Modality and Explanatory Reasoning Modality and Explanatory Reasoning Boris Kment 1 1 Great Clarendon Street, Oxford, ox2 6dp, United Kingdom Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries © Boris Kment 2014 The moral rights of the author have been asserted First Edition published in 2014 Impression: 1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by licence or under terms agreed with the appropriate reprographics rights organization. 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Meiner Familie Acknowledgements I am indebted to many philosophers for their comments on various bits and pieces of this material, including Simona Aimar, Ralf Bader, David Baker, Gordon Belot, Karen Bennett, Daniel Berntson, John Burgess, Jeremy Butterfield, David Chalmers, Shamik Dasgupta, Cian Dorr, Antony Eagle, Dorothy Edgington, Andy Egan, Adam Elga, Delia Graff Fara, Michael Fara, Graeme Forbes, Laura Franklin-Hall, Anil Gupta, Ned Hall, Elizabeth Harman, Gilbert Harman, Christopher Hill, Harold Hodes, Thomas Hofweber, Mark Johnston, James Joyce, Thomas Kelly, Philip Kremer, Igal Kvart, Marc Lange, Stephan Leuenberger, Eric Lormand, William Lycan, David Manley, Michael McKinley, John Morison, Sam Liao, Martin Lin, Vivek Matthew, Ram Neta, Howard Nye, Laurie Paul, David Plunkett, Jim Pryor, Peter Railton, Agustín Rayo, Nicholas Rescher, Gideon Rosen, Geoffrey Sayre-McCord, Jonathan Schaffer, Kieran Setiya, Ted Sider, Scott Soames, Sharon Street, Jamie Tappenden, Dimitris Tsementzis, Jason Turner, Ted “Fritz” Warfield, Brian Weatherson, Bruno Whittle, to the anonymous ref- erees of the book manuscript, as well as to the audiences of talks I gave at Princeton, Cornell, Pittsburgh, the University of Michigan at Ann Arbor, the University of North Carolina at Chapel Hill, Notre Dame, MIT, Victoria University in Wellington, the Australian National University, the Arizona Ontology Conference 2009, the University of Colorado at Boulder, and the Princeton Paper Tigers, to the participants of graduate seminars I taught at the University of Michigan and Princeton University, and to those attending the Corridor Philosophy Workshop sessions where ancestors of Chapters 4 and 6 were discussed. Special thanks are due to Christopher Hill for his copious and spectacularly detailed and helpful comments. I am grateful to Simona Aimar and Antony Eagle for organizing a discussion group about the book manuscript at Oxford University, to the members of that group for coming up with helpful com- ments and suggestions, and to Simona Aimar and Vivek Matthew for collecting some of this feedback and sending it to me. Many thanks are due to Daniel Berntson and Dimitris Tsementzis for astute comments and help with editing the manuscript. I am grateful to Dorothy Edgington from whom I have learned a lot about counterfactual conditionals. My greatest debt is to Gideon Rosen and Mark Johnston for their philo- sophical insights and their support and encouragement while advising my doctoral dissertation, of which some parts of this book are distant descendants. I am grateful to Mind for permission to use material from my paper “Counterfactuals and Explanation” (vol. 115, 2006, pp. 261–310), to Philosophical Perspectives for per- mission to use material from “Counterfactuals and the Analysis of Necessity” (vol. 20, 2006, pp. 237–302), and to Nous for permission to use material from “Causation: Determination and Difference-Making” (vol. 44, 2010, pp. 80–111). Research for this book was assisted by a Charles A. Ryskamp Fellowship from the viii Acknowledgements American Council of Learned Societies during the academic year of 2011–2012. I am grateful for their support. I am equally indebted to the National Endowment for the Humanities for fellowship support (Grant Number FA-54195-08) during the academic year 2008–2009. (Any views, findings, conclusions or recommendations expressed in this book may not reflect those of the National Endowment for the Humanities.) Finally, I am grateful to Princeton University for a preceptorship that allowed me to be on leave and devote myself fully to research during the academic year of 2013–2014. Contents 1. Synopsis 1 1.1 The Nature of Modality 2 1.2 Modality and Explanation 5 1.2.1 Explanation 5 1.2.2 The Direction of Analysis 6 1.2.3 Closeness to Actuality 8 1.3 The Function of Modal Thought 10 1.4 Modality in Metaphysics 14 1.5 The Question of Reduction 15 1.6 A Guide for Selective Readers 18 2. The Nature of Modality 20 2.1 Necessity as Invariability 21 2.1.1 The Problem of the Narrow Circle 21 2.1.2 Truth in a Situation 22 2.1.3 Ramseyfying out of the Circle 26 2.2 Necessity as Unconditional Truth 27 2.3 Necessity as Secure Truth 28 2.4 The Necessity Scale 30 2.5 Modal Holism 34 2.6 Comparisons 37 2.6.1 Modality and the Space of Worlds 37 2.6.2 Modal Monism and Modal Dualism 38 2.7 An Agenda for the Analysis of Modality 43 Appendix A 46 Appendix B 51 3. Absolute Necessity and Iterated Modality 54 3.1 Context Dependence and the Absolute Nature of Necessity 54 3.1.1 Absolute Terms 54 3.1.2 Context Invariance and the Quest for Precision 59 3.1.3 Other Domain Restrictions 60 3.2 Worlds and Possibility 61 3.3 Modal Operators and Iterated Modality 63 3.3.1 Modal Operators 63 3.3.2 The Tetradic Relation of Comparative Closeness 65 3.3.3 The Modal Status of Modal Truths 67