1 The Empirical Relevance of Metaphysics by David Builes B.S. Mathematics, B.A. Philosophy Duke University, 2016 SUBMITTED TO THE DEPARTMENT OF LINGUISTICS AND PHILOSOPHY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY MAY 2020 ©2020 Massachusetts Institute of Technology All rights reserved Signature of Author……………………………………………………………………………….... Certified by ………………………………………………………………………………………... Bradford Skow Laurance S. Rockefeller Professor of Philosophy Dissertation Supervisor Accepted by………………………………………………………………………………………... Bradford Skow Laurance S. Rockefeller Professor of Philosophy Chair of the Committee on Graduate Students 2 The Empirical Relevance of Metaphysics by David Builes Submitted to the Department of Linguistics and Philosophy on May 22, 2020 in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Philosophy Abstract Are metaphysical debates relevant to ordinary empirical inquiry? This dissertation collects a series of papers which answers in the affirmative. The first part of the dissertation is concerned with inductive inference. I argue that we shouldn’t expect the world to be amenable to induction if orthodox versions of Humeanism or Non-Humeanism are correct. I then develop and defend a hybrid view, a ‘Humean Non-Humeanism’, which has a better hope of vindicating inductive inference. The second part of the dissertation is concerned with self-locating belief. While puzzles regarding self-locating belief are often motivated by certain fanciful thought experiments, it has recently been argued that the epistemology of self-locating belief is of central concern to many of the deepest questions in fundamental physics: including the interpretation of quantum mechanics, large-scale cosmology, and the (alleged) fine-tuning of the universe. I begin by arguing that the correct epistemology of self-locating belief is also relevant to classic debates in the metaphysics of time. By exploiting the fact that different theories in the metaphysics of time classify different sorts of facts as ‘merely indexical’ facts, it can be shown that different views in the metaphysics of time make different empirical predictions. I then turn to argue for the correct epistemology of self-locating belief on metaphysical grounds. I first argue for some conditional claims: if one holds certain (controversial) metaphysical views regarding the nature of objects, properties, and identity across time, then one should uphold a particular theory of self-locating belief. I then go on to argue for an overall metaphysical picture that vindicates these views concerning the nature of objects, properties, and identity across time. Dissertation Committee Bradford Skow (Chair), Laurance S. Rockefeller Professor of Philosophy Roger White, Professor of Philosophy Miriam Schoenfield, Associate Professor of Philosophy Jack Spencer, Associate Professor of Philosophy 3 Table of Contents Front Matter Acknowledgements 4 Preface 5 The Empirical Relevance of Metaphysics Part One 6 1. A Humean Non-Humeanism 7-38 2. The Ineffability of Induction 39-66 Part Two 67 3. Self-Locating Evidence and the Metaphysics of Time 68-85 4. Time-Slice Rationality and Self-Locating Belief 86-108 5. No-Self Location 109-137 6. The World Just Is The Way It Is 138-168 4 Acknowledgements MIT has been a wonderful place to pursue my philosophical interests over the past few years. I would like to thank everyone in the MIT community for making the department so welcoming and supportive. For giving me helpful feedback on the ideas present in this dissertation, thanks go to David Balcarras, Tyler Brooke-Wilson, Alex Byrne, Kevin Dorst, Caspar Hare, Sally Haslanger, Michele Odisseas Impagnatiello, Agustín Rayo, Haley Schilling, Alex Skiles, Robert Stalnaker, and Stephen Yablo. Special thanks go to my committee members – Miriam Schoenfield, Brad Skow, Jack Spencer, and Roger White. Many of the philosophical views that I have pursued at MIT are very speculative and counterintuitive. Having a committee that has encouraged me to explore these ideas, while at the same time exposing me to all sorts of different criticisms (both in style and substance), has been invaluable. For those who helped me on a more personal level during my time at MIT, special thanks goes to David Balcarras, Allison Balin, Nathaniel Baron-Schmitt, Tyler Brooke-Wilson, Thomas Byrne, Shannon Doberneck, Kevin Dorst, Kelly Gaus, Kat Hintikka, Michele Odisseas Impagnatiello, Daniel Muñoz, Haley Schilling, Miriam Schoenfield, Ginger Schultheis, Jack Spencer, and Kirsi Teppo. Lastly, thanks to my family for providing me the opportunities and support for pursuing my passions. 5 Preface Metaphysics has always been particularly vulnerable to skeptics. The notions that metaphysicians work with (e.g. possibility, fundamentality, existence) are so basic that it’s hard to elucidate them in more basic terms. Many philosophers profess to not even understand the central questions of metaphysics. Those who do understand the questions give wildly incompatible answers, with no consensus in sight. Moreover, given that rival metaphysical views are often ‘empirically equivalent’, it’s very unclear what the correct methodology for metaphysics is supposed to be. How are we supposed to tell if atoms-arranged-table-wise compose a table or not? As a practicing metaphysician, I have often wrestled with these doubts. One of the primary aims of this dissertation is to try to respond to these doubts. If it can be shown that metaphysical debates regarding modality (chapter 2), casual powers (chapter 2), time (chapter 3), persistence (chapter 4), mereology and ontological categories (chapter 5), etc. should be taken to have observable, empirical consequences, then not even the most hardcore logical positivist should be skeptical of these debates. If this claim can be substantiated, it would also reveal a new methodological approach to metaphysics. If different views in (say) the metaphysics of modality have empirical consequences (chapter 2), then we may be able to get purely empirical evidence into the nature of modal space, just as we get empirical evidence for ordinary scientific theories. A second aim of this dissertation is purely epistemological. Formal epistemologists have done a lot of work in justifying various purely formal constraints on epistemic rationality, such as probabilism and conditionalization. However, these purely formal constraints aren’t much help in scientific theorizing. Merely having probabilistic credences isn’t going to make you a good scientist. Perhaps the central epistemological task with respect to science consists in trying to solve the so-called problem of induction. Why are the inductive inferences that scientists make rational? In the first part of my dissertation, I argue for the negative point that orthodox Humean and Non- Humean views cannot justify induction (chapter 2). I also develop and defend an alternative metaphysical picture that may have the resources to justify induction (chapters 1 and 2). The positive proposal I offer is in many ways incomplete however, and I hope to flesh out the details in future work. Another exciting area in epistemology with relevance to science is the problem of self-locating belief. Some of the deepest questions in contemporary fundamental physics - concerning the correct interpretation of quantum theory, the apparent fine-tuning of the universe, and the large- scale cosmological structure of the universe - may (surprisingly) all turn on the correct theory of self-locating belief! In the second part of my dissertation, I try to derive the correct theory of self- locating belief from metaphysical principles (chapters 4-6). 6 PART ONE The Problem of Induction 7 Chapter 1: A Humean Non-Humeanism The world is an astonishingly regular place. Apples fall, planes fly, and bread nourishes. The astonishment only increases when one looks at fundamental physics. Fundamental physical entities always seem to behave according to certain elegant, ironclad, mathematically precise rules. This is utterly baffling. Why should this be so? Standard answers to this question are usually divided into two camps: Humean accounts and non- Humean accounts. Both camps are driven by different core commitments, and as a result, Humeans and non-Humeans end up with very different metaphysical pictures. The goal of this chapter is to provide a synthesis of Humean and non-Humean views, which seeks to accommodate the core commitments of both views. My first task will be to say something about what these core commitments amount to. I do this by briefly going over orthodox Humean and non-Humean views, together with the main objections each side makes to the other (sections 1 and 2). I then go on to develop the corresponding synthesis in three stages. First, I argue that any such synthesis is committed to a specific view regarding the source of causal power in the world (sections 3 and 4). Second, I argue that any such synthesis is committed to a particular view in the metaphysics of persistence (section 5). Third, I argue that any such synthesis is committed to a particular view concerning the mereological structure of the world (section 6). Lastly, I argue that none of the objections canvassed in sections 1 and 2 have any force against the resulting synthesis (section 7). Before we begin, some caveats are in order. Since my goal is to synthesize two very general metaphysical pictures, the Humean picture and