Chapter 1.

The Problem of Life's Definition

The 'mystery' of consciousness today is in roughly the same shape that the mystery of life was before the development of molecular biology or the mystery of electromagnetism was before Clerk-Maxwell's equations. It seems mysterious because we do not know how the system of neuro-physiology/ consciousness works, and an adequate knowledge of how it works would remove the mystery. (Searle 1992, 101-2)

The philosophical literature is positively rife1 with claims similar to those made in the epigraph, claims to the effect that the nature of life no longer presents interesting philosophical questions. The field of Artificial Life — a field which bears essentially the relationship to biology that Artificial Intelligence research bears to psychology2 — is currently bringing the nature of life and

1 In addition to Searle's comment, see Searle (1997, 201), Cornman (1992, 5), Crane (1995, 4-5), McGinn (1991, 6, 8, & 45), & Chalmers (1996, 25). The view is commonplace in science as well. Boyce Resenberg says, "life is just so much chemistry and physics", and he quotes biologist Harold Erikson as saying, "The secret of life is not a secret anymore. We have known for twenty or thirty years now that life is not more mysterious than the chemical reactions on which it is based." Cell biologist Tom Pollard is quoted as saying (what may be something quite different) that "What molecular biologists have believed for two generations is now generally regarded as proved beyond any doubt. Life is entirely the result of physics and chemistry inside cells and among cells" (Rensberger 1996, 25. Emphasis added.). Against this view, see Kraemer (1984). 2 See Bedau (1992b); also Sober (1992) for necessary qualifications to the claim. It is perhaps best to let some of Artifical Life's (AL) leading practitioners describe the nature of AL research. Bonabeau and Theraulaz define AL thus: "We consider it as a general method consisting in generating at a macroscopic level, from microscopic, generally simple, interacting components, behaviors that are interpretable as lifelike" (1995, 303). Here is T. Ray on AL: "Artificial Life (AL) is the enterprise of understanding biology by constructing biological phenomena out of artificial components, rather than breaking natural life forms down into their component parts. It is the synthetic rather than the reductionist approach.... The umbrella of AL is broad and covers three principle approaches to synthesis: in hardware (e.g., robotics, nanotechnology), in software (e.g., replicating and evolving computer programs), and in wetware (e.g., replicating and evolving organic molecules, nucleic acids, or others).... I would like to suggest that software syntheses in AL could be divided into two kinds: simulations and instantiations of life processes. AL simulations represent an advance in biological modeling, based on a bottom-up approach, which has been made possible by the increase of available computational power.... In simulation, data structures are created that contain variables that represent the states of the entities being modeled. The important point is that in simulation, the data in the computer is treated as a representation of something else, such as a population of mosquitoes or trees. In instantiation, the data in the computer does not represent anything else. The data patterns in an instantiation are considered to be living forms in their own right and are not models of any natural life form. These can form the basis of a comparative biology. The object of an AL instantiation is to introduce the natural form and process of life into an artificial medium. This results in an AL form in some medium other than carbon chemistry and is not a model of organic life forms." (Ray 1995, 179-80)

1 the problematic status of its analysis back into focus, however.3 This chapter's aim is to focus attention on the philosophically rich character of questions concerning what it is to be animate.

The following passage may serve to focus attention on the problematic status of our conception of living:

There is no universally agreed definition of life. The concept covers a cluster of properties, most of which are themselves philosophically problematic.... Theorists differ about the relative importance of these properties, although it is generally agreed that the possession of most (not necessarily all) of them suffices for something to be regarded as alive. It is not even obvious that, as A-Life scientists assume, life is a natural kind. In other words, 'life' may not be a scientifically grounded category (such as water, or tiger), whose real properties unify and underlie the similarities observed in all those things we call 'alive'. (Boden 1996, 1)

The problem of the nature of life is at a troubling crossroad between philosophy and science; scientists tend to find the question 'too philosophical,' whereas philosophers tend to find the question 'too scientific'.4 This conjunction of philosophical and scientific aspects leads into a nest of problems and arguments centering on core questions in the philosophy of biology, the ontology of the physical world, and scientific methodology.

The thesis of this dissertation is that a proper understanding of Aristotle on the nature of life yields an adequate contemporary account of life. Much of the plausibility of this thesis hangs, of course, on the phrase 'proper understanding'. Aristotle is often invoked as an archtypical vitalist; this dissertation attempts to debunk such a view. Aristotle's biology is justly eclipsed; this dissertation argues that this does not undermine the status of his account of life, for our account of living needs to accommodate the possibility of nonbiological life just as Aristotle's does. Aristotle's ontology is often thought to be incompatible with contemporary scientific methodology; I argue that this view is incorrect.

3 As Bonabeau and Theraulaz (1995, 323) remark, "If you are a philosopher, AL will give you the opportunity to think about new issues in ethics, epistemology, and so on and will provide you with years of work to unravel the ontological status of life: you will be able to think over life as no other philosopher before." 4 As noted by Mark Bedau (1996, 496). This conflict is brought into the open by Lange: "Immunologist P.B. Medawar, Nobel laureate in 1960, says that discussions of what it is to be alive 'are felt to mark a low level in biological conversation' (1977, 7), whereas geneticist Joshua Lederberg, Nobel laureate in 1958, writes: An important aim of theoretical biology is an abstract definition of life. Our only consensus so far is that such a

2 The goals of this dissertation are therefore twofold. One goal is to articulate a philosophically sophisticated and textually accurate account of Aristotle on the nature of life. This project involves extended investigation of Aristotle's epistemological and metaphysical grounding of the core notions involved in his account. Second, I seek to defend the view of life that emerges from

Aristotle's work in light of contemporary discussions of the reducibility of teleology to evolutionary adaptation, the ontology of the physical world, and the presuppositions of a successful scientific methodology.

1.1. Dissertation overview.

My strategy is to ease into the deep philosophical issues surrounding Aristotle's account of life through the relatively narrow scholarly elucidation of his views. The goal of this introductory chapter is the modest one of bringing to light a set of issues which mark the status of life as an area ripe for contemporary philosophical investigation. Through critically discussing a number of contemporary accounts of life, I argue that Aristotle holds a surprisingly sophisticated and interesting set of theses in his philosophy of nature; these commitments are currently unrepresented in discussions of the nature of life and amply justify further interest in and investigation of Aristotle's account.

In chapters two through four I begin in earnest the scholarly task of uncovering Aristotle's core theses concerning life and investigating the philosophical presuppositions of the account.

Chapter two critically surveys the contemporary secondary literature on Aristotle's account of life. I endorse the consensus view that Aristotle's conception of life is teleological, but separate this core commitment from the details of the particular accounts. Chapter three defends the provisional teleological account of life by arguing that the scope of Aristotelian teleology is compatible with an account of life in teleological terms. In the course of this defense, I offer a reading of Aristotle's central argument for teleology in Physics ii.8 on which Aristotle's grounds for postulating natural

definition must be arbitrary [since] life has gradually evolved from inanimate matter... (1960, 394)" (quoted in Lange 1996).

3 teleology are moderate, plausible, and widely shared today. Chapter four raises the specter of the deep philosophical and methodological questions to come, however, for I argue in chapter four that

Aristotle's view of the ontic status of final causality is in deep conflict with the presumptive modern realist approach to biological teleology. I argue (against the present trend in the secondary literature on Aristotle) that Aristotle takes the final cause to be a sui generis real causal factor in the structure of the world.

Chapters five and six address the contemporary status of commitment to sui generis teleology.

In these chapters I argue against the consensus theses that (1) the ontology of the physical world has no room for sui generis teleology, (2) the methodology of science cannot survive its postulation, and

(3) an adequate realist yet reductivist account of teleology — or at least the broad outlines of such an account — currently exists. I argue in chapter five that contemporary philosophy of biology provides no adequate reductivist account of teleology, but that the grounds that encourage theorists to be realists rather than eliminitivists concerning teleological commitment survive the failure of these reductive accounts. I argue further that methodological worries about the postulation of sui generis teleology are misguided and may reasonably be allayed — it is no part of this dissertation's thesis that a priorist science should make a comeback.

Chapter six argues that the ontological presuppositions which ground methodological and scientific worries concerning sui generis teleology and the drive for reductivist accounts of teleology

(and mind) are highly suspect; we have good theoretical grounds for supposing that there exists a coherent ontology for the physical world in which sui generis teleology finds a natural home. Further, we have strong evidence from our best science (physics) that this ontology is the ontology of the actual world. Chapter seven pulls together the scientific, philosophical and scholarly threads of the dissertation and presents a formal Aristotelian definition of what it is to be alive. Chapters five and six therefore constitute the contemporary philosophical defense of the core philosophical commitments of Aristotle's account of life. Chapter seven is the culmination of the scholarly task

4 begun in chapters two through four of explicitly formulating and defending Aristotle's account of life.

I turn now to the task of the present chapter: displaying the problematic status of the nature of life in contemporary thought and the promise of an Aristotelian account of life given the contemporary intellectual milieu.

1.2. Life in contemporary biology and philosophy.

This section constitutes an extended introduction to the problem of life's definition. I critically survey a number of modern approaches to the nature of life, raising and defining deep philosophical questions surrounding the issue and the philosophical and scientific presuppositions of such accounts of life as exist. My thesis is the moderate one that the nature of life is a more difficult and a more interesting philosophical problem than most modern treatments suggest.

1.2.1. Biologists on life.

Given the wild success of biology since Darwin, it is attractive to think that we may simply look to the contemporary (flourishing) science of life for a solution to our problem. This subsection's goal is to display the problematic nature of this initially promising idea.

1.2.1.1. Do scientists need a definition of life?

The epigraph that opens this chapter suggests that contemporary biology already reveals the nature of life, but this assumption is highly problematic. Surprisingly, "The problem is that biology seems to have little to tell us about what it is to be alive" (Sober 1992, 375). We expect biologists to answer an intuitively obvious question — what is it that distinguishes the animate from the inanimate? — but we find that working biologists provide no answer.

The explanation of this puzzle appears to be this: biologists have sufficient work investigating the detailed functioning, structures, and evolutionary histories of things that we all intuitively consider to be alive (along with troubling and interesting 'borderline cases'), and they need no explicit account of life to continue this research. Our intuitive grasp of what things are alive is

5 sufficient to ground the science of life without any satisfactory analysis of what it is to be alive.5 The first problem with turning to biology for an account of the nature of life, then, is that in the theoretical areas in which biology has been so wildly successful in the twentieth century scientists operate under the guidance of an intuitive understanding of what things are alive rather than seeking a general definition of life. This constitutes no problem whatsoever for the confirmation of the views about the functioning, structure, and evolutionary histories of organisms that have developed in this thriving field, but it does constitute a problem for the naïve view that the success of the science of life must have included or been based upon an explicit account of life.

1.2.1.2. Must a definition wait on science?

Nevertheless we may have reason to suppose that we must look to empirical research to provide the central theoretical grounds for a proper definition of life. This view is widely held by computer scientists and theoretical biologists working in the field of Artificial Life.6 They motivate the centrality of their work to the definition of life through raising a purported problem for more traditional approaches. The problem is supposed to be that biologists have only one example of life to work with: life as it has evolved here on earth. Christopher Langton has stated the problem vividly: "theoretical biology has long faced the fundamental obstacle that it is impossible to derive general principles from single examples" (1989/ 1992/ 1996, 39).7 8 We may thus formulate a first problem concerning the nature of life, the small sample problem.

5 Mark Bedau and Packard note, "What is life? How can it be recognized? In an everyday context, these questions seem tantalizingly clear—a cat is alive and a rock is not" (1991, 457). John Searle says, "Of course, biologists do not need to be constantly thinking about life, and indeed, most writings on biology need not even make use of the concept of life. However, no one in his right mind denies that the phenomena studied in biology are forms of life" (Searle 1992, 227-8). Kim Sterelny and Paul Griffiths say, "biologists do not need a definition of life to help them recognize what they are talking about" (1999). 6 On Artificial Life, see above, n.2. 7 Eliott Sober says, "The point is that there is little in the way of a principled answer to the question of which features of terrestrial life are required for being alive and which are accidental" (1992, 375). 8 Thomas Ray illustrates the problem by suggesting that our limited grasp of the nature of life prevents us from recognizing the "sentient properties of plants" (1979; cf. 1992b; 1995, 183; Strong and Ray1975).

6 The Small Sample Problem (SS): is the problem of determining from a small sample (in this case a sample of one) which features of some thing (in this case, life) are essential to that thing.

On this view there is a reason that traditional biology has not explicitly answered our question: science is inductive, its method is effective only where we have large numbers of cases to survey. But there is only one kind of life9 — biological life — and so scientific method has up until now been powerless to provide us with a definition.

Artificial Life research is explicitly offered as a solution to this problem by many of its proponents. Thus, Langton says that "our only alternative is to try to synthesize alternative life- forms ourselves" (1989/ 1992/ 1996, 39). The study of AL is, on this construal, partially motivated by the desire to generate a large enough sample of types of life to overcome the (contingent) poverty of examples currently within view and to open the problem of life's definition to proper (i.e., inductive) scientific treatment.10

The small sample problem is a pseudo problem, however, for two reasons. First, the problem appears to presuppose an incorrect view of the scientific method; definitional strategies do not require types of life before they may succeed. On the view which generates the small sample problem the fact that science proceeds inductively entails that we must have types of life to compare before the definition of life can be approached scientifically. But in the sense in which this is true we already possess types of life, for we know of an enormous range of types of living things and we can survey these cases for commonalties and differences. Thus, science is able to discover the chemical essence of water not because we have different types of water to survey but because we have different types of molecules (and atoms). In the only sense in which types of life are required for

9 Note that the problem is not that we lack a sufficient number of living things to study; there are plenty of those. What we lack are types of life itself on Langton's view. 10 Langton explains, "Among all of the things that Artificial Life is or will come to be, however, it is probably safe to say that the field as a whole represents an attempt to increase vastly the role of synthesis in the study of biological phenomena. Synthesis has played a vital role in the grounding of many scientific disciplines, because it extends the empirical database upon which the theory of the discipline is built beyond the often highly accidental set of entities that nature happened to leave around for us to study." (Langton 1995, ix)

7 traditional definitional strategies to succeed we already have numerous types of life and need not wait on the results of AL.

Second, Langton's proposed solution falls prey to a dilemma.11 The dilemma is this: if our grasp of life is sufficient to allow us to distinguish which properties in AL models are relevant to a study of the nature of life, then AL is not the only method available for studying the nature of life for the methods that underpin our selecting between definitional and accidental properties of life in AL models would be sufficient to approach questions of life's account even in the absence of the models.

On the other hand, if our intuitive grasp of life is insufficiently robust to distinguish relevant properties in biological phenomena as they currently exist and as they may begin to make appearances in AL models, then AL cannot overcome SS any more than its more traditional competitors. The upshot is that if the small sample problem is a genuine problem, AL cannot help us solve it, whereas if it is not a problem, then traditional philosophical and scientific methods working on the basis of cases of living things with which we are already familiar can proceed in the absence of AL models.12 Luckily we have reason (given in the preceding paragraph) to suppose that our grasp of life is sufficient for productive work on the nature of life both within and outside of AL research.

The conclusion of this section is a rather moderate one: AL may be a useful tool in our search for a definition of life, but it need not constitute the essential cornerstone of an adequate definition of life.

1.2.1.3. What does biology seem to tell us about life?

Perhaps the core difficulty with turning to biologists for insight into the general nature of life can be illustrated by turning to one biologist's account of the lessons of modern biological inquiry.

11 Arguments of this general type are offered by Bonabeau and Theraulaz (1995), Emmeche (1992, 468), and Nagel (1986, 24). 12 This does not mean that AL models may have no use for theorists concerned to define life; my point in the argument above is not to dismiss the value of the study of AL but to undermine the very strong claim made by some of AL's proponents that only AL can provide the grounds for an adequate definition of life.

8 In The Selfish Gene, Richard Dawkins says of our subject, "Words are only tools for our use, and the mere presence in the dictionary of a word like 'living' does not mean it necessarily has to refer to something definite in the real world" (1989, 18). Dawkins offers an explanation of the origin of life in terms of the tendencies of collections of atoms to settle into relatively stable states. Soap bubbles are spherical because this is a stable configuration for thin films filled with gas; the same shape is stable for water in weightless environments but not on earth. On Dawkins' explanation of life's origin, the tendencies that atoms and molecules have to stabilize in different environments explains the genesis of the first simple replicators as well as the subsequent behavior (including evolutionary change) of those replicators in their environment.13

Dawkins concludes from these reflections concerning life's continuity with nonlife that in some real sense biology has revealed to us that there is no such thing as what it is to be alive, for there are no parts or processes of living things which are distinctive of all and only living things.

Dawkins is happy to employ the term 'life' throughout his book, and to use it to apply to all sorts of things—genes, organisms, populations. Presumably, however, his intent is that a strict reading of any of these uses implies nothing concerning the existence of a property that all and only things classified as 'living' share.

13 The same position is stated with brevity and clarity by Thomas Ray: "Evolution by natural selection.... exploits any inherent self-organizing properties of the medium [into which it enters] and flows into natural attractors realizing and fleshing out their structure.... Evolution is both a defining characteristic and the creative process of life itself. The living condition is a state that complex physical systems naturally flow into under certain conditions. It is a self-organizing, self-perpetuating state of autocatalytically increasing complexity" (Ray 1995, 181). Boyce Rensberger explains, "Crystallization... happens because certain molecules have the innate property of organizing themselves into predictable arrangements entirely without guidance from an outside intelligence.... The key point is that no outside force need guide the events.... This concept of self-assembly is fundamental in today's cell and molecular biology. Under the right conditions, atoms or small molecules automatically link... to form larger structures of absolutely predictable shape. Life's chemistry generally involves very large, highly complex molecules such as the proteins, but these too assemble themselves into still larger, predictable structures" (Rensberger 1996, 22).

9 The general position staked out by Dawkins in this illustration — a position that is widely accepted as correct — contains two14 strands which require separating. The first strand is the empirically supported view that the emergence and nature of life is continuous with and the result of the same processes (iterated many, many, many times) that account for the formation and persistence of soap bubbles.15 The second strand of the position, a strand which is strongly correlated in contemporary work with the first, is the view that because of the continuity we are entitled to conclude that 'life' indicates no natural kind, there is no 'essence' of being alive for science to find, no real (rather than merely conceptual) definition16 to elucidate. Let us formalize these theses:

The continuity thesis (CT): Living things (i) are materially continuous with nonliving things, in the sense that at the borderline of the two classes they fade indistinguishably into one another, and (ii) living things contain no features or properties (except structural properties related to the complexity of their organization) not had by the same material properties and entities outside the context of living things.17

CT entails eliminitivism: There being a real or theoretical definition of life is incompatible with the truth of the continuity thesis.

The most charitable reading of the epigraph that opens this chapter is perhaps that it was this idea, this scientifically grounded scepticism concerning the existence of a unique nonstructural property or activity had only by living things, to which philosophers refer when they express the view that modern of biology has revealed to us the nature of life.18

14 I argue below that there is actually a third distinct strand in the view as expressed by Dawkins and accepted by many contemporaries — a presumption of mechanism. See below pp. 40 ff., for the relevance of this further presupposition of the view. 15 As we will see, Aristotle himself holds this view. 16 For the distinction between real or theoretical definitions and conceptual analyses as it is traditionally employed in this literature, see below, p. 19. 17 cf. Campbell, "The unraveling of the DNA maze has enabled us to discover that even growth, replication, and the transmission of hereditary characteristics are processes of an ordinary chemical kind. The molecules involved are more complex, but the atoms gain no new nature in the living organism." (Campbell 1970, 26) 18 This view is taken by some to have grand consequences for our theories of life and even for philosophy more generally. Dan Dennett claims that Darwin's key insight, the insight that founded modern biology, implied that our intuitions concerning essentialism are fundamentally flawed. Thus, from the Darwinian discovery of the truth of the continuity thesis, we ought to draw morals about the ontology of the world and our epistemic capacities. In a different context Dennett makes this remark, which carries over without distortion to his views on our topic: "The Darwinian perspective lets us see with unmistakable clarity why there is no hope at all of discovering a telltale mark, a saltation in life's processes, that 'counts'.... [T]here is no 'natural'

10 Before criticizing the second thesis, I turn in what follows to address a popular form of

'definition' of life which appears to be motivated by the acceptance of these theses.

1.2.1.4. A weaker notion of definition?

In the face of this eliminitivism about life, many theorists — both philosophers and scientists — have retreated to the position that while science may have shown us that life has no

'strict' definition given in terms of necessary and sufficient conditions, it may nevertheless have a weaker form of 'definition', a cluster definition. The cluster theorist hopes to specify some set of properties that at best 'approximates' necessary and sufficient conditions for life.19 No one theorist takes her cluster to state necessary and sufficient conditions, but cluster theorists fall along a scale from the very anti-essentialist to the 'more' (??) essentialist.

Here is a sampling of the lists of properties that Mark Bedau (1996, pp. 335-6) cites as typical of the offerings of cluster theorists:

Self-reproduction; information storage of self-representation; metabolization; functional interactions with the environment; interdependence of parts; stability under perturbations; the ability to evolve. (Farmer and Belin 1992, 818)

Telenomic or purposeful behavior; autonomous morphogenesis; reproductive invariance. (Monod 1972)

Self-reproduction, genetics and evolution; metabolization. (Crick 1981)

Metabolism, self-reproduction; mutability. (Küppers 1985)

Metabolism; having parts with functions. (Maynard Smith 1986)

Self-reproduction; the capacity for open-ended evolution.20 (Ray 1992a)

way to mark the birth of a human 'soul,' any more than there is a 'natural' way to mark the birth of a species. (1995b, 513) 19 The only sense I can give to the notion of approximating necessary and sufficient conditions is epistemological: the clusters are imperfect epistemic mimics of genuine necessary and sufficient conditions. 20 Ray (1995, 180) comments on the cluster definitions: "Most approaches to defining life involve assembling a short list of properties of life and then testing candidates on the basis of whether or not they exhibit the properties on the list. The main problem with this approach is that there is disagreement as to what should be on the list.... I prefer to avoid the semantic argument and take a different approach to the problem of recognizing life.... Rather than create a short list of minimal requirements and test whether a system exhibits all items on the list, one could create a long list of properties unique to life and test whether a system exhibits any item on the list." Two brief comments on Ray's attitude. First, he takes the issue of life's definition to be

11 1. All levels of living systems have an enormously complex and adaptive organization. 2. Living organisms are composed of a chemically unique set of macro-molecules. 3. The important phenomena in living systems are predominantly qualitative, not quantitative. 4. All levels of living systems consist of highly variable groups of unique individuals. 5. All organisms possess historically evolved genetic programs which enable them to engage in 'teleonomic' processes and activities. 6. Classes of living organisms are defined by historical connections of common descent. 7. Organisms are the product of natural selection. 8. Biological processes are especially unpredictable. (Mayr 1982)

The main appeal of cluster definitions stems from reflections on the continuity thesis and its supposed dire consequences for more robust definitions plus reflections concerning our intuitions about life. The vagueness of the cluster theories allows such accounts to accommodate borderline cases of life — things that we just aren't sure, intuitively, how to categorize as animate or inanimate, e.g. viruses.21 When our intuitions clash with what the cluster theorist's list tells us, our intuitions come out on top.22 The clusters are left vague and imprecise for the purpose of accommodating our unruly intuitions about which things are alive.23

mainly the epistemological issue of getting a scientifically clear criterion up and running for recognizing instances of living things. Indicative of this, Ray considers the main problem with such definitions to be the disagreement people have about what should be on the lists rather than the fact that the lists appear to give neither necessary nor sufficient conditions for being alive. Ray's question should be distinguished from the metaphysical question of the actual analysis of the property of life more clearly than it is. Second, Ray's second "softer, more pluralistic approach" (181) to defining life should remind us of Aristotle's statement that life "has more than one sense, and provided any one alone of these is found in a thing we say that thing is living—viz. thinking or perception or local movement and rest, or movement in the sense of nutrition, decay and growth" (DA 413a23-5). The problems for this sort of 'definition' are treated helpfully by Matthews (1992) and Shields (1999, chapter 7, 'The Meaning of Life'). 21 Spafford (1995, §6 pp. 259-62) applies the list provided by Farmer and Belin (above) point by point to the case of computer viruses. Spafford concludes the computer viruses are not alive (262) after carefully considering how they do on each member of the list along with 'other behavior' (§6.10) but makes no explicit comment on the list provided by Farmer and Belin except that it is a "very reasonable list of properties associated with life" (260). 22 At least in some cases; as with Churchland's handling of counterexamples to his two definitions, there is a bit of the ad hoc in the way that cluster theorists treat the evidence of their preanalytic intuitions about what things are alive. One thing that is clear is that the cluster theories themselves provide no principled way of making decisions in particular hard cases. 23 Mary Anne Warren endorses the cluster 'definitions.' She says, "It should not surprise us that there is no single (or multiple) necessary and sufficient condition for the proper application of the ordinary concept of life.... Basic practical concepts, such as that of life, develop through many generations of experience. Consequently, such concepts often lack the clarity and simplicity that are desirable in, for instance, mathematical or scientific theories.... [T]he complexity and the unclear boundaries of many of our ordinary concepts cannot readily be defined away, except at the cost of substituting a different concept for the original one." (26) After surveying and criticizing Paul Taylor's attempt to do better (in Taylor (1986)), she comments that she thinks "it best to stay with a definition similar to Webster's, i.e. one that lists characteristic features that

12 The vagueness of such 'definitions' contains, however, both their main appeal and the seeds of their ultimate failure. Cluster theorists offer neither necessary nor sufficient conditions for being alive, but offering such conditions constitutes a minimal necessary condition for providing an adequate definition;24 there is a clear sense in which we do not know what something is unless our definition gives us necessary and sufficient conditions. As a further failing, such 'definitions' fail to give any informative explanation for the unity of the cluster of properties cited in the 'definition' — why these properties and no others? Why all of them and not simply some of them or only one?

Gareth Matthews expresses the frustration engendered by so-called 'cluster definitions' in commenting on one such definition offered by The World Book Encyclopedia.25 Matthews comments that,

One doesn't have to be much of a Platonist to become concerned and puzzled about discussions like this. How can it be that only 'nearly all', and not simply 'all', living things have the characteristics that 'outline the basic nature of living things'? And how can a list of characteristics such that only 'nearly all' living things have those characteristics and some non-living things also have them be a list that outlines 'the basic nature of living things'?" (1992, 185)26

Cluster definitions appear not to provide us what we look for in definitions — genuine accounts of the unity of some concept or property.

I have argued that cluster definitions fail as definitions, but this is of course not to argue for the stronger claim that cluster definitions fail to do any important work. I see no reason to doubt that cluster definitions contain theoretically important lists of properties and processes which are frequently used (tacitly or explicitly) as criteria for being alive. Making such lists of properties and processes explicit may ground both scientific research into the physical bases for such properties and processes, and their gathering may constitute an essential first step along the way to an adequate

can serve as criteria of life, but that does not attempt to resolve in advance all possible uncertainties about what ought to count as a living thing" (30). All page references are to Warren (1997). 24 Thus, F is defined by X, Y, and Z only if X, Y, and Z provide necessary and sufficient conditions for being F. 25 Matthews cites the 1986 edition of this encyclopedia. Upon checking the reference I am unsure that his comment reveals a charitable reading of the text. 26 Shields (1999, chapter 7) also addresses the problems with cluster definitions.

13 definition of life. What a definition must do with such clusters, however, is find a property or properties which explains the unity of these sets of properties and provides genuine necessary and sufficient conditions.

That making such clusters explicit has scientific value and value on the road to giving an account or definition of biological life is not sufficient for rendering the clusters themselves definitions. As accounts they are inherently unstable, unclear, and do not explain the phenomena they seek to unify.

1.2.1.5. Why science has not shown life to have no definition.

The retreat to cluster definitions is invoked in response to the views set out above by

Dawkins. Science, it is claimed, has shown us two things: that life is materially continuous with nonlife, and that this entails that life cannot have a 'strict' definition — there is no property shared by all and only living things. I argue in this section, however, that this retreat to the unstable weaker notion of a cluster 'definition' is unmotivated; science has not established the dual theses Dawkins invokes. Dawkins' view is composed of an empirical and a philosophical thesis; the philosophical thesis disintegrates upon examination leaving the empirical core of the thesis untouched.

It must be emphasized that the empirical thesis that life is continuous with nonlife is not challenged by my rejection of Dawkins' view.27 Rather, the important but infrequently noted problem with the view that science has proven eliminitivism about life is that it contains a false view of what material continuity entails for definability. According to Dawkins' eliminitivism, continuity of phenomena entails the absence of a real property to be defined, but this does not follow.

Intuitively, we know that in the color spectrum the colors shade indistinguishably into one another, but we also recognize that this does not mean that red is not distinct from yellow, no matter how

27 Below I suggest that the view I call here the continuity thesis does not itself constitute the empirically supported core of what science has revealed about the material continuity of living things with nonlife. This version of the continuity thesis in fact contains philosophical presuppositions concerning the ontology of the physical world which rule out possible scientifically respectable views concerning the nature of life.

14 difficult it may be to define that difference. The case that continuity fails to entail eliminitivism can be made again with a case from the philosophy of science.

Elliott Sober (1980, 166-7), arguing in response to David Hull's (1965) claim that the

Aristotelian requirement that species have essences specifiable by nontrivial necessary and sufficient conditions conflicts with material continuity, contends that essentialism can and does coexist quite peacefully with the truth of continuity theses. Sober provides an example from chemistry; there is no

'saltation'28 — no plausibly specifiable particular moment — in the transmutation of nitrogen to oxygen when the nucleus of the atom ceases to be a nitrogen nucleus and becomes the nucleus of an atom of oxygen. Nevertheless, chemical kind essentialism is widespread and defensible: nitrogen just is the chemical kind with the atomic number of 14. The continuity thesis does not undermine this position; as Sober argues: "This really does not matter, as long as the vagueness of 'nitrogen' and that of 'atomic number 14' coincide" (Sober 1980, 167).29 This example vividly illustrates the compatibility of essentialist real definitions with physically continuous processes in the area

(chemistry) where essentialism has, perhaps, its widest contemporary acceptance,30 and the same point carries over without loss to the biological case.31

The view that science has shown us the truth of eliminitivism about life rests then on a confusion between the legitimate and respectable empirically justified results of scientific research and the warrant for a peculiar (and false) view of the relation between continuity and definability.

28 To employ one of the inessentialist's favorite terms. See Dennett (1995b). 29 See also Balme's translation and notes for Aristotle's History of Animals (1991, pp. 60-1 note a and pp. 72-3 note a). See also Bedau (1992c, pp. 272-3). Polanyi (1968, 1310) gives a nice illustration of this point. Sounds I emit in speaking convey meaning. But, those sounds can be distorted by other sounds in varying degrees such that at one end of the scale, my meaning continues to be conveyed quite clearly while at the other end of the scale my utterance fails to convey its meaning since its physical carrier has been so utterly degraded. 30 Scientific essentialism's favorite examples of scientifically discoverable essences are mainly chemical in nature. 31 Chalmers (1996, pp. 53-4 & 77) contains another fruitful discussion of this point.

15 Closer attention to the philosophical aspects of life's definition reveals that science has not proven eliminitivism about life.32

1.2.1.6. Summary.

I have argued that one reason to suppose that those seeking an account of life must wait on empirical science, i.e., Artificial Life, fails. I have argued, further, that the unprecedented progress of biological science in the last century has essentially left our problem untouched for two reasons.

First, progress in biology has been in the area of detailed theoretically grounded understanding of biological structure, functioning, and evolutionary history, but the investigation of these aspects of living things proceeds on the basis of an intuitive understanding of life rather than on an explicit definition. Second, the widespread view that an eliminitivist solution to our problem follows from one of the empirically established results of modern biology — material continuity — is incorrect; material continuity is compatible with the existence of robust definitions. In this light we can see common cluster 'definitions' of life for what they are: useful lists of criteria for being alive that nevertheless fall short of offering an account of life.

A small number of philosophers, apparently recognizing these facts, have attempted to provide illuminating and scientifically respectable accounts of life. We turn now to a critical survey of such positions.

1.2.2. Philosophers on life.

While in general it seems to be true that philosophers have avoided questions concerning the nature of life,33 some have written about the problem, and indications are that more voices will be

32 Indeed, those who are historically informed may have wondered about this association from the start since Aristotle held a version of the continuity thesis and held the view that life had a definable essence. As the argument of the text shows, Aristotle's position was not based on a crude scientific error but a shrewd philosophical insight into the compatibility of these two facts. 33 Lange writes that our question "has recently been treated with benign neglect by philosophers. (It goes entirely unmentioned in current philosophy of biology texts—e.g., Rosenberg 1985, Sober 1993.)" (Lange 1996, 225). Hull and Ruse (1998) also neglect the topic; Hull (1974, ch. 5), however, does discuss life, vitalism, and mechanism. The topic receives narrow attention in Hempel (1966) and Sterelney and Griffiths (1999).

16 heard in the years to come. In this section we survey the accounts of life offered by three contemporary philosophers — Peter van Inwagen, Paul Churchland and Mark Bedau.

1.2.2.1. Van Inwagen on life.

Van Inwagen's analysis of life, offered in his book Material Beings,34 is perhaps least satisfactory of the of the three views I survey in this section. Despite this fact, van Inwagen's account is worth exploring because his attempted account of life is guided by his intuitions about the identity conditions of living things. As we will see, van Inwagen's reliance on traditional philosophical methods sets his account apart from the lion's share of contemporary work on life and places him methodologically closer to Aristotle than to other contemporary theorists.

Van Inwagen believes that it is in the end "the business of biology" to provide a full account of life (84); nevertheless, he thinks that he has 'something useful' (84) to say in response to our question, and develops his contribution in the form of a lengthy analogy. The upshot of van

Inwagen's analogical approach is that lives are reasonably well individuated, jealous, self-maintaining events.

Let us begin with the notion of a self-maintaining event;35 a storm is an example of a self- maintaining event in van Inwagen's sense. We can individuate a storm as a thing that persists over time (think of the red spot on Jupiter), but, at the same time, its composition is constantly changing: certain particles are entering and others leaving the storm constantly. Lives are like that; living things frequently ingest, digest, and slough off waste products from the materials necessary for life.

According to van Inwagen, lives are also reasonably well individuated and jealous. Lives, van

Inwagen claims, are relatively well individuated compared to flames; whereas our intuitions are no guide in telling us whether the flames of the forest fire are the same flames as the flames of the match

34 Unless otherwise noted, all page numbers and citations in this sub-section refer to the text of van Inwagen (1990). 35 There is a certain vagueness in what van Inwagen means by calling lives events which he does not clear up (see Jay Rosenberg's , criticisms); however, I will concentrate on a different problem.

17 that started it, van Inwagen is confident that lives are well individuated enough for us to know that artificially joined Siamese twins would have two lives rather than one.

The example of the artificial Siamese twins also illustrates the jealous nature of lives when taken with a new contrasting case — lives are jealous whereas waves are not. What this means is that waves can pass through each other, and when they do they share the activities of the same component molecules.

Lives on the other hand do not do this according to van Inwagen. The artificial Siamese twins do not share the same life; the activities of the simple molecules which compose the two persons are distinct activities whereas the activities of the simples which compose the two waves as they pass through each other are identical.

My objection to van Inwagen's account is not with his description of the output of his intuitions; I have a great deal of sympathy for his judgements in these cases. My problem is rather that this isn't an account of life at all, it is simply a reporting of intuitions. We know (let us agree) that lives are reasonably well individuated compared to flames, but we don't know why. We know (let us agree) that lives are jealous whereas waves are not, but not why. Van Inwagen may of course respond to this criticism by noting that it is the scientists, not the philosophers, who will eventually reveal to us why these things are true of lives, but if he applies this strategy then it is unclear what he supposes that his own account accomplishes. If traditional philosophical methods have something to contribute to our search for life's definition, then it must be more robust than this survey of features intuitively associated with being alive. Genuine analyses must do more than report on the contours of our intuitions, they must seek to root out the causes that underlie those intuitive judgements and formulate them into coherent accounts. Van Inwagen's analysis fails to do this, and for that reason fails to provide us with the account we desire.

1.2.2.2. Churchland on life.

Paul Churchland takes another tack. Where van Inwagen's account failed to systematize our intuitions, Churchland opts for systematization of phenomena at the expense of the preservation of

18 our intuitions,36 at least in his 'more penetrating' definition of life. In the philosophical background here is a common distinction between the tasks of seeking a conceptual analysis and a theoretical definition.

On a common view, conceptual analysis is conceived as an investigation into the structure and relations among the concepts we employ, while real or theoretical definition is conceived of as an investigation of actual (often scientifically revealed) nature of the entity or property that is the referent of our words and concepts in the world.37 The distinction arises from the intuitive idea that our concepts may fail to capture the way the world is; we may give a conceptual analysis of phlogiston describing the concept's meaning to theorists who employed it, but we cannot give its theoretical definition because there is no thing in the world corresponding to the concept for that real definition to capture.

Given this distinction, Churchland seeks to give a theoretical definition of life, an account that need not be acceptable to our (untrained) intuitions. Churchland offers two analyses of life in his book Matter and Consciousness, one simple and one "more penetrating" (172-3).38 The simple characterization takes self-replication to be the defining feature of life:

x is alive =df x has the capacity for self-replication. (172)

Churchland rejects this definition on the basis of the intuitive idea that while even extremely simple molecules may satisfy the analysans in certain circumstances, such molecules are not alive in those circumstances.39

36 The search for definitions that can serve as scientifically acceptable real definitions and intuitively acceptable 'conceptual analyses' is not incoherent, and Churchland's project of seeking one type of definition to the exclusion of the other may present a false dichotomy. For example, our intuition is that water and other stuffs ought to belong to chemical kinds susceptible to theoretical definition. This intuition is not undermined, then, by the scientific identification of H2O as the compositional stuff underlying water — our intuitive conception of water is in line with this scientific finding. As we will see, Aristotle believes that life has an account which is acceptable on both grounds as well. 37 Neander (1991) and Millikan (1989) discuss and employ this set of distinctions (see also Bigelow and Pargetter1987, 257). Shields (1999, chapter 3) elucidates a conception of analytic work on which these two projects come together. 38 All references in this section, unless otherwise noted, are to Churchland (1988). 39 This basis for rejecting the definition appears inconsistent with Churchland's disavowal of conceptual analysis. I comment on the point in the main text, below.

19 Churchland does think that a more penetrating definition of life can be given, however.

x is alive =df x is a semiclosed physical system and x exploits the order it already possesses and the energy flux through it in such a way as to maintain and/ or increase its internal order. (173)

Churchland notes that on this definition, beehives, termite colonies, cities, the biosphere and candle flames are all living things. If our project were the project of conceptual analysis rather than theoretical definition, these examples would constitute counterexamples to the proposed definition.

Churchland does not see them that way, however; he prefers instead to learn a lesson from these purported counterexamples.

The wiser lesson is that living systems are distinguished from nonliving systems only by degrees. There is no metaphysical gap to be bridged: only a smooth slope to be scaled, a slope measured in degrees of order and in degrees of self-regulation. (173)

Churchland thus appeals to the thesis of the material continuity of living things both as support for the idea that conceptual analyses of life will fail and as the basis for a defense of a theoretical definition that yields some counterintuitive results.

One obvious question that should be raised by Churchland's two definitions and his distinct attitudes towards them has to do with the asymmetry of his reaction to the counterexamples offered to the definitions. Counterexamples were allowed to overturn the first definition but not the second although there are no principled differences between the definitions themselves as concerns their relation to the purported counterexamples. Handling the purported counterexamples differently in the two cases thus appears ad hoc and unmotivated. Charitably interpreted, perhaps the best thing to say in Churchland's defense is that it was not the counterexamples to the first definition that drove his rejection of it at all; rather, it was the fact that a theoretically 'more penetrating' account of the phenomena of life was available, and that richer conception of life deserves top billing.

Counterexamples should (if Churchland is not simply picking and choosing among definitions in an unprincipled manner) count for nothing against either definition; theoretical biological concerns drive Churchland's search for definitions.

20 We may note further that Churchland's handling of the second definition of life appears to commit him to the view that while material continuity is compatible with theoretical definition, it is incompatible with conceptual analysis — material continuity is after all the reason we are given for not seeking conceptual analysis. We may thus propose the following revised thesis on the basis of

Churchland's response to the second definition.

CT entails the failure of conceptual analysis: There being an account of life which is intuitively acceptable is incompatible with the truth of the continuity thesis.

Unfortunately, this thesis fairs no better than the earlier thesis that the continuity thesis entails eliminitivism about life.

Just as there may be a real definition of life compatible with the truth of the continuity thesis

(see above, p. 14 ff.), so there is no incompatibility between continuity and conceptual analysis.

Thus, being bald and being hirsute are materially continuous, but we may give an intuitively acceptable analysis of the concepts: the former indicates having little or no hair whereas the latter indicates having a lot of hair. These conceptual analyses are adequate insofar as they mirror in their accounts the continuity between the things in the world. Speaking linguistically, the terms and their definitions are vague in their reference to the same cases and clear in their reference or failure of reference in the same cases and the conceptual analysis is adequate (at least in this respect). If such a conceptual analysis can be given of being bald despite material continuity, we have no reason yet to believe that life cannot be given an adequate conceptual analysis given material continuity.

Of course, Churchland may not be ruling out giving a conceptual analysis of life on the grounds of this thesis, but we should note that no other reason or indication of a reason is given for his rejection of the project. Churchland and others may of course feel themselves committed to general philosophical theses about the poverty of conceptual analysis, but the point to be made here is the simple one that those general views concerning conceptual analysis constitute a separate issue than the question of whether or not conceptual analysis is compatible with empirically confirmed material continuity. The project of giving an account of life that does justice to our intuitions about life would be undermined decisively if there were an incompatibility here, but that there is not shows

21 that narrow concerns to offer a scientifically acceptable account of life have not yet ruled out also attempting to offer an account which is at the same time acceptable to intuition.

We may thus offer the following theses.

CT plus theoretical definition: The truth of the continuity thesis is compatible with the search for a theoretical or real definition of life.

CT plus conceptual analysis: The truth of the continuity thesis is compatible with the search for a conceptual analysis of life; CT is compatible with there being an intuitively acceptable account of life.

CT plus a conceptual analysis which is a real definition: The truth of the continuity thesis is compatible with the search for a conceptual analysis of life which at the same time constitutes a scientifically acceptable real definition of the property of being alive.

Our conclusion thus far is that none of these optimistic theses concerning life's definition is undermined by narrow concerns to preserve what we know to be biological fact; the search for each type of account — or one that satisfies both simultaneously — is not undermined by biological facts.

1.2.2.3. Bedau on life.

Mark Bedau (1996) takes Churchland's idea of offering only a theoretical definition of life to a new extreme. On Bedau's approach, there are presumed to be strong enough grounds to show that all accounts sticking too close to our intuitive conception of life — whether they purport to offer theoretical or conceptual analyses of life — are bound to fail. This in Bedau's view justifies our taking a radical new approach to giving a theoretical definition of life, one only very loosely moored in what we ordinarily think of as living.

Bedau (along with his co-author for one paper, Packard), introduces the approach as follows.

What is life? How can it be recognized? In an everyday context, these questions seem tantalizingly clear—a cat is alive and a rock is not. But formalizing this distinction is difficult, especially if the formalization is to be used in empirical measurements. (Bedau and Packard1991, 457)

Because of the difficulties confronting a project to correspond to our 'tantalizingly clear' intuitive conception of life — difficulties that must be taken to be quite fatal to all such projects — Bedau and

Packard suggest a "gestalt switch" to a view of life that is "more global, statistical" in perspective.

22 So, rather than try to define what it is for an individual 'microscopic' organism to be alive, our concern is with what it is for a 'macroscopic' system (population of organisms) to exhibit the property of indefinitely ongoing life. (1991, 457)

Conceptual analysis and even theoretical definition remain too closely tied to 'life' as applied to individual organisms to succeed; the solution is to cease thinking of 'life' as applying primarily to individuals and start thinking of systems as the primary referents of 'life'.

Once we have made this 'gestalt switch' it may be possible to discover a property that will be available to empirical measurement and verification (345) and that will explain the unity of the diversity of life which we actually see (and might possibly see in AL).

The essential principle that explains the unified diversity of life seems to be this suppleness of the adaptive processes — its unending capacity to produce novel solutions to unanticipated changes in the problems of surviving, reproducing, or, more generally, flourishing. (338, cf. 333)

The essential nature of life is revealed in the property (crudely speaking) of evolving. This property is something that applies in the first instance to populations of living things rather than to individual organisms. Populations are alive in a primary sense according to Bedau, individual organisms are only alive in a derivative sense.

This last-mentioned consequence is perhaps the most striking of the counterintuitive results of Bedau's definition. Bedau is emphatic that his account of life applies in the primary instance to populations rather than individual organisms, which are only alive — in his sense — derivatively. One might plausibly object that Bedau has simply made a category mistake here: in the sense in which we were asking questions about the nature of life it is organisms that are alive in the primary sense, not populations. Any definition that implies that populations are alive in a primary sense fails as a definition of life, whatever else might be.

Of course, if this is indeed a category mistake, we must remember that it is one that is consciously chosen from a considered philosophical position.40 Bedau's reply to the above objection is simple and direct: "this objection has no force for those who are seeking the fundamental

23 explanation of the diversity of living phenomena" (340). Bedau insists that his project is not to capture our intuitions. He is not doing 'conceptual analysis' on the meanings we all have in mind when we use the term 'life', and in his view it is precisely our weddedness to this tantalizing, intuitive, yet vague and undefined conception of what it is to be alive that stands in the way of our accepting the benefits of his theoretical approach to life's nature. Thus, Bedau asserts that the counterintuitive consequences of his definition fail to count as evidence against it.

In evaluating Bedau's solution, we need to be absolutely clear that we are not calling into question the potential (although as yet largely unproven) theoretical merits of his account.41 I will offer no objection to Bedau's account that challenges the scientific value of his explication of supple adaptation.

This having been said, however, it is tempting to reply to Bedau that he does not address the original objection. To object that Bedau has not defined life, whatever else he has done, is not in conflict with supposing that what he has done is valuable in the service of other theoretically valuable projects in biology. The theoretical project that is presently at stake, however, is the definition of life, and with regards to that project it seems that Bedau's analysans is irrelevant. Let us grant that the notion of supple adaptation will prove invaluable to biology's search for unity in the diversity of life

(as ordinarily understood); even so, this fact alone is insufficient to motivate the extreme linguistic revisionism Bedau suggests when he suggests that we take 'life' now to mean his notion of supple adaptation. If Bedau is right both about the unavailability of less radical definitions of life, and also about this concept's theoretical value, then why not simply suppose that life as we understand it has

40 Although, of course, we could also give Bedau too much credit here; it must be remembered that he has offered us no reasons — theoretical, conceptual, or otherwise — to suppose that we must take the drastic 'gestalt switch' he recommends before we can have an adequate theoretical definition of life. 41 Mitchel and Forrest (1995) have this to say about the work of Bedau and Packard: "The important contribution of Bedau and Packard's paper is the attempt to define a macroscopic quantity such as evolutionary activity. It is a first step at such a definition and the particular definition of gene usage is no doubt too specific to the Strategic Bugs model, in which the relationship between genes and behavior is completely straightforward. In more realistic models it will be considerably harder to define such quantities. However, the formulation of macroscopic measures of evolution and adaptation, as well as descriptions of the microscopic

24 been eliminitively reduced from our scientific ontology and that our science has gained a new (and previously unknown) explanatory concept in supple adaptation? Nothing in Bedau's work suggests that we either need to or should accept the extreme linguistic revision he proposes.

My reply to Bedau is thus that he has elucidated a property which may be true (indirectly) of living things (as well as being true of and applying directly to non-living things) and which may be scientifically useful for various sorts of research42 without his having given us an analysis of what it is to be alive. The conceptual shift Bedau is asking us to take is simply too drastic; the fact that his account applies primarily to the wrong sorts of things is sufficient to motivate the rejection of his account as an account of life.43

The intuitive idea behind this rejection of Bedau's account is that while we do not require that our theoretical definitions capture every aspect of our intuitive understanding of everyday notions, there are some constraints on when we can legitimately say that X, Y, and Z account for A. This notion of 'this far and no further' may be explicated by distinguishing between categorial and noncategorial features of our notions.44 Thus, the number two is (intuitively) categorially an abstract object; it is not a particular thing; this is why nominalists deny that there is any such thing as a number two when they insist that all our talk about the number two can be accounted for in terms of

mechanisms by which the macroscopic quantities emerge, is essential if artificial life is to be made into an explanatory science and if it is to contribute significantly to real evolutionary biology." (275-6) 42 Cf. Bedau 1996, pp. 345-54 in this regard. 43 Faced with a similar opponent, one who stubbornly retains a definition which has been shown to fly in the face of common usage on the grounds that if common usage doesn't meet the requirements of the definition then so much the worse for common usage, Aristotle says, "one may retort to such a man that though in some things one must not speak with the vulgar, yet in a question of terminology one is bound to employ the received and traditional usage and not to upset matters of that sort" (Top. vi.10 148b16-22). Coincidentally, one of the main examples Aristotle has had in mind in his general discussion of method in Topics vi.10 is the definition of life. 44 I offer no analysis of this distinction but simply take it to be basic. The distinction nevertheless enjoys broad acceptance and use in traditional metaphysics. See chapter five for a more thorough discussion.

25 talk about particulars — they eliminitively reduce numbers out of our ontology.45 Let us formulate this idea into a constraint on adequate definitions.

The categorial constraint on proper definitions: Roughly, all definitions of F must minimally capture features of F which place it in fundamental ontological categories. While we may allow that theoretical definitions of everyday notions may fail to include every aspect of our preanalytic notion of an F, there are limits to what even a theoretical definition may revise out of our ordinary conception.

This indicates in a rough way the principle on which I reject Bedau's analysans as a definition of life. If there is no theoretical or real definition of life which captures our basic intuition that life belongs primarily to individual organisms and only derivatively (if at all) to populations, then we ought to accept eliminitivism about life's real definition.

There is, however, another response to Bedau's suggestion, and while carrying it off is much more ambitious, it employs fewer presuppositions. The response I have in mind is simply to construct a scientifically and intuitively adequate definition of life. We may show such a task to be possible by making it actual, and by doing so we will take away all plausibility to the claim that

Bedau's 'gestalt switch' about life is advisable. It is crucial to remember, after all, that while Bedau presupposes that the obstacles in the way of a definition more faithful to our everyday notion of life are extreme, he neither makes clear what those obstacles are taken to be nor offers any principled reason why the task might not be done despite the obstacles. There is a strong sense, then, in which

Bedau's gestalt switch is unmotivated, and this lends us another reason not to follow Bedau's radical linguistic revisionism.

1.2.2.4. Opposition to conceptual analysis.

None of the philosophers or biologists surveyed thus far has had ambitions to give an account of life which satisfies at the level of our intuitions.46 Much of this stems from the

45 Examples of what I mean to indicate by categorial features of our notions may be expanded easily. Ideas are categorially such that they cannot sleep or be green, but they are mental things. My chair is a physical object and not an abstract object or a mental item such as an idea. Etc. See chapter five for more on this distinction. 46 Recall that even van Inwagen, who utilized intuitions in what he had to say about life really failed to offer any theoretically unified account of life — his discussion amounted to little more than a survey of some of our

26 acceptance of a school of philosophy in which conceptual analysis is, for reasons beyond the scope of this dissertation, out of vogue.47 Adherents of this view accept the naked mind thesis:

The naked mind thesis (NM): our intuitions about x must be constantly constrained by hard empirical data concerning x if we are to make any progress in scientific (or philosophical) pursuits.48 and have taken what has been called the 'empirical turn'.49

One disturbing result of this brand of philosophical analysis that is important to note is its supposed easy victories in substantive debates. Thus, Margaret Boden (1996), objects that according to Bedau's position, creationism is analytically false. Life as Bedau defines it is only instanced by things that supply adapt (i.e. evolve), but if creationism is true, or if it could have been true, then this definition cannot be correct. Granting that scientific creationism is a deeply flawed scientific program, should our definition of life make scientific creationism analytically false?50 Is the issue not a (lopsided) scientific one? In a similar vein, someone might ask whether or not it would be true if there was a

God, or there were angels, that such beings would be alive. Such beings seem intuitively to be both

intuitions. Even van Inwagen appeared ready to appeal, in the end, to what science will eventually tell us about living things for the theoretical account which unified his intuitions about life. 47 Millikan (1989, 297) expresses a particularly vehement rejection of conceptual analysis; she claims that it is "a confused program, a philosophical chimera, a squaring of the circle, the misconceived child of a mistaken view of the nature of language and thought." The defense of this strident assessment takes the form of her positive work on the nature of language and thought, see especially (1984). Kornblith (1998) offers a less strident account of the role of intuition in naturalized philosophy. 48 The phrase derives from Dennett (1995a). For adherents and expressions of the thesis, its historical antecedents in Engels (1880/1978) and Mach (see Misak 1995, 34) and its contemporary supporters see Bedau (1992b), Dennett (1989), Kornblith (1998), Matthen (1991), Millikan (1989) and many others. 49 I borrow the phrase from Bedau (1998, 135). The so called 'empirical turn' is analogous to the linguistic turn taken by philosophers earlier in this century. As Richard Rorty notes in the introduction to his wonderful collection of essays on the linguistic turn, philosophy is marked by attempts to transform itself into science through the development of new methods. In the face of endless philosophical disagreement, philosophers of the linguistic turn tried to find objective methods by falling back to the analysis of language (Rorty 1992a; Rorty 1992b). In more recent history some philosophers, disheartened by the failure of the linguistic turn and continuing disagreement in philosophy, turn to the empirical methods of science itself to settle (what were traditionally but incorrectly thought to be) distinctively philosophical questions in metaphysics, epistemology and ethics. The 'empirical turn' is roughly equivalent to the Naturalization of philosophical thinking which heartened Daniel Dennett so in his introduction to Millikan's book (cited above). 50 On the status of 'scientific' creationism in its various current manifestations, see especially Futuyma (1983), Kitcher (1982), and, more recently, Miller (1999).

27 possible and alive,51 but again, Bedau's definition makes such intuitions analytically false because the beings are not members of evolving populations.

Bedau does not directly respond to such criticisms, but it is tolerably clear what he would say. To similar counterexamples to his definition (ex: a world in which there was and only would be one organism) he replies, "I take it that these fantasies are just that—fantasies, with no bearing on the true nature of any form of life that we could discover or synthesize" (341).52 Bedau gives such counterexamples no evidential weight; creationism is false, there are no worlds where there was and only would be one organism, and 'fantasies' about God and angels are and should remain irrelevant to science. What we want is the correct account of life as it really is in the actually obtaining world.

This response is a red herring, however. The objector notes that on this philosophical position a (lopsided) scientific debate is turned into an analytic falsehood. This point is not undermined by noting that the view in question is false and is a mere fantasy; that much may be granted by the objector. The point is that this philosophical approach achieves through theft what must be achieved through honest toil.

Further, Bedau's response rests on the undefended presupposition that intuition accommodating accounts inevitably straight-jacket science. But of course when it comes to life none

51 See Matthews (1977) for an illuminating discussion of the connections between the concepts of living and consciousness. 52 It is interesting (or, rather, puzzling) to compare Bedau's statements here with the defenses he gave of his earlier work on the nature of teleology. Considering formally identical complaints about counter-intuitive possibilities from his opponents and the suggestion that maybe getting it empirically correct was good enough, Bedau remarks that "It is true that, by accident, some systems-theoretic condition might happen to be true of all and only the actual goal-directed systems because no appropriate pseudo-goal system exists. But an appropriate pseudo-goal system might have existed and might come to exist. Therefore, any systems-theoretic condition that happened to be true for the moment would be just an accident." ( cf. also Bedau 1986, 489; Bedau 1992a, 32, emphasis added; Bedau 1992c, pp. 285-6) My sympathies lie with the answers to these objections given by the 'early Bedau' rather than the 'late Bedau'—modal intuitions are relevant in the search for adequate definitions; reading Bedau's work (late '80s & early '90s vs. mid '90s) leaves me at a loss to explain the shift in his argumentation. However, Bedau may be more sympathetic to the statement of a couple of researchers whose outlooks are in greater sympathy to his own. Langton writes, "It was only within the context of this much larger set of 'possible' chemical compounds [developed through synthesis] that researchers were able to see beyond the accidental nature of the 'natural' chemical compounds, and glimpse the regularities in the constitution of matter. To have a theory of the actual, it is necessary to understand the possible." (Langton 1995, ix-x). Karen Neander suggests that "A theoretical definition should... elucidate the theoretical role that the notion has enjoyed, and hypothetical cases can be instrumental in this respect" (Neander 1991, 324-5).

28 of our authors bothers to actually argue for this thesis. What we want is some principled reason to ground the supposed impossibility of providing a theoretically acceptable definition of life that is at the same time intuitively acceptable — a definition that would capture the conceptions of life held in common among creationists and evolutionists.

My point is simple and straightforward. An account that purports to offer a conceptual analysis of life but that also attempts to reveal the real nature of the property of being alive must pass the muster of the legitimate, empirically established conclusions of the science of life, biology. It is important to note, however, that no specific rather than perfectly general philosophical reasons to suppose that this task cannot be accomplished have been offered.53

1.2.2.5. Epistemological vs. ontological projects.

One final dimension of contemporary approaches to life deserves treatment. Recall that

Bedau and Packard motivated their 'gestalt switch' in defining life as follows:

What is life? How can it be recognized? In an everyday context, these questions seem tantalizingly clear—a cat is alive and a rock is not. But formalizing this distinction is difficult, especially if the formalization is to be used in empirical measurements. (Bedau and Packard 1991, 457)

Thomas Ray approaches the problem in the same way. He says,

Most approaches to defining life involve assembling a short list of properties of life and then testing candidates on the basis of whether or not they exhibit the properties on the list. The main problem with this approach is that there is disagreement as to what should be on the list.... I prefer to avoid the semantic argument and take a different approach to the problem of recognizing life. (Ray 1995, 180)

Mary Anne Warren, supporting cluster definitions of life, writes,

I think it best to stay with a definition similar to Webster's, i.e. one that lists characteristic features that can serve as criteria of life, but that does not attempt to resolve in advance all possible uncertainties about what ought to count as a living thing. (Warren 1997, 30)

All of these approaches to life's definition share one common assumption, the assumption that an adequate definition of life will help us resolve questions concerning so called 'borderline cases' of living things (ant colonies, self-replicating molecules, viruses—computer and otherwise, etc.).

53 See Bedau (1996, 354), Sober (1992, 375-6), Harnad (1995, 298) and Warren (1997, 26 & 30).

29 This assumption places an epistemological demand on adequate philosophical or scientific definitions. Call this requirement the decision procedure requirement.

The decision procedure requirement (DPR): A definition of X, given in terms of necessary and sufficient conditions, is adequate only if it provides us with some objective method for determining, in all cases, whether specific things are X.

The decision procedure requirement places a non-trivial requirement on definitions. DPR as applied to the case of life requires that adequate definitions given in terms of necessary and sufficient conditions yield objective decision procedures for determining, in borderline cases, whether something is alive or not.

This presupposition is highly problematic on philosophical grounds given its conflation of epistemological and ontological projects. Definitional projects as such need not be held hostage to our desire for epistemically distinct lines between the kinds of things there are in the world. No definition of being bald must provide decision procedures for determining in every case when something is and is not bald; the more natural thing to say is that if a definition of baldness did give such precise results it would for that reason fail as a definition of baldness. The analysans of baldness should follow our uncertainty about cases, it should not rule decisively on cases where the application of the term is uncertain. We may have strong pragmatic or methodological grounds for desiring clear and measurable lines between things that count as alive and those that do not, but there is no reason that the ontology of the world or our definitional practices must cooperate with our methodological and pragmatic hopes.

Acceptance of the continuity thesis, then, places no constraint on us to accept the inappropriate decision procedure requirement on adequate definitions. We can allow a correct and informative specification of a thing's essence to be epistemically indeterminate in the results it yields in borderline cases. Recognizing this we may offer a competing thesis concerning adequate definitions of life.

The No-Epistemological-Baggage Thesis (NEB): A definition of life need carry no epistemological baggage. Our definition must tell us what conditions a thing must satisfy in order to be alive;

30 however, adequate definitions of life need not yield objective decision procedures for determining in hard cases whether or not something is alive.54

The decision procedure requirement mixes legitimate metaphysical constraints on the proper analysis of a property or concept with improper epistemological constraints. The no-epistemological-baggage thesis distinguishes properly between the metaphysical tasks we legitimately expect our definitions to satisfy and improper epistemological or pragmatic concerns about the exact class of things in the world to which our definition applies. As a result, the prospects for defining life brighten considerably.55

1.2.3. Interim conclusions.

The time has come to regroup and take stock of our rather brief survey of the problem of the nature of life in contemporary philosophy and science. In addition to looking critically at a number of interesting accounts and approaches to the nature of life we have extracted and critically examined a number of theses and problems underlying contemporary work. One major point of this exercise has been simply to establish that the definition of life in contemporary philosophy and biology continues to reveal important, interesting, and unresolved philosophical problems. A second point of the exercise has been to ground the claim that there is important and interesting space for a contemporary Aristotelian account of life.

We may draw several conclusions from this brief survey. First, although the largest portion by far of contemporary work on life proceeds on the assumption that life may be given an informative account only along the lines of a theoretical definition, we have been offered no proximate reasons to suppose that respecting the legitimate results of biological science requires abandoning the project of conceptual analysis. The strongest possible argument in favor of the

54 In Paul Humphreys' words, "The slogan is: ontology first, epistemology second" (Humphreys 1995, 112). 55 It is worth recalling at this point the truth of a claim made earlier (see p. 5): the intuitive grasp biologists have on which things are living and which are not is sufficient to provide them with bountiful opportunities for fruitful study. The demise of DPR might deprive biologists and philosophers of a hope they had of gaining easy answers to previously hard questions, but biology will go on without noticing. Sterelny and Griffiths

31 compatibility of these two projects is to successfully complete it; one goal of this dissertation is to establish that Aristotle's account of life provides just such a scientifically and intuitively acceptable account.

Second, we have noted that the core scientific motivation for seeking definitions that are at best theoretical definitions stems from the acceptance of the continuity thesis (roughly, the thesis that living and nonliving things are materially continuous). But as we have seen, the truth of the continuity thesis is compatible with there being definitions that satisfy the constraints of projects of conceptual analysis, theoretical definition, or both. Further, as I will argue below, the continuity thesis as it guides contemporary work itself fails to capture the empirically established core of what we have learned from biology, for the continuity thesis itself is the conjunction of a scientifically established thesis (the thesis of the material continuity) and a mechanistic assumption about the ontology of the physical world (see below). Scientifically respectable accounts of life need not even accept the continuity thesis because of this philosophical commitment, but all accounts must accept the weaker empirical core of the thesis.

My argument in what follows is that Aristotle holds both interest and promise for his unique and subtle position on the range of issues outlined above. Aristotle is committed to the empirical core of the continuity thesis and he undertakes the ambitious project of providing an account of life that satisfies constraints from both intuition and scientific theory. Aristotle's approach to life therefore constitutes a fresh and potentially powerful contender in the burgeoning field of accounts of life and serves as a philosophically sophisticated counterbalance to contemporary accounts that operate under controversial and undefended philosophical presuppositions.

1.3. Aristotle's promise.

Given the tightly connected system of problems concerning an adequate definition of life brought to light in the previous section we may appreciate the philosophical acumen with which

comment, "we do not see how a definition of life is likely to help us with odd and hard-to-classify cases. . . . The adequacy of the definition is settled by our view of the case, not vice versa." (1999)

32 Aristotle approached our question. It is both a blessing and a curse that Aristotle's account of life is intertwined with the core of his metaphysics. It is a blessing in that it is this very feature of

Aristotle's thought that makes his contribution so rich in the philosophical resources it can bring to bear on the sorts of issues raised above. It is a curse in that obscurities in the interpretation both of

Aristotle's metaphysics and his account of life threaten to diminish the contributions his thought may make to the ongoing debate concerning the nature of life.56 My goal in this dissertation is to develop a textually supported interpretation of Aristotle's account of life.

Before moving to Aristotle's promise in this regard, however, we must allay concerns arising from Aristotle's historical associations with vitalism.

1.3.1. Was Aristotle's theory vitalistic?

Our Darwinism separates us from Aristotle so thoroughly that we must be non-Aristotelians. (Falk 1995, 311)

Aristotle is considered by at least one commentator to be a patron saint of vitalism,57 but vitalism is dead.58 My project may thus be perceived as doomed from the start. I would like to address this worry by seeking clarity about the content of a charge of vitalism.59 Given that we do not

56 It is hard not to feel some sympathy for Hobbes' famous complaint: "And indeed, that which is written there [in Aristotle's Metaphysics] is for the most part so far from the possibility of being understood, and so repugnant to natural reason, that whosoever thinketh there is anything to be understood by it, must needs think it supernatural" (1994, xlvi.14, 458). It is not unreasonable, however, to feel more optimism about Aristotle's contribution than Hobbes would allow. 57 According to Beckner (1967), "Aristotle established four traditions that, it can be said, virtually determined the course of subsequent critical vitalism: he identifies what has been called here the Life [i.e., the substantial entity which animates an organism] of an organism with its psyche; he locates the purposive activity, organic unity, and embryological development as the phenomena that vitalism must take most seriously; he argues that the activities of the part must be understood by reference to the form of the whole and that morphogenesis must be understood by reference to the form of the adult; and finally, he describes the manner of the psyche's influence on its organism as formal, not efficient, causation. In short, critical vitalism after Aristotle takes the soul as the model of the Life and attributes to Life the power of achieving and maintaining organic form." (254) 58 Beckner (1967) thinks that vitalism is irrefutable as a general thesis, but this would be bad enough for the any vitalistic theory if there were no explanatory gains to be gotten from the hypothesis. 59 I am not alone in seeking such further clarity. See also C.D. Broad, "I think one feels that the disputes between Mechanists and Vitalists are unsatisfactory for two reasons. (i) One is never quite sure what is meant

33 want to be vitalists, why do we want not to be vitalists? Just what is contained in the charge that a theory a theory of life's nature is or is not vitalistic, and what makes such charges stick? Why is the charge of vitalism fatal to the theory against which it is justly raised?

1.3.1.1. What is vitalism?

Vitalism is best introduced with reference to the rival thesis of mechanism. Ernst Mayr distinguishes usefully between two distinct versions of a mechanist view of life. Strong mechanists claim that organisms are 'nothing but' machines, "the workings of which can be explained by the laws of mechanics, physics, and chemistry" (1982, 51). However, Mayr notes that contemporary mechanists modify this view "rather drastically." The contemporary mechanist accepts that:

there is nothing in the processes, functions, and activities of living organisms that is in conflict with or outside of any of the laws of physics and chemistry.... [But] they do not accept... that animals are 'nothing but' machines.... The phenomena of life have a much broader scope than the relatively simple phenomena dealt with by physics and chemistry. (Mayr 1982, 52)60

Building on this account, we may distinguish between strong and weak mechanisms as follows.

Strong mechanism: Organisms are nothing but chemical machines — all their properties and parts are wholly reductively identifiable with and explicable in terms of the laws of physics and chemistry as they apply outside of living systems.

Weak mechanism: Organisms are 'something more' than chemical machines; although their activities do not conflict with the laws of physics and chemistry, at least some of their properties or parts

by 'Mechanism' and by 'Vitalism'; and one suspects that both names cover a multitude of theories which the protagonists have never distinguished and put clearly before themselves. And (ii) one wonders whether the question ought to have been raised long before the level of life.... The question: Is chemical behaviour ultimately different from dynamical behaviour? seems just as reasonable as the question: Is vital behaviour ultimately different from non-vital behaviour" (1925, pp. 43-4). Carl Hempel says, "the issue can be fruitfully discussed only if the meaning of the opposing claims can be made sufficiently clear to show what sorts of argument and evidence can have a bearing on the problem and how the controversy might be settled" (1966, 101). 60 Building on Broad's account (1925, 45-6), McLaughlin gives this definition of Comprehensive Mechanism: "What we may call 'Comprehensive Mechanism' holds if and only if the following four conditions are met. First, every object is or is entirely made up of elementary material particles. Second, the force-generating properties are possessed by (at least) some kinds of elementary material particles. Third, the value of any force-generating property of a whole is determined, in accordance with a compositional principle, by the values of that sort of property for at least some of its parts. Fourth, forces combine by a principle of vector addition; such principles are themselves compositional principles: the value of the force exerted by a whole is determined in accordance with such a principle by the value of that force as it is exerted by the components of the whole." (McLaughlin 1992, 77) As McLaughlin notes, this version of mechanism is false if compositional principles employ nonlinear functions (77n36). However, certain contemporary mechanists appear to want to use the modeling of such nonlinear functions in explanations their explanations, see for example Bedau (1997).

34 are not wholly reductively identifiable with or explicable in terms of the laws of physics and chemistry as they apply outside of living systems.

It is worth pausing over these definitions for a moment before moving on to elucidate corresponding vitalistic doctrines.

The point that concerns me here is to note that Mayr's definition of contemporary or weak mechanism is fully compatible with that paradigm of nonphysicalist doctrines, Cartesian dualism. No

Cartesian dualist about the mind must claim that mental interactions are in conflict with laws of physics (rather than compatible with them when fully understood), nor must she affirm that minds are outside the influence of physical and chemical laws. As we will see below (in the appendix to chapter six), distinguishing between the physical and the nonphysical is an incredibly thorny job, surprisingly difficult to complete successfully without simply resorting to stipulative definitions.61

Mayr's failure to exclude such paradigm nonphysicalist views as Cartesian dualism in his account of mechanism (!) is just one indication of the thorniness of the philosophical problems we are approaching, and this should put us on guard against any too hasty judgements against a theory for supposed 'vitalistic' contamination. Capturing the set of distinctions that interests us in this area of physical ontology is no easy matter.

Moving ahead, just as Mayr distinguishes between crude and sophisticated mechanism, so we may distinguish between two forms of vitalism. Mayr labels as "extreme vitalism," the view that organisms are "completely controlled by a sensitive if not thinking soul" (1982, 114). This seems to suggest a view in which living things are governed entirely by souls or entelechys to the exclusion of material or physical causes and explanations. On extreme vitalism, we can expect laws of nature to be broken and overridden.

Mayr also speaks of much less radical views as belonging to the "vitalistic school."

Distinguishing the defining characteristics of this 'sophisticated' vitalism requires a bit of work.

According to Mayr, these vitalists believe "that there are processes in living organisms which do not

61 Or sophisticated moves which amount to mere stipulation.

35 obey the laws of physics and chemistry" (Mayr 1982, 52). According to a recent encyclopedia of philosophy, "Vitalism holds that living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things" (Bechtel and Richardson 1998, 639). Carl Hempel writes,

According to neovitalism, [the teleological characteristics of living things] do not occur in nonliving systems and cannot be explained by means of the concepts and laws of physics and chemistry alone; rather, they are manifestations of underlying teleological agencies of a nonphysical kind, referred to as entelechies or vital forces. Their specific mode of action is usually assumed not to violate the principles of physics and chemistry, but to direct the organic processes, within the range of possibilities left open by the physico-chemical laws, in such a way that, even in the presence of disturbing factors, embryos develop into normal individuals, and adult organisms are maintained in, or returned to, a properly functioning state. (1966, 71)62

Elliot Sober adds a condition on vitalism such that vitalists maintain, while mechanists (or physicalists) deny that "two objects could be physically identical even though one of them is alive while the other is not" (2000, 23-4).

While there is some discrepancy between these statements, the consistent theme of this weaker sense of vitalism is that vital forces are (in some sense) independent of physical laws. This independence is either explained by vital forces' ability to break physical laws (as in strong vitalism), or a claim to the effect that vital forces fail to depend for their existence upon the purely physical interactions of the physical parts of organisms (weak vitalism). If this is correct, we may distinguish between two vitalistic theses.

Strong vitalism: That property or entity in virtue of which living things are alive is (i) irreducibly distinct from its physical properties and parts, (ii) to some extent determines the course of physical events in living things, and (iii) breaks or overrides physical laws in the course of (ii).

Weak vitalism: That property or entity in virtue of which living things are alive is (i) irreducibly distinct from its physical properties and parts, (ii) to some extent determines the course of physical events in living things, and (iii) fails to depend for its existence on the interactions of such physical parts of living things as there may be.

62 According to Hempel, the problem with positing such entities from a scientific standpoint is that such a posit is not "definite enough to permit the derivation of specific implications concerning the phenomena that the theory is to explain.... [A]ll that the neovitalist doctrine enables us to do is to make the post factum pronouncement: 'There is another manifestation of vital forces!'; it offers us no grounds for saying 'On the basis of the theoretical assumptions, this is just what was to be expected—the theory explains it!'" (1966, 72)

36 With these definitions in hand we are in a position to understand why, given contemporary scientific knowledge, it is unacceptable to be a vitalist.

1.3.1.2. How vitalism was refuted.

The progress of biology in the last century has seen the advent of methods and theories sufficiently robust to make any claims that physical laws are broken in living things implausible as well as undermining any plausibility even for the weaker claim that living things somehow fail to depend on their physical parts for their being alive. This dissertation accepts in no uncertain terms that it is a condition of adequacy on any theory of the nature of life that one respect these results and the unifying explanatory role63 that Darwin's theory of evolution has provided to our understanding of living things.64 Vitalism in both its strong and weak forms, then, is well and truly dead, and we can appreciate the grounds for this judgement.

1.3.1.3. Are mechanism and vitalism the only alternatives?

Nevertheless, we can see why it is that the terms 'mechanism' and 'vitalism' are slippery; each thesis shades off into theses which have not been empirically refuted and remain live options. Thus, plausible property dualisms maintain that the mental depends for its existence (at least in cases with

63 In Dobzhansky's famous words, "Nothing in biology makes sense except in the light of evolution" (Dobzhansky 1973). Mayr notes, "Perhaps the most impressive aspect of current biology is its unification. Virtually all the great controversies of former centuries have been resolved" (Mayr 1982, 131). Ruse (following Whewell) argues that the theory of evolution is 'the best kind of science' in that it brings many disparate areas of inquiry under on principle: the principle both illuminates the sub-disciplines and the sub-disciplines combine to give credence to the principle. "Convergence on a common principle convinces us that we have moved beyond coincidence" (Ruse 1998, cf. esp. pp. 2-4). Kitcher says, "When we look at the last 120 years of the history of biology, it is impossible to ignore the fecundity of Darwin's ideas. Not only have inquiries into the presuppositions of Darwinian histories yielded new theoretical disciplines (like population genetics), but the problem-solving strategies have been extended to cover phenomena that initially appeared troublesome.... The comparison [with Newton's physics] is apt.... In both cases, we find a unified theory whose problem-solving strategies are applied to illuminate a host of diverse phenomena. Both theories offer problem solutions that can be subjected to rigorous independent checks. Both open up new lines of inquiry and have a history of surmounting apparent obstacles. The virtues of successful science are clearly in display in both.... Evolutionary theory is not simply an area of science that has had some success at solving problems. It has unified biology and has inspired important biological disciplines." (Kitcher 1982, 53-4) 64 According to Mayr, it was the recognition "that all manifestations of development and life are controlled by genetic programs" (Mayr 1982, 106) that finally put an end to any controversy between vitalism and (crude) mechanism. As Boyce Rensenberg says, "modern biology confirms the view that all the phenomena that together constitute life can be understood in terms of chemistry and physics" (Rensberger 1996, 21).

37 which we are most familiar) on the physical and interacts with the physical without breaking any physical laws.65 Given this, such property dualisms avoid vitalistic charges on the account given above.66 By the same token, however, property dualism is compatible with a commitment to the formulation of weak mechanism given above, and indeed most property dualists would endorse weak mechanism as stated.

Of course, the fact that property dualism is compatible with this form of weak mechanism establishes nothing substantive about its acceptability as a thesis in the philosophy of mind; my point here is rather that it shows something important about defining vitalism and mechanism. If we are to capture the distinction between property dualisms, vitalisms, and mechanisms, then we need to draw finer grained distinctions between our concepts.

I approach this issue by strengthening our definition of weak mechanism so that it rules out at least some nonepiphenomenalist versions of property dualism.67 How we choose to precisify the definition of weak mechanism, above, such that it excludes at least strong nonepiphenomenalist versions of property dualism without collapsing back into strong mechanism is a technical decision.68

I choose the following precisification.69

Sophisticated mechanism: (i) living things are wholly composed of physical parts; (ii) some parts or properties of living things are not reductively identifiable with underlying physical parts and properties but are reductively explicable in those terms; and (iii) no property not reductively

65 Perhaps along the lines suggested by Hempel's remarks, quoted above, perhaps in other ways. 66 They avoid this trivially, of course, because they are not meant as accounts of the property in virtue of which things live. The point is simply that the ontological conditions stated in vitalistic theories that make it plausible to suppose that vitalism has been scientifically refuted do not likewise make it plausible to suppose that property dualism along the lines indicated above has been scientifically refuted. 67 I choose this option instead of the option of weakening a definition of vitalism so that strong nonepiphenomenalist versions of property dualism satisfy its definition because I believe there are strong constraints on the contemporary usage of 'vitalism' to the effect that vitalism, whatever it is, must have been shown empirically false by the progress of biology in the twentieth century. But, property dualism has not been shown false by the progress of biology in the twentieth century, and so property dualism is not a form of vitalism, and it would be misleading to characterize it as such. Best to follow the intentions of property dualists and seek to find a 'middle way' between Cartesian dualisms and strict physicalism. 68 Cf. Horgan (1994, 471 & 474). 69 I defend the terms in which this definition is framed in the appendix to chapter six of this dissertation.

38 identifiable with underlying physical parts or properties has 'its own' causal powers; the causal powers of organisms are exhausted by the causal powers of their physical parts.

Such a definition allows us to distinguish a 'middle way' between mechanists and vitalists, and allows us to deny that property dualists are mechanists despite the fact that they accept weak mechanism.

This 'middle way' is occupied by emergentist accounts of life and mind.

Emergentist accounts: (i) living things are wholly composed of physical parts; (ii) all parts and properties of living things are causally or logically dependent for their existence on the interactions of their physical microparts; (iii) not every part or property of living things is a part or property fully reductively identifiable with the parts and relations of those same materials outside of living things; and (iv) the 'emergent' parts or properties noted in (iii) exert 'their own' causal influence over the course of their microparts' careers without breaking laws governing the behavior of microparts and properties.

As I have drawn these definitions, the crux of this issue between sophisticated mechanists and emergentists has to do with the problem of 'downward' causation.70

Both sides of the debate between sophisticated mechanists and emergentists accept upward determination. Both sides accept, that is, that higher level properties and parts of organisms, whether reducible to their physical bases or not, depend for their existence on micro properties and parts and their activities. Both sophisticated mechanists and emergentists accept, in addition, that there are no activities in embodied living beings which break physical law. Emergentism and vitalisms accept, but sophisticated and strong mechanisms reject, downward causation.

1.3.1.4. Was Aristotle a vitalist?

We must now return from these conceptual issues and bring our results to bear on the question of Aristotle's supposed commitment to vitalism. I accept that vitalism is a theory that has suffered empirical refutation in the twentieth century; thus, if Aristotle endorses a vitalistic account of life then his account has been falsified and cannot offer an adequate contemporary account of life.

While I cannot argue the claims in sufficient depth here (see further chapter seven), I will outline the

70 'Downward causation' is typically contrasted with 'upward determination'. Water's properties (liquidity, etc.) are thought to be determined in an 'upward' fashion by the properties of water's micro-parts. Whether there are any genuine instances of 'downward' causation where 'high level' properties of wholes influence the course of micro-events is a vexed issue which I discuss in depth in chapter six of this dissertation.

39 case for the plausible view that Aristotle was committed not to vitalism but to some form of emergentism.

The case proceeds as follows. Aristotle accepts both the irreducibility and the downward causal efficacy of certain forms (see Phys. i.6 189a28-33, GA ii.4 738b19-26; see also GA i.20 729a9-

14, i.21 729b6-21, iv.1 765b10-15); he is therefore no strong or sophisticated mechanist. Further, he accepts upward determination (see GC i.10 327b23-7, DA i.5 409b28-8); he is therefore no strong vitalist. Aristotle accepts that downward causation breaks no lower level material laws (see GA v.8

789a8-b8, 789b1-15, APo. ii.11 94b28); he is therefore no weak vitalist. Aristotle appears, then, to be an emergentist weak mechanist.

If this hypothesis is correct, then we have an understanding both of why Aristotle's view has been taken to be vitalist and of why it is that his account may nevertheless constitute a scientifically acceptable approach on the contemporary scene. Confusion about Aristotle's status as a vitalist or a mechanist comes from insufficient attention to the complex metaphysical differences between the views; sloppy accounts of mechanism or vitalism fail to capture the distinctive senses of either thesis.

Aristotle's approach holds contemporary promise, moreover, because contemporary accounts of life proceed on the philosophical — not scientific — assumption of sophisticated mechanism. Nothing about the progress of science has shown emergentism false; indeed, we have positive evidence from contemporary science that some form of emergentist ontology obtains in the actual world.71

1.3.2. Aristotle and material continuity.

Aristotle's approach rejects the philosophical presuppositions of contemporary accounts of life in another scientifically acceptable and philosophically astute way. This comes to light through noting that Aristotle seems to have held a surprisingly modern version of a continuity thesis while rejecting what is today almost universally assumed to be a consequence of that view. Aristotle tells us that,

71 These claims are argued below in chapter six of this dissertation.

40 Nature passes from lifeless objects to animals in such unbroken sequence, interposing between them beings which live and yet are not animals, that scarcely any difference seems to exist between two neighboring groups owing to their close proximity. (PA iv.5 681a11-15)72

Nature proceeds little by little from things lifeless to animal life in such a way that it is impossible to determine the exact line of demarcation, nor on which side thereof an intermediate form should lie. Thus, next after lifeless things comes the plant, and of plants one will differ from another as to its amount of apparent vitality; and, in a word, the whole genus of plants, whilst it is devoid of life as compared with an animal, is endowed with life as compared with other corporeal entities. Indeed, as we just remarked, there is observed in plants a continuous scale of ascent towards the animal. So, in the sea, there are certain objects concerning which one would be at a loss to determine whether they be animal or vegetable. For instance, certain of these objects are fairly rooted, and in several cases perish if detached; thus the pinna is rooted to a particular spot, and the razor-shell cannot survive withdrawal from its burrow. Indeed, broadly speaking, the entire genus of testaceans have a resemblance to vegetables, if they be contrasted with such animals as are capable of progression. In regard to sensibility, some animals give no indication whatsoever of it, whilst others indicate it but indistinctly. Further, the substance of some of these intermediate creatures is fleshlike, as is the case with the so-called ascidians and the sea-anemones; but the sponge is in every respect like a vegetable. And so throughout the entire animal scale there is a graduated differentiation in amount of vitality and in capacity for motion. (HA viii.1 588b4-23; see also OH i, 279a29)

It may appear from these selections that Aristotle held a straightforward version of the continuity thesis as expressed above (see p. 10).

This supposition runs into trouble, however, given that Aristotle fails to endorse the type of account of life offered by contemporary nonsceptics concerning life's definition. Note that the continuity thesis (as stated) is compatible only with mechanist accounts of life.73 I have formulated the theses along these lines to reflect the fact that, for a number of philosophical reasons to be explored in this dissertation,74 contemporary theorists have exclusively defended strong or sophisticated mechanist accounts of life. Expressions of the continuity thesis have been framed exclusively in these terms in contemporary debate as a result.

If we supposed that the only options in giving an account of life were vitalist accounts

(strong or weak) and mechanist accounts (strong or sophisticated), then we would be justified,

72 Unless otherwise noted, all translations are from those in the Revised Oxford Translation (ROT) edited by John Barnes (1984). 73 While the current formulation of the continuity thesis rules out sophisticated mechanism, a weaker version of the continuity thesis could be formulated compatible with contemporary work on the nature of life. 74 See chapters five and six of this dissertation for in depth treatment of modern philosophical and scientific approaches to the methodological and ontological concerns that drive a wedge between Aristotelian and modern approaches to our problem.

41 perhaps, in making this association between the continuity thesis and mechanist accounts of life given the refutation of vitalism by contemporary biological investigation. Given the availability in logical space of emergentist accounts of life, however, there is interesting and scientifically respectable territory left to be occupied given the acceptance of the empirical core of continuity thesis. Two main burdens of this dissertation consist in establishing that Aristotle filled at least a part of this unoccupied logical space75 and that such a view is not only a respectable contender on the contemporary scene but has much to recommend it.76

The same strains in Aristotle's thought which lead interpreters to attribute vitalistic or emergentist positions to Aristotle force us to deny that he held the modern version of the continuity thesis defined above (see p. 10). But, History of Animals viii.1 588b4-23 and Parts of Animals PA iv.5

681a11-15 establish that Aristotle held the empirical core of the continuity thesis. We may formulate this core as follows:

The thesis of material continuity (TMC): Living things are materially continuous with nonliving things, in the sense that at the borderline of the two classes they fade indistinguishably into one another.

This thesis constitutes the empirically supported core of the continuity thesis, and, unlike the continuity thesis (as formulated above) makes no commitment to strong or sophisticated mechanism.

This general formulation of a continuity thesis makes no commitments to philosophical claims concerning the compatibility or incompatibility of material continuity with the existence of irreducible properties possessing novel causal influence, and it is this weaker continuity thesis that science has established and which we should attribute to Aristotle.

75 The bulk of this dissertation is devoted to establishing this thesis; see especially chapters two through four and chapter seven. 76 See especially the arguments of chapters five and six.

42 1.3.3. Theoretical or conceptual definition?

Given that Aristotle will be no sceptic concerning the account of life, we may wonder whether the account he offers will attempt an adequate conceptual analysis or be in the form of a theoretical definition — or whether his account will attempt to supply both.

Aristotle's commitments in terms of both philosophical and scientific methodology strongly suggest that he does not support any strong version of the naked mind thesis (see above, p. 27).

Aristotle's statements concerning scientific methodology all declare that he is liberal, if judicious, in the types of evidence he is willing to countenance in theory construction.77 At times he allows empirical observation to over-ride common sense beliefs78 while at other times he allows common- sense and intuition to assert themselves over theories that are too far removed from the facts.79 If these positions are correct, then there is support for the claim that at least part of Aristotle's goal in offering a definition of life will be to capture the core commitments of the everyday notion of being

77 In my view Aristotle accepts intuition (nous) as a necessary component of any satisfactory epistemology. This view is heavily embattled in contemporary literature on Aristotle's epistemology: see Lesher (1973), Hamlyn (1976), Burnyeat (1981), and Engerg-Pedersen (1979). Irwin (1988) supports the position for Aristotle's early works, but denies it for Aristotle's later philosophical works. I argue that Irwin does not establish this switch on either textual or philosophical grounds in Cameron (1998). This is not the place, however, to defend Aristotle's epistemological commitments in greater detail. For purposes of this dissertation Aristotle's commitment to dialectic as a way to first principles in science is sufficient to ground my claims (see Top. i.2 101a25-b4). 78 See in this regard especially Aristotle's comments on which opinions it is necessary to examine in ethical and dialectical contexts. Here are a couple of examples: "Dialectic does not construct its deductions out of any haphazard materials, such as the fancies of crazy people, but out of materials that call for discussion" (Rhet. i 1356b35) and "Educated men lay down broad general principles; uneducated men argue from common knowledge and draw obvious conclusions. We must not, therefore, start from any and every opinion, but only from those of definite groups of people — our judges or those whose authority they recognize" (Rhet. ii 1395b30; cf. also Rhet. ii. 12-14 for a description of the typical character traits of a young man, an old man, and a man in his prime, as well as 105a3, 1094b27 ff., 1095a28, 1096a9, 1179b25, 1214b29 ff., 1217a9, 1364b12 ff., 1394b7, etc.) 79 Theories are 'too abstract' when they are too far removed from the principles or phenomena at hand (GA ii. 747b29; cf. 698a13, 748a8, & 1235a2). See Meteorology i.13 for an 'ingenious' scientific account that is 'plainly false' and compared to which the 'unscientific account' is better. Note also, "If the axiom is relevant but too implausible, the answerer, while admitting that if it is granted the conclusion sought follows, should yet protest that the proposition is too silly" (Top. viii 160a6) and "the argument of Melissus is gross and offers no difficulty at all: accept one ridiculous proposition and the rest follows — a simple enough proceeding" (Phys. i 185a10; also 193a4 ff., 1218b22, 1006a5, 1217a9, & 163b13).

43 alive (see Met. ii.1 993a27-b8, etc.) even while he seeks a theoretically sound scientific and philosophical position on the subject.

Whether or not life has an account satisfactory to philosophically and scientifically informed common sense is discovered only through formulating and testing such accounts. Aristotle criticizes the theories of previous thinkers (see especially his criticism of Dionysius' definition of life in Topics vi 10, 148a23 ff.) but does not despair of giving a philosophically and scientifically adequate definition of life—instead he offers one (which requires a great deal of unpacking) at de Anima ii.4

415b13.

Further, regardless of one's position on intuition and the role of 'conceptual analysis' either in Aristotle or in contemporary philosophy, Aristotle's procedure of attempting to offer a satisfactory analysis of life is certainly not misguided at this point. No theorist we have investigated80 has offered any reason other than the thesis of material continuity (and, perhaps implicitly, the perceived failures of past attempts) to believe that a definition of life that satisfies both our everyday intuitions and legitimate scientific constraints cannot be given. We have already seen, indeed, that the thesis of the material continuity of living things — the empirical core of the continuity thesis — while true gives no support for the claim that life has no intuitively plausible definition.81 In the absence of such a principled reason, surely the attempt to satisfy the strong demands of such an account has both philosophical and scientific interest.

It is plausible, then, to suppose that Aristotle sees no conflict between the goals of arriving at a considered theoretical position which also meets constraints set by our everyday notions

80 See Bedau (1991, 457), Sober (1992, 375-6), Warren (1997, 26), and Harnad (1995, 298) quoted above. 81 We do, after all, find the essentialist account of chemical kinds in terms of their atomic numbers highly intuitively satisfying given that our intuitions indicate that these are compositional kinds whose natures will be revealed to us, if at all, not through a priori investigation but through empirical research.

44 concerning life. Aristotle would appear to seek both a conceptual analysis and a theoretical definition of life.82

1.3.4. Section summary.

In this section I have argued that Aristotle's view on life holds contemporary interest and promise for a number of complementary reasons. Aristotle's view is plausibly construed as unrefuted by the scientific evidence that succeeds in refuting vitalism, yet Aristotle's view is unique on the contemporary scene for offering a nonmechanistic account of life. If this is Aristotle's position, then he occupies an intrinsically interesting and currently unoccupied location in the space of possible accounts of life. Further, Aristotle's acceptance of the empirical core of the continuity thesis without its philosophical presupposition of mechanism displays another respect in which Aristotle is unique, sound, and sharp in his philosophical commitments. Finally, Aristotle's project is ambitious and interesting in that he promises to provide an account of life that is both scientifically and intuitively acceptable, bucking the contemporary trend to abandon without argument the attempt to satisfy intuitional constraints.

1.4. Conclusion.

Our brief survey of the contemporary literature on the nature of life has revealed an area of investigation rich in substantive philosophical and scientific problems remaining to be resolved.

Furthermore, while a number of distinctive positions in logical space have been filled by contemporary theorists, it remains the case that positions that hold both philosophical and scientific promise have not yet received a developed treatment.

82 This view is argued to be a pervasive feature of Aristotle's philosophical and scientific approach by Shields (1999).

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