. 1, co., Leon. 5.209. “Potest etiam idem manifestari ex ratione speciei humanae. Natura enim uniuscuiusque rei ex eius operatione ostenditur. Propria autem operatio hominis, inquantum est homo, est intelligere, per hanc enim omnia animalia transcendit...Oportet ergo quod homo secundum illud speciem sortiatur, quod est huius operationis principium. Sortitur autem unumquodque speciem per propriam formam. Relinquitur ergo quod intellectivum principium sit propria hominis forma.”

221 of engaging in the proper operation of a species, there is no possibility of belonging to that species.

What, then, about an embryo with a rational soul? Does Thomas hold that there is evidence that it engages in rational activity? This question touches on an important nuance in Thomas’s view. He acknowledges the evidence that infants do not engage in intellectual activity, which indicates that embryos and fetuses do not engage in this activity, either. Given this conclusion, Thomas cannot consistently hold that infants and embryos do not perform acts of understanding while accepting that they are human. He must somehow modify or reject one of these views. Indeed, he does just this by rejecting engagement in the proper operation as a criterion for kind membership. In the place of engaging in the activity, Thomas substitutes the capacity to engage in the proper operation. For instance, with humans the capacity to understand dictates kind membership. Thomas applies this to the case of an infant in an interesting way:

A person is said to be capable of acting in one way before he has the nature by which he acts, and capable in another way after he already has that nature, but is accidentally prevented from acting... Now, a child can understand only potentially, not in the sense that he has does not have an intellectual nature already, but in the sense that he faces an impediment to understanding: he is hindered from understanding “by the variety of movements in him,” as is said in Physics VII. Therefore, he is not deemed to be capable of understanding because the possible intellect, which is the principle of understanding, can be united to him. Rather, the possible intellect is already united to him and is hindered in its proper action. Thus, upon the removal of the obstacle, the child will understand immediately.13

13 SCG II, c. 60, Leon. 13.421. “Aliter dicitur aliquis potens operari antequam habeat naturam qua operetur, et aliter postquam iam habet naturam sed impeditur per accidens ab operando... Puer autem est in potentia intelligens non quasi nondum habens naturam intelligendi, sed habens impedimentum ut non intelligat: impeditur enim ab intelligendo propter multimodos motus in ipso existentes, ut dicitur in VII physicorum. Non igitur propter hoc dicitur potens intelligere quia intellectus possibilis, qui est intelligendi principium, potest continuari sibi: sed quia iam est continuatus et impeditur ab actione propria; unde, impedimento remoto, statim intelligit.” The context for this remark is a refutation of Averroes’ claim that there is a single, separate possible intellect that furnishes all humans with the power of understanding. Thus the language of “uniting” the possible intellect and the individual.

222

This passage suggests that Thomas would assign a human nature to infants and young children even though they do not engage in acts of understanding. The reason for viewing these children this way is that they could engage in acts of understanding if they did not face certain transient physical impediments (identified in the Summa theologiae as excessive moistness of the brain14). They possess the power to engage in distinctly human acts, and that qualifies them as human. It is worth noting that in an extended discussion that encompasses the passage quoted above, Thomas explicitly says that a child in utero is specifically human despite not engaging in intellectual acts.15 This statement seems to apply the same counterfactual reasoning to children prior to birth: just like infants, they are human because they possess the potentiality to engage in intellectual acts.

As with all the principles enunciated above, the positing of the capacity for the proper operation as a criterion for kind membership does not apply only to humans. Shifting the criterion to capability or capacity raises an important question: what is it to have a capacity for a proper operation? What distinguishes the proto-human from the actual human, the proto-canine from the actual dog?

Turning from operations to capacities directs our attention from substantial form, the principle of proper operation, to matter. Every proper operation of an organism presupposes the adequate development and function of certain bodily structures. For instance, an orb weaver spider cannot engage in web-spinning (supposing this is its proper operation) without organs that support this

14 ST I, q. 101, a. 2, co., Leon. 5.447. “Vires autem sensitivae sunt virtutes quaedam corporalium organorum, et ideo, impeditis earum organis, necesse est quod earum actus impediantur, et per consequens rationis usus. In pueris autem est impedimentum harum virium, propter nimiam humiditatem cerebri. Et ideo in eis non est perfectus usus rationis, sicut nec aliorum membrorum.” 15 SCG II, c. 59, Leon. 13.416: “Sed puer, etiam antequam ex utero egrediatur, est in specie humana: in quo tamen nondum sunt phantasmata, quae sint intelligibilia actu.”

223 activity—legs, spinnerets, and so on. In the same way, all other organisms rely on the integrity of their bodily structures and functions to support their proper operations.

Thomas is clear that this requirement applies in the case of humans.16 When discussing the one-to- one correspondence of human bodies and souls in SCG, he writes, “Form and matter must always be reciprocally proportioned and naturally ‘fitted’ to one another, so to speak, for the proper act comes to be in the proper matter.”17 The point here is that activity that is unique to a particular form—and thus to a particular kind—presupposes a unique sort of matter. To be able to engage in a proper operation, then, an individual must have a certain kind of matter.

Thomas makes the correspondence between matter and capacity for a proper operation more explicit later in the same discussion of soul-body unity in SCG. In an argument against the view that the human soul preexists the body, he observes that a human needs the senses and thus the body to understand, even though understanding is an immaterial act. He writes,

Nature lacks nothing for the performance of its proper operation. It gives organs fit for sensation and motion to animals with souls capable of sensation and movement. Likewise, there would be no human soul without the necessary support of the senses. As we have seen, however, the senses do not function without bodily organs. Therefore, the soul was not made without bodily organs.18

16 This may appear surprising because Thomas holds that understanding is not the act of any organ. See below for further discussion of this point. 17 SCG II, c. 80, Leon. 13.505. “Formam igitur et materiam semper oportet esse ad invicem proportionata et quasi naturaliter coaptata: quia proprius actus in propria materia fit.” 18 SCG II, c. 83, Leon. 13.522. “Natura autem nulli deficit in necessariis ad propriam operationem explendam, sicut animalibus habentibus animam sensitivam et motivam, dat convenientia organa sensus et motus: non fuisset anima humana sine necessariis adminiculis sensuum instituta. Sensus autem non operantur sine organis corporeis, ut ex dictis patet. Non igitur fuit instituta anima sine organis corporeis.”

224

Thomas’s point is that every nature, that is, every kind, needs certain organs to be capable of performing its proper operation. This is true for all material substances and for humans as well.

Matter—here the organs—supplies the potency for the acts characteristic of a kind. Although the substantial form is the principle of the proper operation, there is no potency for this operation without the right kind of matter.

These passages establish that in Thomas’s view for any individual to be of kind F, it must possess the proper matter of kind F. Such matter is defined as the matter needed to enable the proper operation of that kind. Although this is rather abstract, Thomas provides a more concrete characterization of proper matter for humans. In the discussion of the origin of the human soul in

SCG, he argues against the preexistence of a human soul in the father’s semen by adverting to the type of matter required by a soul. Thomas states,

To understand, the soul needs powers for preparing phantasms so that they are made actually intelligible. These are the cogitative power and memory, which, since they are the acts of certain bodily organs through which they operate, cannot remain after [the corruption of the] body.19

This argument builds on Thomas’s earlier characterization of human intellectual cognition. Thomas believes that intellectual cognition is not carried out by any particular organ, but it does make use of products of the operations of certain organs, namely the cogitative power and memory. Without the

19 SCG II, c. 80, Leon. 13.505. “Indiget etiam anima ad intelligendum virtutibus praeparantibus phantasmata ad hoc quod fiant intelligibilia actu, scilicet virtute cogitativa et memorativa: de quibus constat quod, cum sint actus quorundam organorum corporis per quae operantur, quod non possunt remanere post corpus.”

225 preparatory work of these organs, the intellect could not perform acts of understanding. Therefore, the proper matter of a human being includes these organs, at the very least.

Even with this concrete description, there is some ambiguity in Thomas’s thought. He never says that an organism’s body must be structured such that it is capable of engaging in proper operations immediately. One could then hold that the presence of nascent, partially formed organs is sufficient for an individual to belong to the kind. However, Thomas does not admit this possibility anywhere.

As mentioned above, he admits that children may be rational without being able to engage in thought immediately and he makes a similar observation about mentally handicapped and insane persons. When discussing whether the latter kinds of individuals can be baptized, Thomas writes,

There is a distinction to be observed regarding the mentally handicapped and insane. For some individuals are born in these states and never have lucid intervals—in them the use of reason never appears. In such cases, it seems that the same judgment about administering baptism holds as with children, who are baptized in the faith of the Church, as stated above. But other individuals who lack reason have fallen into that state after previously being of sound mind. And in these cases we determine [to baptize or not] based on the state of their wills when they were of sound mind.20

In effect, Thomas is saying that we should treat cases of insanity or mental disability as the results of a physical impediment. He confirms this diagnosis in his response to an objection, which notes that human mental incapacity arises from a physical impediment, but the irrationality of brute animals results from the absence of a rational soul. Thomas’s approach to the distinction between congenital

20 ST III, q. 68, a. 12, co, Leon. 12.105. “Respondeo dicendum quod circa amentes et furiosos est distinguendum. Quidam enim sunt a nativitate tales, nulla habentes lucida intervalla, in quibus etiam nullus usus rationis apparet. Et de talibus, quantum ad Baptismi susceptionem, videtur esse idem iudicium et de pueris, qui baptizantur in fide Ecclesiae, ut supra dictum est. Alii vero sunt amentes qui ex sana mente quam habuerunt prius, in amentiam inciderunt. Et tales sunt iudicandi secundum voluntatem quam habuerunt dum sanae mentis existerent.”

226 irrationality and acquired irrationality in this passage is noteworthy. He compares the former to the irrationality (or proto-rationality) of infancy. Looking at the question with the aim of understanding

Thomas’s views on development, this seems surprising; it is acquired irrationality—not congenital irrationality—that may be transient like a child’s lack of reason. However, for Thomas’s purpose, which is pastoral, the comparison works: In both infancy and cases of congenital rationality there is no possibility of determining whether the person ever wished to be baptized. Because of this pastoral focus, the nature of the underlying defect is not clearly addressed. Does either congenital or acquired irrationality result from an “impediment” different from juvenile irrationality? If so, do these impediments reveal anything further about the physical condition that is sufficient for membership in the human species? Thomas’s writings unfortunately do not provide an answer.

Thomas’s View of Development in Relation to Diachronic Identity It is now time to take stock of the implications of Thomas’s embryology for diachronic identity. The first consequence is quite clear: Thomas’s reasoning leads to the conclusion that every organism that develops vital organs must proceed from being a member of one kind to being a member of another kind. For sake of clarity, we may term the initial kind(s) the “embryonic species” and final kind the

“mature species.” On Thomas’s view, all mature species possess organs that are necessary for the proper operation of that species. If these organs must be developed, then in the embryonic species there is no capacity—not even an impeded capacity—to engage in that operation. Accordingly, members of the embryonic species lack the capacity necessary to be members of the mature species, so there must be a change in species during embryonic development.

227

This discontinuity in species implies that the embryo and the mature individual are not numerically the same. Substantial form determines an individual’s species or kind, so, on Thomas’s view, the embryo and mature individual, which are of two distinct species, cannot possess numerically the same substantial form. Because numerical identity requires identity of substantial form, the individual embryo is not numerically identical to any individual of the mature species. In other words, there is not diachronic identity throughout the course of the development of animals (and perhaps other organisms as well). There is instead a succession of individuals who grow, die, and give rise to more complex individuals of different species. Of course, there is diachronic identity when organisms grow, but as noted above, mere growth is not the same as development in the sense currently under consideration.

It is important to observe that the discontinuity in identity does not arise from changes to the matter. To be sure, the putative presence of differently structured underlying matter (i.e., different organs) leads Thomas to claim that the substantial forms must be different in various phases of development. However, it is not the difference in matter itself that violates the criteria for diachronic numerical identity. In fact, materially, there appear to be no barriers to continuity. Recall that the material criterion for diachronic identity is continuity of matter through time. This criterion is satisfied throughout development (as Thomas understands it). The formative power first operates on the semen and menstrual blood to form a vegetative embryo; the power then forms this embryo into an animal; and, lastly, it develops the animal embryo’s organs to the point at which they can support an externally infused rational soul. Throughout this process, there is a transfer of matter from one substance to the next. It is for this reason that Thomas has to confront difficulties about

228 whether the matter of semen is restored to the father or his child at the resurrection.21

My understanding of Thomas on this point differs from that of Fabrizio Amerini, who has written extensively on Thomas’s embryology. Amerini argues that the matter of an embryo and the matter of a human being cannot be the same on the basis of a text from Thomas’s commentary on

Aristotle’s Metaphysics. Amerini summarizes the text as follows:

Thomas explains four cases in which A and B are per se identical or the same: (1) if the matter of A is numerically identical to the matter of B; (2) if the matter of A is specifically identical to the matter of B; (3) if there is a substantial continuity between A and B; (4) if A and B share a single and indivisible definition.22

In the passage Amerini cites (Exp. Met., V, l. 11, nn. 911-912), Thomas is explaining Aristotle’s classification of the ways in which things are said to be essentially the same. These five ways ultimately belong to two classifications, because being essentially the same resolves into being essentially one, on Aristotle’s view, and there are just two ways of being essentially one. The first classification includes things that have the same matter, whether numerically the same or specifically the same. The second includes things that are one in substance, either by continuity (part of the same quantity) or by definition (sharing the same nature). The synopsis from Amerini quoted above aptly summarizes four of the five types of essential sameness; he sets aside the fifth type of sameness, absolute identity in every respect, as clearly inapplicable for an embryo and a mature

21 SCG IV, c. 81, n. 13. See also In IV Sent., d. 44, q. 1, a. 2, qc. 4, ad 5. 22 Fabrizio Amerini, Aquinas on the Beginning and End of Human Life, trans. Mark Henninger (Boston: Harvard University Press, 2013), p. 112.

229 human.23

According to Amerini, we can rule out the possibility of numerical material identity (the first option) because “an embryo and a human being do not have exactly the same quantity of matter, that is, the same individual matter with the same extension.”24 He buttresses this claim with the observation that

Thomas argues against the numerical identity of parents and children by pointing to the non-identity of their matter. Amerini’s argument is that numerical material identity means particle-for-particle material identity, which everyone (Thomas included) agrees does not obtain between an embryo and a more mature human being. In support of this observation, Amerini cites one of the texts from

Book IV of the Sentences Commentary that I have used as a foundation for my interpretation of

Thomas (this is d. 44, q.1, a. 1, qc. 2, ad 1). As Amerini’s use of this text shows, his view opposes mine not only on the identity of matter in the embryo and adult, but on Thomas’s general understanding of the identity of matter.

Turning to the Sentences text, at first glance it seems that Amerini has a point. The passage that he cites responds to an objection that runs thus:

It seems that the same man [who died] will not rise again. As the philosopher says in Book II of On Generation and Corruption, anything that has a species subject to the motion of corruption will not return numerically the same. But human substance in its present state is that sort of thing. Therefore, after the transformation that is death it is not possible to return numerically the same.25

23 Aquinas on the Beginning and End of Human Life, p. 113. 24 Aquinas on the Beginning and End of Human Life, p. 113. 25 In IV Sent., d. 44, q.1, a. 1, qc. 2, arg. 1, ed. Vivès 295. “Videtur quod non sit idem numero homo qui resurget. Sicut

230

The objector is citing Aristotle to the effect that nothing that is corrupted can rise the same in number; the same individual cannot exist twice. Thomas rejoins that the pre-mortem and post- resurrection human is the same because its essential principles are not destroyed as the principles of other organisms are: “Rather, it should be said that the forms of other generable and corruptible things are not self-subsisting, so that they remain after the corruption of the composite, as the rational soul does.”26

Now, the main thrust of this rejoinder is not what interests Amerini; it is instead a remark at the end of the response that seems to serve his purpose. As Thomas concludes his reply, he states, “Nor is man restored numerically the same through natural generation. For the body of a generated man is not made from the entire matter of the generating man; whence the body is different in number, and thus so are the soul and the whole man.”27 This claim appears to mean the following: a parent and child are not the same because there is a partial difference in their matter, which is in itself a sufficient barrier to numerical identity. It may seem that this statement precludes identity between other entities that share their matter only partially, such as a vegetative embryo and an animal embryo arising from the same vegetative embryo. Amerini takes Thomas’s argument to have just this implication; the condition giving rise to the numerical distinction between parent and child is

enim dicit philosophus, 2 de generatione, quaecumque habent speciem corruptibilem motam, non reiteratur eadem numero. Sed talis est substantia hominis secundum praesentem statum. Ergo post mutationem mortis non potest reiterari idem numero.” 26 In IV Sent., d. 44, q.1, a. 1, qc. 2, ad 1, ed. Vivès 298. “Vel dicendum, quod aliorum generabilium et corruptibilium forma non est per se subsistens, ut post compositi corruptionem manere valeat, sicut est de anima rationali.” 27 In IV Sent., d. 44, q.1, a. 1, qc. 2, ad 1, ed. Vivès 298. “Sed tamen nec etiam homo per generationem naturalem reiteratur idem numero: quia corpus generati hominis non fit ex tota materia generantis; unde est corpus diversum in numero, et per consequens anima, et totus homo.”

231 the same condition that underlies the numerical distinction between the vegetative embryo and the animal embryo.28 However, it is important to keep in mind that Thomas is not concerned with the latter distinction here, so there is no indication in his text that he would draw the same conclusion as

Amerini.

An important oversight undermines Amerini’s claim. Specifically, he relies on an observation about sexual reproduction to make a claim about embryonic development. However, the two processes differ in numerous ways. The most salient in this instance is the following: In sexual reproduction, the new being arises from some matter detached from the father and mother, whereas in embryonic development the putative new embryo arises immediately from the matter of the allegedly prior embryo. Consequently, there are two important distinctions between the two scenarios. First, in sexual reproduction there is a synchronic distinction of matter—the parents are constituted by matter X and Y at the same moment the embryo is constituted by matter Z. Accordingly, the difference in identities arises from a synchronic distinction of matter rather than a diachronic discontinuity. The same cannot be said of embryonic development, during which the different embryos exist only sequentially, so there is no synchronic non-identity. The search for non-identity then turns to the diachronic contrast, but here there is a second difference. Because the later embryo arises directly from the totality of the earlier embryo, there is no distinction of matter between the two. Everything from the first embryo remains in the second. Further, even assuming the loss or addition of a few particles, this would not violate Thomas’s view of material continuity if (contra

Thomas) the later and earlier embryos had numerically the same form. There is, then, no reason to

28 Aquinas on the Beginning and End of Human Life, p. 113.

232 doubt that there is continuity of matter across the phases of embryonic development.

There is no discontinuity of matter in embryological development—at least not the sort of discontinuity that would prove an obstacle to identity in embryonic development. It is evident, then

(pace Amerini), that the discontinuity of form underlies Thomas’s views about non-identity in embryonic development. However, this discontinuity points us back to the complementarity of form and matter. The Thomistic view hinges on the claim that an embryo or juvenile, to be identical with a mature individual, must have numerically the same form as the mature individual. To do so, the juvenile must stand in a certain sort of potentiality to the proper operation of the mature individual.

The individual with adequate potentiality must possess the bodily structures needed for the proper operation, but not necessarily in their unimpeded state. Thus, the right sort of body (matter) is needed, but the requisite state of this body and its potentiality is only vaguely sketched.

To illustrate the vagueness in Thomas’s view, one need only look to the conflict among modern commentators. Pasnau, for instance, states that, according to Thomas, “we can say in at least rough terms when the human soul is infused: it is infused at that point when the fetus is sufficiently developed, in its brain and sensory systems, to support the soul’s intellectual operations.”29 Pasnau further explains that on Thomas’s view a fetus becomes human when it has the “capacity in hand for rationality,” when it can immediately engage in conceptual thought.30 Generalizing from the human

29 Robert Pasnau, Thomas Aquinas on Human Nature: A Philosophical Study of Summa Theologiae, 1a 75-89, (Port Chester, United Kingdom: Cambridge University Press, 2001), p. 111. In support of this view, Pasnau cites SCG II.89. 30 Thomas Aquinas on Human Nature, pp. 118-19. Pasnau attributes to Thomas the view that “a late term fetus is already in engaged in conceptual thought” though “Aquinas is never explicit on this point.” He also writes that Thomas is very

233 case to the more general case of organisms, we can formulate the requirement thus:

First Act Criterion (FAC): An organism belongs to kind F iff it possesses the material

structures required to perform the proper operation of kind F immediately.

Amerini adopts an interpretation similar to Pasnau’s, but with one further nuance. Discussing the conditions for being a human, Amerini writes,

The sufficient condition required for being able to speak of the embryo’s rational ensoulment is not given (1) by the possibility of possessing the capacity to reason, nor (2) by the possession of the capacity to actually reason, but (3) by the actual possession of the capacity to reason.31

The phrasing (admittedly a translation from Italian) is perhaps confusing. The phrase “ragionare in atto,” translated as “to actually reason,” could be rendered as “to engage in acts of reason,” with the implication that the capacity can be exercised immediately. In addition, the third condition translates more literally to “the possession of the capacity to be able to reason.”32

From this it appears that Amerini sees three types of capacity or potentiality where other writers see

generous in acknowledging the capacity for immediate thought in dubious cases (see Thomas Aquinas on Human Nature, p. 120); this view indicates that, on Pasnau’s reading, the ability to exercise the capacity immediately is essential. Otherwise, Pasnau would appear to be a proponent of a weaker reading of Thomas, WFAC, discussed below. 31 Aquinas on the Beginning and End of Human Life, p. 193. 32 The original Italian for conditions (2) and (3) is “né dal possesso della capacità di ragionare in atto, ma dal possesso della capacità di poter ragionare.” Fabrizio Amerini, Tommaso d’Aquino Origine e fine della vita umana (Pisa, Italy: Edizione ETS, 2009), p. 222.

234 two. First, there is the potentiality to possess, at some point in the future, the capacity to reason.

This potentiality, which is a potentiality to be in a state of first act (a state of having a capacity to act), Amerini rejects as insufficient for kind membership. Second, there is an unimpeded state of first act (“the capacity to actually reason”), which Amerini considers too high a bar for kind membership.

This condition, which requires any human to be able to engage in acts of reason immediately, is too stringent on Amerini’s view because it would preclude newborn infants, sleepers, and intoxicated individuals from being human (Thomas counts all these groups as human). Finally, there is the state of first act simpliciter (unimpeded or impeded), or the ability to engage in acts of reason, but with the proviso that the exercise of this ability may be impeded at present.33 Amerini believes this condition to be the one endorsed by Thomas, and in support of this interpretation he notes Thomas’s willingness to categorize newborns as fully human even though they cannot exercise their capacity for reason.34 Newborns are (evidently) human, but it is also evident that they do not engage in rational activity, so they must have a temporarily unactualizable capacity to reason. Once again generalizing this position to all organisms, we arrive at the following principle:

Weak First Act Criterion (WFAC): An organism belongs to kind F iff either 1) it satisfies

FAC or 2) it could satisfy FAC after the removal of a remediable impediment.

Amerini further weakens this criterion by suggesting that an embryo or mature human with an

33 Amerini does not use the term “first act” in this context, but he later introduces it (p. 200) as equivalent to “the possession of rational ensoulment” (for humans) and distinct from “the actual functioning of that ensoulment,” which is termed “second act.” 34 Aquinas on the Beginning and End of Human Life, p. 193.

235 irreversible, intrinsic impediment to reasoning (e.g., an irreparably damaged or missing organ) might still be deemed rational by Thomas.35 Amerini admits that this interpretation is “purely conjectural”; if it is correct, it would yield yet a different requirement for kind membership:

Counterfactual First Act Criterion (CFAC): An organism belongs to kind F iff either 1) it

satisfies FAC or 2) it would satisfy FAC in the absence of any irreversible impediments to

that performance and any irremediable hindrances to its development.

Haldane and Lee interpret Thomas’s thoughts on potentiality quite differently from Pasnau and

Amerini. They posit two possible and mutually exclusive requirements for membership in the human kind, which I have altered slightly to make the requirements applicable for all biological kinds:

P. 1) [FAC] what is necessary for [kind membership] is the presence of the actual organs, sufficiently developed to support the operations proper to that species; ... P. 2) [Epigenetic Primordia of First Act Criterion (EPFAC)]36 what is necessary for [kind membership] is the material organization sufficient for the development of those organs, in other words, the epigenetic primordia of the organs that support the operations proper to the species.37

The first criterion is the authors’ restatement of Pasnau’s criterion, which they reject. According to

35 Aquinas on the Beginning and End of Human Life, p. 197. 36 This is my acronym. 37 John Haldane and Patrick Lee, “Aquinas on Human Ensoulment, Abortion and the Value of Life,” Philosophy 78, April 2003, p. 268.

236 them, Thomas never asserts a requirement identical or similar to FAC (P.1). They further contend that Thomas probably held the Epigenetic Primordia of First Act Criterion (my terminology) because he believed that children were rationally ensouled before birth; however, he would not have held that these children were able to engage in intellectual activities. In other words, Thomas held

(or should have held) EPFAC because he extended kind membership to children who lacked fully developed organs. Notably, this reading overlooks Thomas’s belief that young children have an extrinsic, transient impediment to reason in their otherwise mature brains. I will set aside this interpretive issue for the time being and simply note that Haldane and Lee endorse EPFAC as the right reading of Thomas on kind membership.

Two problems prevent a definitive statement of Thomas’s position on potentiality. The first is textual. Beyond telling the reader that the body must be equipped with the right organs, Thomas does not specify the requisite condition of those organs for kind membership. How inchoate these organs may be within any particular kind is open to debate. A possible explanation for this first difficulty is the second problem: Thomas has a crude understanding of biological development in general, so many distinctions that would interest us simply are not present in his work. It is difficult to see how Thomas could endorse a view such as EPFAC, for instance, when he has no concept analogous to “the epigenetic primordia” of organs in the first place. Because the notion of intrinsically guided development is foreign to him, he never addresses the status of an embryo with partially formed organs. His thoughts on the rationality of children, the insane, and mentally handicapped are suggestive, but they too are marred by attention to transient exogenous defects, such as excessive motion and moisture in the brain, rather than endogenous defects, such as

237 malformed organs. While today’s philosophers can develop finer gradations of potentiality by making reference to the contemporary understanding of biological development, Thomas lacks that resource.

Thomas’s views of development are decidedly problematic for their biological inaccuracy and metaphysical unclarity. Setting his presuppositions and reasoning aside, he could still be correct that identity is discontinuous throughout development. Indeed, some contemporary philosophers accept this view of discontinuity for reasons similar in nature to Thomas’s, even if the arguments differ in their biological details. Peter van Inwagen, for instance, argues that a zygote is not numerically identical with an adult human because a zygote is essentially a single cell while an adult human is not.

Furthermore, the two cells that arise from the zygote’s division do not compose anything; they are

(for reasons that van Inwagen does not make entirely clear) simply two organisms that adhere to one another.38 Much like Thomas’s argument against diachronic identity throughout development, van

Inwagen’s position rests on supposed essential differences that arise as an embryo develops.

Like van Inwagen, Norman Ford argues on the basis of embryological data that the early embryo is not numerically identical with the later human individual, which on his view begins its life around 15 days after conception. He advances several arguments for this position, one of which concerns essential differences between the early embryo and the later individual. In Ford’s view, a living individual “of its own power from within itself, actively strives to be self-maintaining, self-

38 Material Beings (Ithaca, NY: Cornell University Press, 1990), pp. 152-53.

238 developing and functioning for its own welfare.”39 This is effectively Ford’s definition of living, though he does not say so outright. The processes of life in many organisms, Ford observes, result in part from the expression of the organism’s genome. Without genetic expression, the processes characteristic of each biological species would not take place. Because this expression does not and cannot occur in the early embryo, the embryo is not engaged in the life processes of any of those species, and it is essentially different from the individuals of those species.40

As van Inwagen and Ford show, it is still prima facie plausible to arrive at conclusions about identity through development similar to Thomas’s. Whether those conclusions can withstand serious scrutiny remains to be determined.

Objections to the Thomistic View and Similar Viewpoints The unsettled question of Thomas’s view of the potentiality of the embryo takes us from discussing the implications of his thought to the tenability of his position. As noted previously, there is one obvious reason that we should reject his view: his faulty biology. In animal reproduction, the semen does not persist as an active force “shaping” the embryo into a full-fledged member of the species.

Nor does the menstrual blood serve as the matter for the embryo. The very notion of an

39 See Norman Ford, When Did I Begin? (New York: Cambridge University Press, 1988), pp. 92, 118. 40 When Did I Begin? p. 118. The argument presented above is my interpretation of Ford’s thought. It is difficult to discern the structure of the argument he wishes to make in the passage where he states, “The human individual that is ontologically identical with the future adult could hardly be said to exist before the embryonic genome, including the paternal genes, is switched on.” My assumption is that Ford believes that some genomic expression is necessary for kind membership, but he never says this plainly. For a view that is similar to Ford’s, though it places the emergence of a human individual at 50 hours after fertilization, see Beverly Whelton, “Human Nature, Substantial Change, and Modern Science:Rethinking When a New Human Life Begins,” Proceedings of the American Catholic Philosophical Association 72 (1999), pp. 305-313.

239 extrinsically guided developmental process is incorrect. There are, indeed, extrinsic factors from the mother’s body and from the broader environment that influence development, but its basic course is determined by intrinsic genetic material.

Of all the biological errors in Thomas’s view, the most important is the claim that an external agent, namely the semen, guides the development of organs and functions of the embryo. A contemporary text on developmental biology clearly attributes the formation of organs to the cells of the embryo:

“Once the three germ layers are established, the [embryonic] cells interact with one another and rearrange themselves to produce tissues and organs.”41 Later processes of development that generate the organs of the mature organism, such as metamorphosis, are likewise internally initiated and controlled:

During metamorphosis, developmental processes are reactivated by specific hormones, and the entire organism changes to prepare itself for its new mode of existence. These changes are not solely ones of form. In amphibian tadpoles, metamorphosis causes the developmental maturation of liver enzymes, hemoglobin, and eye pigments, as well as the remodeling of the nervous, digestive, and reproductive systems. Thus, metamorphosis is often a time of dramatic developmental change affecting the entire organism.42

External modulation of these processes can occur. For instance, differences in the seasons influence whether newly developing aphids are asexually reproducing females or females who reproduce sexually.43 In every instance, however, it is the expression of embryonic genes that determines the

41 S.F. Gilbert, “The Circle of Life: The Stages of Animal Development,” Developmental Biology, 6th ed. (Sunderland, MA: Sinauer Associates, 2000). Available online at: https://www.ncbi.nlm.nih.gov/books/NBK9981/. 42 S.F. Gilbert, “Metamorphosis: The Hormonal Reactivation of Development,” Developmental Biology, 6th ed. (Sunderland, MA: Sinauer Associates, 2000). Available online at: https://www.ncbi.nlm.nih.gov/books/NBK9986/. 43 S.F. Gilbert, “Environmental Regulation of Normal DevelopmentDevelopmental Biology, 6th ed. (Sunderland, MA:

240 structure and function of the organism’s parts, not the working of an outside agent. External factors may influence whether or not the expression of certain genes takes place, but these factors cannot specify the result of these expressions. What an organism is and becomes, then, is intrinsically determined.

To say that organismic development is fundamentally intrinsic is to say that self-change is at work.

Self-change, as described in chapter 1, is causation in which an active potency within an individual— a power to φ—activates a passive potency—a power to be φ-ed. In development, powers that cause growth and differentiation actualize structures that grow and differentiate. Both the causative principles and the affected principles exist within the same developing organism. For example, in amphibian metamorphosis thyroid hormones promote the growth, differentiation, and degeneration of various physical structures.44 Both the causative agent—the hormones—and the affected structures are parts of the individual amphibian.

Once development is recognized as an instance of self-change, the question of numerical identity through development becomes a question about identity through self-change. The question now under consideration is this: Can an organism cause itself to become another kind of organism? As noted previously, it is a change in kind—and therefore substantial form—that must underlie any hypothesized breach in numerical identity during development. There is no difficulty with material continuity throughout the developmental process. The inquiry thus turns to an organism’s ability to

Sinauer Associates, 2000). Available online at: https://www.ncbi.nlm.nih.gov/books/NBK9981/. 44 Gilbert, “Metamorphosis.”

241 alter its own substantial form.

Substantial self-change is not possible on the weak conception of self-change that Thomas accepts.

Recall that in weak self-change a substance S causes some alteration in itself in follows: a part of S that has an active potency (a potency to φ) actualizes the passive potency (a potency to be φ-ed) of a different part. For instance, a part with the power to heat generates heat in another part with a capacity to be made hot. This understanding of self-change is inconsistent with substantial change, which is not the actualization of the passive potency of some part of a substance. Substantial change is the formation of a new individual in place of one or more individuals that pass out of existence.

Those former individuals are not actualized or altered in any fashion; they simply cease to be.

Substantial change is thus a change from one whole into a different whole, not a change within a given part, as self-change is.

The refutation of substantial self-change given above may seem incomplete. One might wonder if a substantial change could supervene on a self-change: could the change in a single part amount to a change from a substance of one kind to a substance of another kind? To apply this line of thinking to Thomas's embryology, perhaps the self-caused modification of a single organ in a vegetative embryo is enough to yield a capacity for sensation and thus a substance with a new, sensitive mode of existence. Why not admit possibilities of this sort?

To see why, consider the difference between accidental change and substantial change. In an accidental change, a subject S acquires a new feature (accident). The subject S persists throughout

242 this change. In contrast, in a substantial change, the original subject S ceases to exist and gives way to a new subject, S*. Now, to claim that a self-change occurs is to claim that S actualizes one of its passive potencies; S thereby acquires a new feature. This is an instance of accidental change. If S itself failed to acquire a feature, this would not be an instance of accidental change or of self-change.

S would fail to acquire a feature, however, if the putative self-change were to bring into being S*; for

S* replaces S, and S thus does not persist so as to acquire a new feature. In other words, a substantial change and an accidental change cannot occur in the same subject. Therefore, a self- change, which is a type of accidental change, is incompatible with substantial change.

A potential counterexample to the argument above arises in the case of autothysis, a form of insect suicide. In this process, some ants and termites contract the muscles surrounding an internal organ, which consequently ruptures and releases a toxin that harms predators. The rupture quickly leads to the insect’s death, though some species can survive for a few minutes after the initial trauma. This is clearly a case in which a self-change (a self-caused rupture) leads to a substantial change (death).

Autothysis would thus seem to be an instance of an accidental change that results in a substantial change. One might further imagine a scenario in which a self-change triggers a series of events that yield not only a pile of insect parts but a single, new living substance. Why is this type of substantial self-change not possible?

Autothysis and similar processes (if there are any) do not amount to substantial self-change because they are not sufficient causes of substantial change. Consider a scenario in which a self-change C in a subject S does not cause a substantial change but sets in motion a hypothetical series of events leading to a substantial change. In this situation C is not individually sufficient to effect a substantial

243 change; otherwise S would give way to a new substance immediately. Therefore, another change C* must be necessary to effect this substantial change. The question then arises about C*: Is it a self- change or not? If so, then by the argument given above, C* cannot be a substantial change. If C* is instead an externally effected change, then S is not the cause of the substantial change; some other agent is. It is ultimately an external agent E, then, that by its causality determines what substantial form the erstwhile constituents of S will assume. Although S supplies the material that E forms into a new substance, S itself is not responsible for the formation of that matter; the destruction of S is not by itself the formation of the new substance S*. S is therefore not the agent of substantial self- change even when it initiates a process that culminates in a self-change.

To sum up, self-change cannot lead to essential change. Therefore, because organismic development is self-change, it cannot be essential change.45 Thomas’s view of development, and all kindred views that understand development as essential change, are mistaken. Most importantly for the present purposes, these views erroneously posit a rupture in numerical identity during development when there is none.

At this point it is clear that development is self-change and that it preserves numerical identity. The opposing views that reject these characterizations ignore either biological evidence or the metaphysics of self-change. With these conclusions established, however, one may still want a fuller explanation of the self-change involved in development. There is still the appearance of essential

45 To his credit, Thomas never suggests that essential self-change is a possibility. He always maintains that some extrinsic agent is responsible for the alleged essential changes that occur in embryonic development.

244 change occurring when an immature organism acquires the characteristics that define the adult organism. How should we understand the relation of the immature organism to these characteristics? This is a difficult question for the Thomist since Thomas’s own answer has been rejected. Whether his philosophy contains resources for the modern hylomorphic endurantist is our final inquiry.

Developing a Hylomorphic Alternative: A Deeper Understanding of Potentiality The puzzle that developmental self-change presents can be stated simply. Thomas and his contemporary followers, as well as some other philosophers, agree that organisms of kind F must be in potency to φ-ing as a condition of kind membership. However, the function and structure of embryonic Fs are such that they have no ability to φ. Accordingly, it appears that these embryonic organisms cannot be said to possess the requisite potency for their kind. This leads to the conclusion that embryonic Fs are not Fs after all. The intrinsically driven nature of developmental self-change makes this conclusion unacceptable, so an alternative account of embryonic potentiality is necessary.

As noted earlier, Thomas’s exact views on the relationship between an embryonic organism and its later stages are unclear. More importantly for the present inquiry, three reconstructions of Thomas’s views fail to solve the puzzle at hand. Recall Pasnau’s reconstruction (FAC), which says that belonging to kind F is equivalent to possessing the structures necessary to perform the proper operation of kind F. Early embryos clearly do not have the structures needed to engage in the proper operation immediately, so this criterion counts embryos as non-Fs. Thus, this criterion is

245 inadequate, and so is its weaker counterpart, WFAC. That reconstruction is the same as Pasnau’s except that it also grants kind membership to individuals who could perform the proper operation of kind F if some physical impediment were removed. The primary reason that an embryo cannot engage in a proper operation is not any impediment but a lack of physical development, so this criterion also excludes them from kind membership. Finally, CFAC extends kind membership to all individuals included in WFAC and individuals who would be capable of engaging in a given proper operation if their development had not gone awry. This reconstruction, too, excludes embryos from kind membership, for it is not physical malformation that prevents embryos from performing the proper operations of their kinds. Regardless of whether they are good interpretations of Thomas,

CFAC, WFAC, and FAC cannot be components of hylomorphic endurantism, for they fail to characterize embryonic potentiality correctly.

The fourth alternative, EPFAC, looks more promising philosophically but more dubious exegetically. As Haldane and Lee characterize EPFAC, kind membership requires that individuals possess the epigenetic primordia of the organs necessary for the proper operations of their species.

In other words, to be members of kind F, individuals must have some components that initiate internal processes culminating in the development of the organs that support the kind’s proper operation. This view plainly classes embryos as members of the same kinds as mature organisms once the findings of modern developmental biology are admitted. Philosophically, then, this is an encouraging start for a hylomorphic endurantist.

Turning to the evidence for such a view in Thomas’s writings, the picture is at first bleaker. Haldane

246 and Lee claim that Thomas’s philosophical principles, when united with the findings of modern embryology, imply EPFAC.46 Although their article leaves it unclear exactly what these principles are, they do mention a single “metaphysical point” that undergirds his view.47 On this point, they quote the Summa theologiae as follows:

Now it belongs to the natural order that a thing is gradually brought from potency to act. And therefore in those things which are generated we find that at first each is imperfect and afterwards is perfected.48

This is to say that natural things are all such that they move from a state of potency to a state of act.

Obviously Thomas endorses this principle, but, when applied to embryological development, it states merely that there is a relationship of potency and act between immature natural things and mature ones. That there should be numerical identity between the embryo and adult organism does not follow. Even if we grant this identity, it is unclear how we should characterize the embryo’s state of potentiality. It is clearly not a state of first act, a disposition to engage in an activity, but Thomas does not seem to name another sort of potentiality that would preserve numerical identity.49 Where

Haldane and Lee find EPFAC in Thomas’s writings is a mystery.

Nonetheless, it is possible to find a basis for elements of Haldane and Lee’s reconstruction in

46 Haldane and Lee, p. 268. 47 Haldane and Lee, p. 272. 48 ST I, q. 119, a. 2, co. I have presented the quote as cited by Haldane and Lee verbatim. 49 Thomas treats first act and second act as analogous concepts. In many circumstances, he describes first act as the act by which a substantial form informs matter and second act as the operation of a form; see, for instance, Quaestiones de Veritate q. 27, a. 3, ad 25. However, Thomas also calls habits or dispositions “first acts” and the exercise of these habits “second acts”; see the Summa theologiae references in the following notes. When he needs to distinguish the state of being informed by a substantial form from the possession of a habit, he refers to the former state as “primary potency” (to possessing a habit) and to the possession of the habit as “first act” or “second potency”; see Sentencia libri De anima II, l. 11, n. 5.

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Thomas’s writings on moral dispositions or habits. In these writings, Thomas confronts a philosophical puzzle: can an agent be the cause of its own perfection, its own movement from potentially having a disposition to act well to actually having such a disposition? Construing human action as a form of self-change, Thomas says yes. A contemporary Thomist examining today’s embryology might see in this material a model for discussing potentiality in development. In this remainder of this chapter, I will explore how far one can take this model.

Note that the following view is not necessarily the one that Thomas would endorse were he alive today. Trying to divine the response of a bygone great philosopher to evidence he never saw is a fool’s errand. When confronted with a novel philosophical challenge, great minds make new distinctions, foresee new objections, and arrive at conclusions that ordinary thinkers do not. We have little basis for predicting Thomas’s considered responses to contemporary scientific findings.

Nonetheless, when called upon to understand these findings for ourselves, his philosophy offers some useful tools for the task.

To see how Thomas’s writing on habits sheds light on development, it is first necessary to understand what he means by “habit.” He characterizes a habit as a quality that disposes its subject well or poorly toward some object.50 Thomas elaborates that this object may be the subject’s nature itself, an operation of the subject, or a product of that operation. In every case, the habit is ordered toward an act, either because the object itself is an act (as with an operation), or because the object

50 ST I.II, q. 49, a. 1, co.

248 itself is ordered toward an act (as with a nature).51

In the absence of the habit, the subject stands in some relation of potentiality to these three types of objects and might be further actualized (e.g., actually perform an operation) in any of several incompatible manners. The habit determines the manner in which this actualization occurs; more specifically, it determines whether this actualization is done well or poorly. The possessor of a habit, then, is still in a state of potentiality vis-à-vis some act, but this potentiality is not open-ended; it is a potentiality for acting in a certain way.52 Habit is therefore a kind of first act, and it disposes the subject to second act, or operation, in a specific manner.

The formation of habits is a type of self-change. Thomas, unlike Aristotle, reserves habits solely for human acts (i.e., willed acts): only acts chosen by an agent are facilitated by habits.53 In the Thomistic picture, habits are the result of human acts that shape the appetitive and apprehensive powers of the agent. These powers, after the repetition of similar acts, grow more or less influenced by correct reason. In this instance of self-change, reasons for acting or propositions serve as extrinsic causes that act upon the practical or speculative intellect. The intellect then acts upon the various passive appetitive or apprehensive powers to suppress or intensify natural inclinations and intellectual operations.54 The agent thus plays a central role in the formation of his or her own habits by

51 ST I.II, q. 49, a. 3, co. 52 ST I.II, q. 49, a. 4, co. 53 On this difference see Bonnie Kent, “Dispositions and Moral Fallibility: The Unaristotelian Aquinas,” History of Philosophy Quarterly 29.2 (2012), p. 147. 54 ST I-II, q. 51, a. 3, co.

249 engaging in acts that create those habits. In the case of moral habit formation, for instance, the agent moves from simply being able to act to being able to act well or badly, rightly or wrongly.

When describing habit formation, Thomas makes more distinctions about potentiality than he does elsewhere. His discussions of potentiality typically focus on two relationships: prime matter’s potential for substantial form and an individual substance’s potential for acquiring an accident.55

Although habit formation always concerns potentialities of the latter type, the subject stands in various degrees of proximity or remoteness to the accident in question. As noted above, this accident is a particular operation, an action. The agent may be stand in one of several relations to this action. First, she may be capable of performing this action in the absence of the necessary habit, but only inconsistently or with partial success. In the case of playing the guitar, for instance, the untrained player is capable of a performance, but only a rather unmusical one. Nonetheless, she is potentially a guitar player—she is trainable—which cannot be said of unintelligent substances, such as a hermit crab or a water molecule. Second, she may possess the habit needed to perform the action with consistent success. A trained guitarist has actualized her potentiality for playing the guitar so that she can play well when she chooses; she is in a state of first act. Finally, she may actually exercise this habit. This final actualization of her potentiality in a performance is second act. These three instances represent increasing degrees of actualization of potentiality for performing the same type of action.

55 See, for instance, De principiis naturae c. 1.

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Given that habit formation occurs through a series of actions, at what point can an agent be said to possess a habit? Strictly speaking, an agent has a habit only when a particular judgment of reason can incline the relevant appetitive power toward the action designated by reason. Thomas characterizes the action of reason as a “conquest” of the appetites: “[Prior to the acquisition of a habit] the appetitive power is not completely overcome so that it is directed to the same thing in most cases, as happens with nature, which distinguishes the habit of virtue.”56 Despite setting consistency in choice as a hallmark of habit possession, Thomas acknowledges that one can possess habits in a weaker sense. Addressing whether virtues (a type of habit) are possessed naturally, Thomas responds that they are not in the strict sense. However, he adds that agents do have virtues incipiently (in inchoationem) as a result of basic principles of knowledge and action that are natural to rational beings:

[V]irtue in an incipient form is natural to man. This follows from the nature of the species insofar as in human nature there reside certain naturally known principles of knowledge and action, which are the seedbeds of the intellectual and moral virtues. It is also true insofar as there exists in the will a natural appetite for the good that accords with reason.57

Accordingly, although humans are not naturally wise, or just, or otherwise virtuous, they start with an aptitude for those virtues. This is not a powerful aptitude, one that is realized in all but the most unfavorable circumstances, but it is more than mere compatibility, such as being indifferently disposed to wearing clothes of different colors. For an immature agent, then, one cannot truly say,

“He is virtuous,” but one can say, “He is precisely the sort of being that is virtuous.”

56 ST I-II, q. 51, a. 3, co., Leon. 6.328. “Unde ex hoc non totaliter vincitur appetitiva potentia, ut feratur in idem ut in pluribus, per modum naturae, quod pertinet ad habitum virtutis.” 57 ST I-II, q. 63, a. 1, co., Leon. 6.406. “Utroque autem modo virtus est homini naturalis secundum quandam inchoationem. Secundum quidem naturam speciei, inquantum in ratione homini insunt naturaliter quaedam principia naturaliter cognita tam scibilium quam agendorum, quae sunt quaedam seminalia intellectualium virtutum et moralium; et inquantum in voluntate inest quidam naturalis appetitus boni quod est secundum rationem.”

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The potentiality of agents for habits offers further ways to think about the potentiality of embryonic substances for the proper operations of their kinds. Embryos, like agents devoid of habits, have not yet reached a state of first act with respect to these operations. Both groups stand in another relation of potentiality to the operations in question. They are disposed to engage in these operations following upon the proper sort of self-change: development in the case of embryos and deliberate action in the case of agents. Should this self-change proceed properly, both groups will attain a state of first act. In this way, they are distinguished on the one hand from beings for which there is no possibility of being able to engage in a certain operation, and on the other hand from members of their own kinds who have attained such abilities.

Thomas’s claim that agents naturally possess “seedbeds” of the virtues is suggestive of a model for

EPFAC. The inchoate virtues play much the same role in habit formation that Haldane and Lee assign to the epigenetic primordia in development. In light of having the beginnings of the virtues, agents can be said to be naturally virtuous, if only in an attenuated fashion. Similarly, by having the primordia of the organs that support intellectual activity, embryos could be considered fully members of their kinds, despite attaining to the necessary sorts of first act only in a very limited manner, which is the germ of the complete state of first act.

The sort of potentiality at play in development also becomes clearer through the contrast between development and habit formation. The latter process transpires through human acts that aim at a

252 variety of goods. The formation of habits is not necessarily the end of these acts, and the nature of the habits that emerge is contingent upon the choices of the agent. Embryonic development, in contrast, is a natural process that tends toward a single end, the maturity of the individual. The potentiality of the embryo, then, is determinate in the way that the potentiality of an agent is not. It is possible to specify in advance the structures and activities of an embryo when it becomes a mature individual. This is not possible with an agent. Therefore, the embryo possesses a potentiality for first act with respect to its proper operation to a greater extent than an agent that has some such potentiality with respect to any particular habit. If it is possible to characterize an immature agent as the sort of being that is virtuous, it is far more appropriate to characterize an embryo as the sort of being that engages in the proper operation of its kind. The former characterization abstracts from the contingencies of deliberate action, while the latter rests on the predictable course of natural development.

These considerations make EPFAC a plausible addendum to hylomorphic endurantism, even though Thomas never endorses this claim. By making this addition, HE refines Thomas’s understanding of the matter required for kind membership and by extension the sort of changes that an individual may endure while remaining numerically the same. For matter to be adequate for a given animate substantial form, it need only possess the precursors of the structures required for the proper operation of that form. These structures in their current state may not be consistent with the ability to perform the proper operation; they simply need to be developing toward that state.

From this relaxed criterion of kind membership follows greater toleration for changes within

253 numerically the same organism. The development of the primordia of mature biological structures does not constitute a progression from one kind of organism to the next; rather, the very same organism gradually comes to exhibit the full actuality of its substantial form. Numerically the same creature persists throughout embryonic development as the distinctive features and activities of its kind become more manifest.

Grounding this numerical identity are, of course, the identity of the individual’s substantial form and the continuity of its matter. The substantial form is responsible for both for the individual’s being a member of a certain kind and for the trajectory of its development, which leads the individual to acquire the capacity to engage in the distinctive activities of that kind. The continuity of matter ensures that there is a persisting subject for this form. Therefore, although the claims of hylomorphic endurantism extend beyond anything defended by Thomas and occasionally conflict with his thought in important ways, the underpinnings of this theory of diachronic identity are robustly Thomistic.

Final Remarks Hylomorphic endurantism can plausibly draw on Thomas’s thought to articulate why organisms are numerically identical through development and how earlier phases of development relate to later ones. Specifically, Thomas’s discussion of potentiality in the context of habit formation shows how we can characterize the potentiality of a juvenile organism for the features of a more mature organism. To be sure, there is much more to say about these relationships; for instance, it is clear that the Thomistic characterization of “vegetative” or “nutritive” activities needs to include a power

254 of differentiation to better explain intrinsically guided development. How this power relates to the organism’s essence and to its “mature” powers also requires more attention.

Development, though an important subject in a study of diachronic identity, is not the final source of puzzles. There are numerous kindred problems that remain untouched in this work: twinning and other forms of fission, brain transplantation, and problems of psychological discontinuity, among others. These all deserve further attention. They are not foundational problems, however, and I am confident that HE as it is outlined here furnishes the metaphysical apparatus for addressing these and similar puzzles. It remains, then, for a future work to explore these further challenges and to build upon the foundation of hylomorphic endurantism.

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CONCLUSION

With the argument of this work completed, it is possible to see how hylomorphic endurantism fares vis-à-vis the demands for a theory of diachronic identity sketched at the outset of this dissertation.

These criteria have emerged with more clarity and color in the course of the investigations of the various chapters, so it is worthwhile to restate them here in more finished form:

1. Elucidating and, if possible, defending a notion of identity that respects and explains the

prevalence of common intuitions and everyday puzzles about identity.

2. Addressing (and possibly explaining away) the principal puzzles about diachronic identity in

philosophical literature.

3. Providing a theory with explanatory power, that is, a theory whose claims rest on a well-

defined conceptual framework.

4. Developing the conceptual apparatus to make sense of identity through self-change.

The first of these demands received the most attention in discussions of Leibniz’s Law, more precisely the Indiscernibility of Identicals. The Law holds that numerical identity requires sameness with respect to every feature; everyday speech and thought suggest that this rule of identity applies only to synchronic identity; and philosophers disagree over whether the Law governs synchronic and diachronic cases alike. The chief argument against applying the Law to one “type” of identity but not the other is that identity is one phenomenon, not two, so requirements should be the same in synchronic and diachronic cases. Hylomorphic endurantism deflects this criticism by explaining how being numerically the same substance is compatible with a change in features over time. Because

256 substantial identity depends only on the identity of substantial form and the continuity of matter, the alteration of features does not by itself equate to a change in identity. This position makes room for pre-philosophical belief that individuals can remain the same despite changing with respect to some features. Our everyday speech and thought are not wrong, imprecise, or even underdetermined because they characterize identity in this way. Rather, our behavior is explicable and justifiable in light of truths about identity that HE brings to light. HE makes our thoughts and sayings intelligible

—when other theories do not—and this is a great strength of the theory.

Faced with the demands of the second criterion, HE shows that it is not simply a theory of everyday thought and behavior (what P.F. Strawson would term “descriptive metaphysics”). Rather, the theory takes seriously and solves the puzzles about diachronic identity that dominate the philosophical literature. I just recapitulated HE’s approach to the Indiscernibility of Identicals, so I will focus on the other two major puzzles. The problem of temporary intrinsics, on closer analysis, turns out to be no problem at all. This vacuity is intrinsic to the problem; it is not a flaw that follows only from accepting certain tenets of HE. However, HE offers a unique response to the question that seems to underlie the problem of temporary intrinsics, namely, “How can an object be wholly present throughout time if it loses and gains contingent features?” HE replies by pointing to its ontological foundations: being this whole amounts to being this individual substance, and only changes that preclude the identity of substantial form or the continuity of matter interfere with substantial identity. Because most changes in contingent features do not have these effects on substantial form and matter, these changes generally do not create barriers to substantial identity.

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The last puzzle considered was the Problem of Material Constitution (PMC). Solving this collection of puzzle cases turns on HE’s distinction between substances and aggregates. Here again the resources of Thomistic metaphysics hold the key to the problem. HE offers principled solutions because it draws on previously tested principles.

HE is more successful than other endurantist theories in its approaches to puzzle cases, but it is not unique in attempting to provide solutions. The theory differs most markedly from rival versions of endurantism in satisfying the last two criteria listed above. With regard to explanatory power, the distinguishing aspect of HE is abundantly clear already: ontology, ontology, ontology. Because the theory builds on Thomas’s metaphysics, it has at its disposal an independently substantiated framework of concepts and principles to deploy in elucidating the notion of substantial identity. For instance, whereas Merricks holds that there can be no meaningful criterion of identity, HE readily can show how there are in fact meaningful criteria: the identity of some entities (e.g., substances) depends on the identity of other entities (e.g., substantial form and matter). Similarly, HE not only can refute perdurantist views about Leibniz’s Law, but the theory also can put a sensible, independently motivated view in their place because it has a rigorous notion of substantial identity on hand.

The ontological foundation of HE also enables us to venture beyond the bounds of standard puzzles to make sense of problems that have received little attention. Few authors address self- change as such, though many consider specific instances in the context of bioethics. Nonetheless, phenomena such as embryonic development and self-destruction pose new questions for theories of

258 identity and therefore deserve scrutiny. The HE approach to these questions highlights the attitude I have tried to maintain toward Thomas’s writings throughout this work, which is a combination of deep appreciation and critical reflection. Thus, while proposing an understanding of development very different from his, I address not only his outmoded biology, but interpretations of his views on kind membership, which remain relevant today.

HE’s success in satisfying these criteria manifests its robustness. As a theory planted in the rich soil of Thomistic ontology, HE has deep metaphysical roots. It also has many offshoots, implications for other areas of identity not explored in this work. The most obvious is a more complete view of identity, one that considers not only material substances but also other types of entities. How should one understand the identities of properties, relations, and events? Are there non-substantial entities that perdure, even if substances endure? Along related lines, there are secondary puzzles in the literature that I have not discussed, such as twinning (and fission more generally), fusion, and brain transplants. Interesting as these are, they deserve attention only after the groundwork for a theory of diachronic identity is in place. Investigating them can wait for another occasion.

Hopefully chapter 5 left no doubt that there is a great need for further study of a topic closely related to identity, development. The philosophy of biology of course concerns itself with this subject, but investigations should not be confined to that field. Nor would it be enough to further scrutinize the topic of generation and the associated loci classici. This is quite clear one we briefly reflect on the scope of the concept of development; it is vast. The notion of development encompasses virtually all becoming: most (certainly not all) constructions involving forms of

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‘become’ can be restructured as constructions with ‘develop’ (e.g. ‘develop into’).58 There are thus impersonal and non-biological instances of development, such as a tropical storm developing into a hurricane or a slogan developing into a creed, that mark out development as a phenomenon of general metaphysical interest. Moreover, development often is an internal process of realizing an internal potentiality, such as a boy becoming a man, rather than a generation of something altogether new. Literature in the Aristotelian tradition, which tends to view change as either generation, alteration, or quantitative growth, suffers from a blind spot with regard to development.

This work also suggests further directions for Thomistic scholarship. There is more to say about

Thomas’s views on identity, and comparatively little written on the subject. His contrast between permanent and successive entities, for instance, appears to have received no extended treatment. His thoughts on the identity of matter are reviewed in a dissertation,59 but seemingly nowhere else. To mention just one more topic, a Thomistic view of development. As chapter 5 showed, this cannot be a straightforward exposition or interpretation of Thomas’s thought, for he lacks an understanding of the phenomena of development as we know them today. I have offered a preliminary sketch of how one could employ Thomistic concepts to fashion a theory of development, but a comprehensive effort would entail further elucidation of the basic concept of development, as noted above.

58 Setting aside instances in which ‘to become’ means ‘to be fitting for,’ there are some constructions with ‘become’ that have no equivalent using ‘develop.’ For instance, ‘it became dark’ cannot be restated as ‘darkness developed’ or ‘it developed into dark.’ 59 Silas Langley, “Aquinas on Human Life After Death” (PhD diss., Fordham University, 2002).

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There is, then, a great deal about identity that is not well-studied. Hylomorphic endurantism represents the first step in a serious investigation of identity; it is not remotely close to being the final word. Some of the misconceptions that were barriers to understanding are now gone, and there are guidelines to direct further inquiry. Much more, however, remains to come.

BIBLIOGRAPHY

Primary Texts

Thomas Aquinas. In Aristotelis libros Metaphysicorum. Edited by M.R. Cathala and R.M. Spiazzi. Turin: Marietti, 1950.

———. Opera omnia. Vol. 11, Commentum in quartum librum Sententiarum magistri Petri Lombardi (continuatio). Paris: Louis Vivès, 1873.

———. Quaestiones disputatae. Vol. 2, Quaestiones disputatae de potentia. Edited by P.M. Pession. Turin- Rome: Marietti, 1953.

———. Sancti Thomae de Aquino Opera omnia, Leonine edition. Rome, 1882—. Vols. 4-12, Summa Theologiae. Vols. 13-15, Summa contra Gentiles. Vols. 22.1, 22.2, 22.3, Quaestiones disputatae de veritate. Vol. 40, Quaestiones disputatae De anima. Vols. 25.1, 25.2, Quaestiones de quolibet. Vol. 42, Compendium theologiae. Vol. 43, De principiis naturae, De mixtione elementorum, De ente et essential, etc. Vol. 50, Super Boetium De Trinitate, Expositio libri Boetii De ebdomadibus.

———. Scriptum super libros Sententiarum. Vols. 1 and 2. Edited by R.P. Mandonnet. Paris: Lethielleux, 1929.

———. Scriptum super libros Sententiarum. Vols. 3 and 4. Edited by M.F. Moos. Paris: Lethielleux, 1933 and 1947.

John Duns Scotus. B. Ioannis Duns Scoti Opera philosophica. Vols. 3-4, Quaestiones Super Libros Metaphysicorum Aristotelis. St. Bonaventure, NY: Franciscan Institute, 1997.

Secondary Texts

Amerini, Fabrizio. Aquinas on the Beginning and End of Human Life. Translated by Mark Henninger. Boston: Harvard University Press, 2013.

Baker, Lynne Rudder. Persons and Bodies. Cambridge: Cambridge University Press, 2000.

Balashov, Yuri. “Enduring and Perduring Objects in Minkowski Space-Time.” Philosophical Studies 99, no. 2 (2000): 129-66.

Bobik, Joseph. Aquinas on Matter and Form and the Elements. Notre Dame, Indiana: Notre Dame University Press, 1998.

261

Brower, Jeffrey. Aquinas’s Ontology of the Material World. Oxford: Oxford University Press, 2014.

———. “Aristotelian Endurantism: A New Solution to the Problem of Temporary Intrinsics,” Mind 119 (2010): 883-905.

———. “Matter, Form, and Individuation.” In The Oxford Handbook of Aquinas, edited by Brian Davis and Eleonore Stump, (New York: Oxford University Press, 2012), p. 88.

———. “Medieval Theories of Relations.” In The Stanford Encyclopedia of Philosophy. 2013. http://plato.stanford.edu/entries/relations-medieval/#3.

Brown, Christopher. Aquinas and the Ship of Theseus: Solving Puzzles about Material Objects. London and New York: Continuum, 2005.

Brown, Mark T. “The Potential of the Human Embryo.” Journal of Medicine and Philosophy 32, no. 6 (2007): 585 – 618.

Crisp, Thomas, and Donald Smith. “‘Wholly Present’ Defined.” Philosophy and Phenomenological Research 71, no. 2 (September 2005): 318-344.

Dewan, Lawrence. “St. Thomas, Joseph Owens, and Existence.” The New Scholasticism 56 (1982): 399-431.

Ford, Norman. When Did I Begin? New York: Cambridge University Press, 1988.

Geach, Peter. Logic Matters. Oxford: Basil Blackwell, 1972.

———. Reference and Generality. Ithaca, NY: Cornell University Press, 1980.

Gilbert, S.F. Developmental Biology, 6th ed. Sunderland, MA: Sinauer Associates, 2000.

Gracia, Jorge. “Numerical Continuity in Material Substances: The Principle of Identity in Scholastic Metaphysics.” Southwest Journal of Philosophy 10 (1979): 73-92.

Haldane, John, and Patrick Lee. “Aquinas on Human Ensoulment, Abortion and the Value of Life.” Philosophy 78 (April 2003): 255-78.

Haslanger, Sally. “Endurance and Temporary Intrinsics.” Analysis 49 (1989): 119-125.

Heller, Mark. “Things Change.” Philosophy and Phenomenological Research 52 (1992): 695-704.

———. “Varieties of Four Dimensionalism.” Australasian Journal of Philosophy 71, no. 1 (March 1993): 47-59.

Hinchliff, Mark. “The Puzzle of Change.” Philosophical Perspectives 10 (1996): 119-36.

262

Howsepian, A.A. “Four Queries Concerning the Metaphysics of Early Human Embryogenesis.” Journal of Medicine and Philosophy 33, no. 2 (2008): 140-157.

Hume, David. A Treatise of Human Nature. Edited by David Fate Norton and Mary J. Norton. New York: Oxford University Press, 2005.

Johnston, Mark. “Is There a Problem About Persistence?” Proceedings of the Aristotelian Society, Supp. vol. 61 (1987): 107-135.

Kent, Bonnie. “Dispositions and Moral Fallibility: The Unaristotelian Aquinas.” History of Philosophy Quarterly 29, no. 2 (2012): 141-57.

King, Peter. “Duns Scotus on the Reality of Self-Change.” In Self-Motion from Aristotle to Newton, edited by Mary Louise Gill and James G. Lennox, 227-290. Princeton, NJ: Princeton University Press, 1994.

Langley, Silas. “Aquinas on Human Life After Death.” PhD diss., Fordham University, 2002.

Lewis, David. On the Plurality of Worlds. Oxford: Blackwell, 1986.

Lombard, Lawrence. “The Doctrine of Temporal Parts and the No-Change Objection,” Philosophy and Phenomenological Research 54 (1994): 365-73.

Markosian, Ned. “The 3D/4D Controversy and Non-Present Objects.” Philosophical Papers 23 (1994): 243-49.

Maunu, Ari. “Indiscernibility of Identicals and Substitutivity in Leibniz.” History of Philosophy Quarterly, 19, no. 4 (2002): 367-80.

McKinnon, Neil. “The Endurance/Perdurance Distinction.” Australasian Journal of Philosophy 80, no. 3 (September 2002): 288-306.

McMahan, Jeff. “Killing Embryos for Stem Cell Research.” Metaphilosophy 38 (2007): 170–189.

Merricks, Trenton. “Endurance and Indiscernibility.” The Journal of Philosophy 91 (1994): 165-84.

———. “On the Incompatibility of Enduring and Perduring Entities.” Mind 104 (1995): 523-31.

———. Objects and Persons. Oxford: Clarendon Press, 2001.

———. “Persistence, Parts, and Presentism.” Noûs 33 (1999): 421-38.

———. “There Are No Criteria of Identity over Time.” Noûs 32, no. 1 (1998): 106-124.

Montague, Phillip. “Stem Cell Research and the Problem of Embryonic Identity.” Journal of Ethics 15, no. 4 (2011): 307-319. 263

Oderberg, David. “Hylemporphic Dualism.” In Personal Identity, edited by Ellen Frankel Paul, Fred Miller, and Jeffrey Paul, 70-99. Cambridge: Cambridge University Press, 2005.

———. Real Essentialism. London: Routledge, 2008.

———. “Temporal Parts and the Possibility of Change.” Philosophy and Phenomenological Research 69, no. 3 (November 2004): 686-708.

Olson, Eric. The Human Animal. New York: Oxford University Press, 1997.

———. “Was I Ever a Fetus?” Philosophy and Phenomenological Research 57, no. 1 (1997): 95-110.

———. “Why I Have No Hands.” Theoria 61 (1995): 182-97.

Owens, Joseph. “Material Substance—Temporal or Eviternal?” The New Scholasticism 56 (1982): 442- 61. ———. “Thomas Aquinas (b. ca. 1225; d. 1274).” In Individuation in Scholasticism: The Later Middle Ages and the Counter Reformation, edited by J.J.E. Gracia, 173-94. Albany, NY: SUNY Press, 1994. Pasnau, Robert. Thomas Aquinas on Human Nature: A Philosophical Study of Summa Theologiae, 1a 75-89. Port Chester, United Kingdom: Cambridge University Press, 2001.

Rea, Michael. “Constitution and Kind Membership.” Philosophical Studies 97, no. 22 (January 2000): 169-93.

———. “The Problem of Material Constitution.” The Philosophical Review 104, no. 4 (October 1995): 525-52.

———. “Temporal Parts Unmotivated.” The Philosophical Review 107, no. 2 (1998): 225-60.

Rota, Michael. “Substance and Artifact in Thomas Aquinas.” History of Philosophy Quarterly 21, no. 3 (July 2004): pp. 241-259.

Sider, Theodore. Four Dimensionalism. Oxford: Oxford University Press, 2001.

Simons, Peter. Parts: A Study in Ontology. Oxford: Oxford University Press, 1987.

Stump, Eleonore. Aquinas. New York: Routledge, 2003.

———. “Emergence, Causal Power, and Aristotelianism in Metaphysics.” In Power and Capacities in Philosophy: The New Aristotelianism, edited by John Greco and Ruth Groff, 48-68. New York: Routledge, 2013.

264

———. “Non-Cartesian Substance Dualism and Materialism without Reduction.” Faith and Philosophy 12 (October 1995): 505-531.

———. “Resurrection, Reassembly, and Reconstitution: Aquinas on the Soul.” In Die menschliche Seele: Brauchen wir den Dualismus? Edited by B. Niederbacher and E. Runggaldier, 151-72. London: Ontos Verlag, 2006.

Takho, Tuomas. “Ontological Dependence.” In The Stanford Encyclopedia of Philosophy. 2015. http://plato.stanford.edu/entries/dependence-ontological/#VarOntDep.

Toner, Patrick. “Emergent Substance.” Philosophical Studies 141, no. 3 (December 2008): 281-97.

———. “On Aristotelianism and Structures as Parts.” Ratio 26, no. 2 (June 2013): 148-61.

Torrell, JeanPierre. Saint Thomas Aquinas. Vol. 1, The Person and His Work. Translated by Robert Royal. Washington, D.C.: The Catholic University of America Press, 1996.

Van Inwagen, Peter. “Four Dimensional Objects.” Noûs 24 (1990): 244-55.

———. Material Beings. Ithaca, NY: Cornell University Press, 1990.

Wasserman, Ryan. “Framing the Debate over Persistence.” Metaphysica 5 (2004): 69-73.

Whelton, Beverly. “Human Nature, Substantial Change, and Modern Science: Rethinking When a New Human Life Begins.” Proceedings of the American Catholic Philosophical Association 72 (1999): 305-313. Wiggins, David. “On Being in the Same Place at the Same Time.” The Philosophical Review 77 (1968): 90-95.

Wippel, John. The Metaphysical Thought of Thomas Aquinas. Washington, D.C.: The Catholic University of America Press, 2000.

———. “Thomas Aquinas’s Derivation of the Aristotelian Categories (Predicaments).” Journal of the History of Philosophy 25, no. 1 (1987): 13-34.

Zimmerman, Dean. “Persistence and Presentism.” Philosophical Papers 25 (1996): 115-26.

265