THE CATHOLIC UNIVERSITY OF AMERICA Hylomorphism and Diachronic Identity: A Thomistic Approach A DISSERTATION Submitted to the Faculty of the School of Philosophy Of The Catholic University of America In Partial Fulfillment of the Requirements For the Degree Doctor of Philosophy © Copyright All Rights Reserved By Patrick Joseph Rooney Washington, D.C. 2017 Hylomorphism and Diachronic Identity: A Thomistic Approach Patrick Joseph Rooney, Ph.D. Director: Michael Gorman, Ph.D. Philosophers have struggled to agree on a satisfactory theory of diachronic identity, or identity through time. There are two opposing families of theories, perdurantism and endurantism, each with its shortcomings. Perdurantism, on the one hand, defends many claims that appear to conflict with prephilosophical views of change and substance-feature relations. For instance, most perdurantists argue that change is not a matter of the same object having and then losing a feature; rather, change amounts to the successive existence of various “temporal parts” of the object, some of which have the feature, some of which do not. Endurantism, on the other hand, claims to defend a commonsense view of change and identity. However, endurantists struggle to provide a coherent account of the central notion of their theory, the “whole presence” of a persisting object through change. This dissertation outlines and defends an endurantist theory that overcomes the shortcomings of previous theories of diachronic identity. This theory, hylomorphic endurantism (HE), builds on the Aristotelian ontology of Thomas Aquinas. Unlike other theories, it accounts for the identity of individual substances in terms of the identity of two ontological constituents: substantial form and matter. In drawing on Thomistic ontology for principles of identity, HE solves the main problems of perdurantism and previous versions of endurantism. In contrast to perdurantism, HE defends a view of change in which a single individual directly possesses the features that it gains and loses. HE also articulates exactly how an individual can be wholly present through changes that are numerous and profound. In addition to showing how HE can address well-known puzzles about diachronic identity, I argue that the theory offers solutions to unexplored but important puzzles about self-change. In this phenomenon, an individual causes a change in itself. The ability of some individuals to change seemingly essential features is paradoxical; it suggests that an individual possesses the ability to make itself an essentially different kind of being. By demonstrating how radical self-change is possible without essential change, HE resolves this paradox. This dissertation by Patrick Rooney fulfills the dissertation requirement for the doctoral degree in Philosophy approved by Michael Gorman, Ph.D., as Director, and by Gregory Doolan, Ph.D., and Kevin White, Ph.D., as Readers. ___________________________ Michael Gorman, Ph.D., Director _____________________________ Gregory Doolan, Ph.D., Reader _____________________________ Kevin White, Ph.D., Reader ii CONTENTS Acknowledgments ..................................................................................................................... v Introduction ............................................................................................................................... 1 Chapter 1: What a Theory of Diachronic Identity Must Do ..................................................... 8 Scope of the Inquiry ...................................................................................................................................... 9 Problems about Diachronic Identity ........................................................................................................ 11 Indiscernibility of Identicals ....................................................................................................................... 11 The Problem of Temporary Intrinsics ...................................................................................................... 15 The Problem of Material Constitution ..................................................................................................... 18 Self-Change ................................................................................................................................................... 20 Explanatory Power ...................................................................................................................................... 34 Conclusion .................................................................................................................................................... 44 Chapter 2: Current Theories of Diachronic Identity and Their Shortcomings ...................... 45 The Fundamental Distinction .................................................................................................................... 45 Perdurantism ................................................................................................................................................ 50 Endurantism ................................................................................................................................................. 54 Varieties of Perdurantism ........................................................................................................................... 63 Varieties of Endurantism ............................................................................................................................ 67 Perdurantism’s Implausible Conclusions ................................................................................................. 72 Endurantism’s Lack of Explanatory Power ............................................................................................. 79 Conclusion .................................................................................................................................................... 87 Chapter 3: Diachronic Identity in Thomas Aquinas ............................................................... 89 A Different Theory ...................................................................................................................................... 89 The Basics: Substance, Form, and Matter ................................................................................................ 93 More Thomistic Metaphysics: Esse, Accidents, and Properties ........................................................ 109 Thomas on Identity .................................................................................................................................. 114 Thomas as a Proto-Endurantist .............................................................................................................. 114 The Principles of Identity ........................................................................................................................ 120 How Form and Matter Are Principles of Identity ............................................................................... 126 Rival Interpretations of Thomas ............................................................................................................ 141 iii Substantial Form as the Sole Principle of Identity............................................................................... 141 Esse as the Principle of Identity ............................................................................................................. 148 Conclusion ................................................................................................................................................. 158 Chapter 4: The Problems of Diachronic Identity Resolved .................................................. 160 Ontological Explanation in HE .............................................................................................................. 161 Whole Presence Explained ...................................................................................................................... 168 Leibniz’s Law Reframed .......................................................................................................................... 175 The Problem of Temporary Intrinsics Neutralized ............................................................................. 181 The Problem of Material Constitution Solved ..................................................................................... 189 Taking Stock .............................................................................................................................................. 209 Chapter 5: Identity through Self-Change—HE on Embryonic Development ...................... 211 Thomas’s Theory of Embryological Development ............................................................................. 213 Thomas’s View of Development in Relation to Diachronic Identity ............................................... 226 Objections to the Thomistic View and Similar Viewpoints ............................................................... 238 Developing a Hylomorphic Alternative: A Deeper Understanding of Potentiality ........................ 244 Final Remarks ............................................................................................................................................ 253 Conclusion ............................................................................................................................. 255