Problems for Modal Reductionism: Concrete Possible Worlds as a Test Case Jonathan Nassim Thesis submitted for the degree of Doctor of Philosophy Birkbeck, University of London I hereby declare that the work contained in this thesis is entirely my own. Jonathan Nassim 2 Abstract This thesis is an argument for the view that there are problems for Modal Reductionism, the thesis that modality can satisfactorily be defined in non-modal terms. I proceed via a case study of David Lewis’s theory of concrete possible worlds. This theory is commonly regarded as the best and most influential candidate reductive theory of modality. Based on a detailed examination of its ontology, analysis and justification, I conclude that it does badly with respect to the following four minimal conditions on a satisfactory reductive theory of modality: that it be (a) genuinely reductive, (b) materially adequate, (c) conceptually adequate and (d) that its justification provides good reason to think it true. These problems for Lewis’s theory are not, I suggest, due to his idiosyncratic conception of possible worlds as concrete entities. Rather, because Lewis’s theory can be seen to represent an important class of structurally similar reductive theories of modality, the problems for Lewis’s theory generalise to problems for these other theories. This suggests that Modal Reductionism is unpromising. In the light of this, the alternative approach to understanding modality, Modal Primitivism, appears more attractive. 3 This thesis is dedicated to my family 4 Acknowledgements I would like to thank a number of people who have helped me complete this thesis. My supervisors, Ian Rumfitt and Keith Hossack, have been very generous with their time, and it is through many stimulating discussions with them that the ideas and the shape of this thesis took form. I found myself lucky to be in a department with such a rich tradition of thinking about modality. In particular, the depth and clarity of Ian McFetridge’s writings on this topic (and others) both inspired and provided a daunting standard to live up to. I also wish to thank Birkbeck College and the Royal Institute of Philosophy’s Jacobsen Studentship for the funding that enabled me to write this thesis. My friends at Birkbeck have been supportive in many ways. I thank in particular Robert Bassett whose insightful comments, questions and lessons have left their mark throughout this thesis. Robert, together with Christoph Schuringa, Adam Ferner, Alex Douglas, Dan Adams, Chris Sykes, Nathan Hauthaler and Michael Coughin have read, commented on and discussed my work, and it has hugely improved thanks to their help. There are many others who kindly offered their help and I also thank them. Long before Birkbeck, Marie McGinn, my first philosophy tutor, offered me the time, patience and a supportive space to ask questions without feeling stupid; and her guidance as to how they shouldn’t be answered still informs my thinking. Later, Ralph Walker’s generosity and belief I could think for myself are gifts I still treasure. More recently, it was attending the lectures and seminars of Saleh Agha and Patrick Lewtas, together with many discussions with them in the American University of Beirut, which rekindled my interest in philosophy and led me to begin this thesis. Finally, I want to thank my councilor and friend, Charles Hampton, whose kindness and gentle words have guided me through dark times and light. It is hard to express what I owe to my family and how grateful I am for them. The love of my brother, David, and mother, Joan, have given me the knowledge that if I fall, I will be caught; and my late father, Victor, still teaches me what it is to persevere. I want lastly to thank my beloved partner Mikala for among other things, helping to give structure to a structureless thesis, commenting on several chapters, and discussing its subject-matter with me (ad nauseam) over several years, and generally putting up with me. But she has given me so much more, and it is for that I want mainly to thank her. 5 The music-master praised the bird tremendously, and insisted that it was much better than the real nightingale, not only as regarded the outside with all the diamonds, but the inside too. ‘Because you see, my ladies and gentlemen, and the emperor before all, in the real nightingale you never know what you will hear, but in the artificial one everything is decided beforehand! So it is, and so it must remain, it can’t be otherwise. You can account for things, you can open it and show the human ingenuity in arranging the waltzes, how they go, and how one note follows upon another!’ (Hans Christen Anderson, ‘The Nightingale’) And now the question remains whether we would give up our language-game which rests on ‘imponderable evidence’ and frequently leads to uncertainty, if it were possible to exchange it for a more exact one which by and large would have similar consequences. For instance, we could work with a mechanical ‘lie detector’ and redefine a lie as that which causes a deflection on the lie detector. So the question is: would we change our way of living, if this or that were provided for us? – And how could I answer that? (Ludwig Wittgenstein, in Kerr 2008, 91) 6 Contents Chapter 1: Introduction 1.0 Modal Reductionism...………………………………………………….... 9 1.1 Concrete possible worlds as a test case………………………...………… 19 1.2 Testing reductive theories of modality…………………………………… 26 1.3 Thesis outline…………………………………………………………….. 33 Chapter 2: Lewis’s theory of modality 2.0 Lewis’s theory of modality………………………………………………. 36 2.1 Relating Lewis’s ontology of worlds and the analysis of modality……… 39 2.2 Justification………………………………………………………………. 49 Chapter 3: Ontology 3.0 Introduction…………………………………………………………….… 56 3.1 Why Lewis needs a principle of plenitude………………….……………. 57 3.2 Ways…………………………………………………………….………... 60 3.3 The objection to Ways………………………………………………......... 65 3.4 The Principle of Recombination and its roles in Lewis’s theory………… 68 3.5 Objections to The Principle of Recombination..….……………………… 71 3.51 Irreducible modality…………………………………………….… 72 3.52 Material inadequacy………………………………………….…… 75 3.6 Assessment…………………………………………………….…………. 85 Chapter 4: Analysis 4.0 Introduction………………………………………………………………. 87 4.1 Lewis’s analysis is a conceptual analysis..………………………..……… 93 4.2 Lewis’s arguments for the conceptual connection……………………….. 100 4.21 Translation with explicit rules……………………………………. 101 4.22 Clarification and critique…………………………………………. 102 4.23 Translation without explicit rules………………………………… 109 4.24 Clarification and critique…………………………………………. 111 4.25 The Theoretical Identification Argument………………………… 120 7 4.26 Clarification and critique…………………………………………. 121 4.3 Arguments against the conceptual connection……………….…………... 129 4.31 Quantification and understanding………………….……………... 130 4.32 Ontological commitments and modal concepts…………………... 137 4.4 Assessment…………………………………………….………………..... 145 Chapter 5: Justification 5.0 Introduction………………………………………………………………. 147 5.1 Lewis’s conception of primitives………………………………………… 153 5.2 The Modal Reduction Principle and The General Reduction Principle….. 156 5.3 The Unification Principle and The Truth Principle……………………..... 162 5.4 Objections to Lewis’s justification…………………………….…………. 168 5.5 Assessment……………………………………………….………............. 183 Chapter 6: Conclusion 6.0 Results of the case study………..………………………………………... 185 6.1 Generalisations and their limitations…………………….………….......... 187 6.2 Modal Primitivism………………………………….…………………….. 201 Bibliography……………………………………………………...…………. 207 8 Chapter 1: Introduction 1.0 Modal Reductionism I Modal notions play a fundamental role in our lives and thought. Without them there is much we could not think or do. The connections between modality and the standard accounts of decision-making, free will and moral responsibility, abundantly illustrate this. On such accounts, decision-making involves deliberation about which of a range of possible actions should be performed, and the selection of one to perform.1 Free will places a modal condition on decision-making: having a free will requires being free to choose to do a possible action, say F. We are free to choose to do F only if we could have chosen to do another possible action G. Finally, moral responsibility requires free will, for we are not morally responsible for actions with respect to which we couldn’t have chosen otherwise. So modality comes into standard accounts of: (a) what we reason about when we deliberate, (b) what we aim to bring about when we act, (c) free will, and so (d) moral responsibility. These connections suggest a rather platonic picture of humans: their rational minds can escape this earthly realm, and gain access to the paradise of possibility. In this realm an array of possible actions are contemplated and one selected to bring about by action. This platonic picture is supported by a long tradition which seeks to distinguish humans from other animals by virtue of our access to the realm of possibility, and the use we make of it in our lives. Often our access to it is tied to our linguistic capacities. For instance, Pettit holds that it is certainly unlikely that non-human animals live up to the picture [of decision-making as a matter of deliberation+decision]. According to this description, the options over which agents deliberate are abstracta, not concreta: they are ways things might be – ways the agent knows how to make things be – not actual events. Human beings can identify such entities on the