FROM CONCEIVABILITY TO POSSIBILITY An Essay in Modal Epistemology Anders Berglund UMEÅ STUDIES IN PHILOSOPHY 8 FROM CONCEIVABILITY TO POSSIBILITY An Essay in Modal Epistemology Anders Berglund Umeå 2005 © Anders Berglund 2005 Series editors: Gunnar Andersson, Ingvar Johansson, and Sten Lindström Department of Philosophy and Linguistics Umeå University SE-901 87 Umeå, Sweden ISBN 91-7305-861-0 ISSN 1650-1748 Printed in Sweden by NRA Repro AB, Umeå 2005 Distributor: Department of Philosophy and Linguistics, Umeå University, SE-901 87 Umeå, Sweden. Persistence ABSTRACT This study deals with the thesis that conceivability implies possibility. Confronted with alleged counterexamples to this thesis, some philosophers have turned to what may be called “idealized” or “more demanding” notions of conceivability. I argue that in turning to such notions, they have made the thesis useless to limited beings like us for attaining modal knowledge. However, in refusing to identify conceivability with demanding or idealized notions, we cannot maintain that conceivability always implies possibility. Essentially, there are two ways to proceed: to view conceivability as a mere guide to possibility, or to argue that the conceivability thesis is a local truth, i.e., a truth with respect to a certain class of statements. I defend the latter alternative. This class of statements employs concepts with respect to which doubt concerning the conceivability thesis is to be regarded as general skepticism, not as skepticism relating to the conceivability thesis itself. I proceed by outlining an interpretation of strict possibility—i.e., the kind of possibility that I take the conceivability thesis to be about—according to which modal truths depend essentially on conceptual relations, as opposed to obtaining purely in virtue of properties of things themselves. Given this account, on which both ideal conceivability and strict possibility have a conceptual ground, I argue that these notions are not only coextensional but relate to one and the same property of statements. I further argue that the impossible is unimaginable, but that it is conceivable in the sense that one can misdescribe the contents of imagination. Key words: Conceivability, conceivability arguments, possibility, modal epistemology, modal metaphysics, Descartes, Arnauld, Chalmers, Kripke, Yablo. ACKNOWLEDGEMENTS Central parts of the present thesis are based on my talk “What does it mean that something is conceivable?” held at Filosofidagarna in Stockholm, June 15, 2001. I want to thank everybody who came to listen to my talk and who contributed to the ensuing discussion. I also want to thank Peter Nilsson for valuable comments on drafts of that talk. Philosophically, three persons have influenced me more than others. First, I want to thank Daniel Svensson. Our early discussions kindled much of the passion that enabled me to see this project through. Secondly, I want to thank Professor Joseph Almog, whose lectures and seminars have been a continuing source of inspiration. Thirdly, and foremost, I want to thank my supervisor Professor Sten Lindström for the many sessions at the blackboard and for his unswerving patience and support. I also want to thank everybody at the Department of Philosophy and Linguistics, Umeå University. In particular, Peter Melander, Jonas Nilsson, Pär Sundström, and Peter Nilsson have provided fruitful criticism, which in many cases has led to substantial revisions. I also want to thank Per Nilsson and Anders Odenstedt for continuous support. Anders deserves special thanks for stylistic revisions of the text. The main financial support for this work has been provided within the framework of the research project “Medvetande, Materialism och Möjlighet” (“Mind, Materialism, and Modality”) financed by The Bank of Sweden Tercentenary Foundation. On a personal note, I want to thank my son David, my parents Anita and Kennet, my sister Frida, and Monica for their support. I also want to thank the members of Umeå Kendo Club, especially Stefan Sandström. This thesis is dedicated to David. TABLE OF CONTENTS 1. MODAL EPISTEMOLOGY 1 1.1 Two introductory questions...................................... 1 1.2 Modal facts................................................... 2 1.3 Modal statements.............................................. 6 1.4 Modal statements and modal arguments.......................... 10 1.5 Preview of the thesis........................................... 15 2. THE SOURCES OF MODAL KNOWLEDGE 23 2.1 Can we discover the truth-values of modal statements?............. 24 2.2 How can we discover the truth-values of modal statements?......... 25 2.3 Modal knowledge based on logical and conceptual analysis ......... 27 2.4 Modal knowledge based on intuition ............................. 30 2.5 “Basic” modal knowledge ...................................... 34 2.6 Imagination and modal knowledge............................... 37 2.7 Conceivability and modal knowledge ............................ 43 3. THE CONCEIVABILITY THESIS 47 3.1 The conceivability thesis and its proponents....................... 47 3.2 What should we take it to mean that something is conceivable? ...... 51 3.3 What should we take “implies” to mean? ......................... 53 3.4 What kind of possibility shall we take the conceivability thesis to attribute to conceivable things?................................. 56 4. CONCEIVABILITY ARGUMENTS IN THE PHILOSOPHY OF MIND 61 4.1 Introduction .................................................. 61 4.2 Descartes’ mind-body argument and Arnauld’s criticism ............ 62 4.3 Is there a limit to Arnauldian skepticism?......................... 76 4.4 Contemporary mind-body arguments............................. 78 4.5 Summary.................................................... 88 5. INTERPRETATIONS OF CONCEIVABILITY 91 xii From Conceivability to Possibility 5.1 Introduction .................................................. 91 5.2 Absolute and relative notions of conceivability .................... 97 5.3 Distinctions concerning the way in which something is conceived . 104 5.4 Genuine and apparent conceivability ............................ 114 5.5 What should we take it to mean that something is conceivable? ..... 126 6. MODALITY 135 6.1 Introduction ................................................. 135 6.2 Broad logical modality........................................ 137 6.3 Metaphysical modality........................................ 140 6.4 Rigid designation and “sameness”.............................. 145 6.5 Essentialism, conceptualism, or skepticism?...................... 149 6.6 Summary and discussion...................................... 159 7. CONCLUSIONS AND DISCUSSION 163 7.1 Introduction ................................................. 163 7.2 The conceivability thesis as a local truth ......................... 169 7.3 A broader perspective......................................... 171 7.4 Outlines of a modal epistemology .............................. 179 BIBLIOGRAPHY 187 SUBJECT INDEX 195 CHAPTER 1 MODAL EPISTEMOLOGY 1.1 Two introductory questions This is a thesis in modal epistemology. The qualifying term ‘modal’ is meant to indicate that modal epistemology is a special branch of epistemology. More familiar branches of epistemology are, for example, the epistemology of mathematics and the epistemology of empirical knowledge. Whereas the epistemology of mathematics and the epistemology of empirical knowledge are concerned with the questions if, and how, mathematical and empirical knowledge can be obtained, modal epistemology is concerned with the question if, and how, knowledge about what is possible and what is necessary can be obtained.1 The following questions, which I have adopted from van Inwagen (1998: 74), with some terminological changes, are central in modal epistemology: (1) How can we know that a statement S (say, “Water ≠ H2O”) is possible, or possibly true, when we either know that S is false (which is the case for “Water ≠ H2O”) or when we do not know whether S is true or false?2 (2) How can we know that a statement S, which we know to be true, is also necessarily true? All the problems that I intend to raise and discuss in this thesis are in one way or another derived from these questions. As they stand, the questions (1) and (2) involve a number of presuppositions. One implicit assumption is that modal statements are either true or false, and accordingly, that there is something that makes them true or false. Another assumption is that the notion of a statement is intelligible. In this introductory chapter, I shall spell out the presuppositions involved in the questions above, 1 The term ‘modal epistemology’ is used by several authors as a name of this topic. See for example Yablo 1993, van Inwagen 1998, and Casullo 2000. 2 In what follows, I shall take “… is possible” and “… is possibly true” to be synonyms. I shall also take “… is necessary” and “… is necessarily true” to be synonyms. 2 From Conceivability to Possibility and I shall explicate the various terms employed. In section 1.2, I shall discuss the notion of a modal fact, and the idea that there are modal facts. In section 1.3, I provide a first characterization of modal statements in connection to the previous discussion concerning modal facts. The explications made in sections 1.2 and 1.3 will provide a more clear demarcation of the topic of this thesis. In section 1.4, I discuss the use of modal statements in philosophical arguments. Finally, in section 1.5,