Mere Possibilities METAPHYSICAL FOUNDATIONS OF MODAL SEMANTICS Robert Stalnaker Mere Possibilities METAPHYSICAL FOUNDATIONS OF MODAL SEMANTICS Robert Stalnaker It seems reasonable to believe that there might have existed things other than those that in fact exist, or have existed. But how should we understand such claims? Standard semantic theories exploit the Leibnizian metaphor of a set of all possible worlds: a proposition might or must be true if it is true in some or all possible worlds. The actualist, who believes that nothing exists except what actually exists, prefers to talk of possible states of the world, or of ways that a world might be. But even the actualist still faces the problem of explaining what we are talking about when we talk about the domains of other possible worlds. In Mere Possibilities, Robert Stalnaker develops a framework for clarifying this problem, and explores a num­ ber of actualist strategies for solving it. Some philosophers have hypothesized a realm of individual essences that stand as proxies for all merely possible beings. Others have argued that we are committed to the { Mere Possibilities} Carl G. Hempel Lecture Series { Mere Possibilities} Metaphysical Foundations of Modal Semantics Robert Stalnaker Princeton University Press Princeton and Oxford Copyright © 2012 by Princeton University Press Published by Princeton University Press. 41 William Street. Princeton. New Jersey 08540 In the United Kingdom: Princeton University Press. 6 Oxford Street. Woodstock. Oxfordshire 0X20 ITW press.princeton.edu All Rights Reserved ISBN 978-0-691-14712-3 Library of Congress Control Number: 2011939335 British Library Cataloging-in-Publication Data is available This book has been composed in Minion Pro with Bauer Bodoni Std. 2 Display Black Printed on acid-free paper. ~ Printed in the United States of America 10987654321 To my students, who have taught me so much philosophy, among other things. {Contents} Preface ix 1 On What There Isn't (But Might Have Been) 1 2 Merely Possible Possible Worlds 22 3 What Is Haecceitism, and Is It True? 52 4 Disentangling Semantics from Metaphysics 89 5 Modal Realism, Modal Rationalism, Modal Naturalism 126 Appendix A Modeling Contingently Existing Propositions 136 Appendix B Propositional Functions and Properties 139 Apl)endix (: A Model for a Mighty Language 149 vii viii CONTENTS App(~ndix I) Counterpart Semantics for the Cheap Haecceitist 154 References 157 Index 161 {Preface} I have been thinking about possible worlds and making use of the apparatus of possible-worlds semantics since I took a semi­ nar taught by Saul Kripke in my last year of graduate school at Princeton in 1964-65. In my early work that used that framework, on the semantics for conditionals, the representation of proposi­ tional content, and the dynamics of discourse, I didn't worry much about the metaphysical questions-about what possible worlds and merely possible individuals are, and whether it is legitimate to take them seriously. The idea seemed clarifying, and the semantic framework seemed to yield results, and that was good enough for one who prided himself on his lack of an ontological conscience. But I was puzzled (and ultimately chastened) by a remark by Larry Powers in an insightful commentary on an early paper of mine on propositions: "The whole idea of possible worlds (perhaps laid out in space like raisins in a pudding) seems ludicrous:'l At the time, it had not occurred to me that one might think of possible worlds as parallel universes, but I came to see that if one is to reject this literal-minded interpretation of the term (which I soon learned was defended by David Lewis), one needs to say something about what these things are. I tried to do this in a paper, "Possible Worlds;' first published in 1976, but that paper is silent about a further question about merely possible individuals: How, on an actualist interpreta­ tion of possible worlds as ways a world might be, is one to account for the possibility that there be individuals other than those that actually exist? That is the main focus of this book. I Powers 1976, 95. ix x PREFACE Responding to the problem led me into a tangle of metaphysi­ cal issues. I have always been a reluctant metaphysician-one who acknowledges that metaphysical questions cannot be avoided but who continues to be puzzled about their nature. While my pri­ mary aim in this book is to say something about the substantive questions of modal metaphysics, I also have a secondary aim: to get clearer about metaphilosophical questions about the nature of metaphysics and about the relation between semantic and sub­ stantive philosophical questions. For the most part, I don't address the. meta-questions directly in the book. The best way to approach them, I think, is to focus on first-order metaphysical questions, keeping an eye, and occasionally commenting, on what one is doing as one is doing it. While I have, and express in the book, a substantive view about the metaphysics of mere possibilities, I also try to develop a com­ mon framework for representing alternative metaphysical pictures and to make as coherent as I can the metaphysical pictures that I ultimately want to reject. I think this helps clarify, by contrast, the picture I want to defend, but it also tends to sharpen the puzzle­ ment about the nature of metaphysical theses. How do we choose between formally coherent alternative metaphysical theories? I don't have a complete answer to this question to offer, but I hope what I say will be relevant to it. This project began with an informal talk, some years ago, to the Arche group at the University of St. Andrews. The talk grew into a paper that eventually became chapter 1 of this book. Chapter 2 overlaps with a second talk given at a conference on modality at St. Andrews and published in the proceedings of that conference.2 The invitation to give the Hempel lectures at Princeton University pro­ vided the occasion for further development of the ideas. The first three chapters were based on those lectures, given in May 2009. A 2 Stalnaker 2009. PREFACE xi month later I gave the Pufendorf lectures at the University of Lund, adding a fourth lecture to those given at Princeton. An expansion of this lecture became chapter 4. I am grateful to Arche and the philosophy departments at Princeton and Lund for giving me the opportunity to develop and present these ideas and to the audi­ ences at these occasions for stimulating and helpful discussion. Thanks to Agustin Rayo, Bob Hale, and Damien Rochford, who read a complete draft of the manuscript and gave me very helpful comments that led to what I hope are improvements. Thanks to Aviv Hoffmann and Delia Fara for discussion and comments. Thanks to my editor, Rob Tempio, for his support and advice. Thanks also to an anonymous referee for Princeton University Press, who gave me insightful comments that led to significant revisions. For editorial help at the late stage of preparation of the manuscript, thanks to copy editor Jennifer Backer and Damien Rochford. I was particularly pleased to have the opportunity to give lec­ tures that honored C. G. Hempel, who was my teacher and super­ visor at Princeton, as well as a philosopher whose writings helped draw me into philosophy years before I came to know him. He has long been a role model for me for his clarity of mind, his generosity, and his integrity. The audience for the lectures at Princeton that honored one of my teachers included two others who had been among my graduate teachers at Princeton, Paul Benacerraf and Gil Harman, still hang­ ing around the place more than forty years later. It also included four philosophers I had taught, former students in the graduate program at MIT who are now on the faculty at Princeton: Adam Elga, Delia Fara, Liz Harman, and Sarah McGrath. The occasion led me to reflect on the relationship between graduate students and their teachers. I felt like a link in a chain that goes back to the heyday of logical empiricism and forward long into the future. I learned a lot and was profoundly influenced by my undergradu­ ate and graduate teachers, but when I became a teacher myself I xii PREFACE learned that the impact goes the other way as well. Interaction with a really excellent group of graduate students in philosophy at MIT over the twenty-three years I have been there has challenged and inspired me, helped keep me open to new ideas, and influenced the direction of my work. I take pride in their accomplishments, but mainly I want to thank them for their contributions to my under­ standing of philosophy. This book is dedicated to those students and former students. Cambridge, MA January 2011 { Mere Possibilities} { t } On What There Isn't (But Might Have Been) The problem of ontology, Quine told us in his classic essay "On what there is;'l can be put in a simple question, "what is there?" and answered in a word: "everything:' My question should be equally simple, and its answer should follow from Quine's: there is noth­ ing that isn't. But of course as Quine went on to say, the problem gets harder when one tries to be more specific about what there is and what there isn't. Quine's concern was mainly with the prob­ lem of expressing disagreement about ontology-if I believe there are more things in Heaven and Earth than are dreamt of in your philosophy, how can you talk about what it is that I believe in, but you do not? But even when we agree about what there is, we may want to acknowledge that things might have been different-:not just that things might have been differently arranged but that there might have been different things than there actually are.