Humean Metaphysics and the Philosophy of Science Callum James Duguid Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Philosophy, Religion and the History of Science June 2017 - ii - - iii - The candidate confirms that the work submitted is his own and that appropriate credit has been given where reference has been made to the work of others. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. The right of Callum Duguid to be identified as Author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. © 2017 The University of Leeds and Callum Duguid - iv - Acknowledgements As with any project of this nature, the completion of this thesis was only possible due to the support that I have received from numerous people. The department at Leeds has been a consistently supportive place to work over the last few years, and I would like to thank the philosophers and historians who have made it that way. I have been helped in many ways by my fellow postgraduates, far too many in fact to mention here! I would like to offer particular thanks to Victor Dura-Vila, Simon Hewitt, Scott Shalkowski, Pekka Väyrynen and Paolo Santorio for having me lecture on their modules and for giving me good advice on the practice of teaching. Thanks to Adrian Wilson for his encouragement and for putting a metaphorical gun to my head. Thanks also to Juha Saatsi, both for pushing me towards doing better philosophy and for reminding me to focus on what matters. I owe a huge debt of gratitude to my supervisor, Steven French. His constant support and patience in helping me develop some truly sketchy ideas into rather more plausible claims will not be forgotten. In addition to these intellectual contributions, I have also benefitted greatly from being able to spend time with people not doing philosophy. Thanks are due to the university’s Taekwondo society and the members of CrossFit Leeds for helping to keep me sane during the process. It turns out the best solution is sometimes to just keep making a puddle of sweat until the problem doesn’t seem so big anymore! Also to Cassie Brummitt and Wally Hussain: you guys rock. This would have been a much more difficult project if not for the support of my girlfriend, Becky Bowd. Her faith throughout helped greatly. Massive thanks are due to my family for the innumerable ways in which they have assisted me. Most of all, I thank my parents, whose understanding and unwavering support has gone above and beyond what I could reasonably have expected. Finally, I am grateful for the financial support that I have received from the University of Leeds in the form of the Research Scholarship that enabled me to undertake this work. - v - Abstract Humeanism is often taken to be a prime example of metaphysics which has failed to be sufficient attention to contemporary science. I argue that these claims have been made too hastily: there are moves available to Humeans which bring the account closer to scientific practice while still preserving the spirit of the view. The thesis comprises two parts. In the first half, I deal with the Best System Account of laws, and consider how it ought to treat initial conditions. From there, I turn to the question of whether Humean laws can explain events. This has recently been a topic of renewed interest in the literature and I disentangle the various claims philosophers have made on behalf of Humeanism. From these, I identify three promising responses to the argument that Humean explanations are circular. In the second half of the thesis, I consider how the Humean approach to laws can be extended to cover symmetry principles when the latter are understood as laws of laws. In response to a problem concerning properties and language, I suggest that the account go language-relative. The result of this is a regularity-based approach that can incorporate both laws and their symmetries into a single unified framework. Finally, I draw upon some examples from biology to indicate how the account can deal with the special sciences. - vi - Table of Contents Acknowledgements ........................................................................................... iv Abstract .............................................................................................................. v Table of Contents ............................................................................................... vi Introduction ......................................................................................................vii Chapter 1 Humeanism ......................................................................................... 1 1.1 Humean Supervenience ............................................................................... 1 1.2 Laws as regularities .................................................................................... 12 1.3 Initial conditions ......................................................................................... 21 1.4 Targets of scientific inquiry ........................................................................ 36 Chapter 2 Humean explanations ....................................................................... 42 2.1 The circularity argument ............................................................................ 43 2.2 Metaphysical and scientific explanations .................................................. 49 2.3 The revised circularity argument ............................................................... 54 2.4 Irreducibility of the special sciences .......................................................... 60 2.5 Multiple realisability................................................................................... 62 2.6 Direction of grounding ............................................................................... 67 2.7 Is transitivity motivated? ........................................................................... 83 2.8 Explanatory pluralism................................................................................. 89 Chapter 3 Symmetries as metalaws ................................................................... 97 3.1 Introducing invariance ............................................................................... 97 3.2 Extending the BSA .................................................................................... 109 3.3 Miracles and exception clauses ............................................................... 132 3.4 The problem of language ......................................................................... 138 Chapter 4 The Humean account of metalaws ................................................... 147 4.1 Better Best Systems ................................................................................. 148 4.2 Symmetry principles and necessary connections .................................... 154 4.3 The special sciences ................................................................................. 162 Chapter 5 Conclusion ...................................................................................... 172 Bibliography ................................................................................................... 177 - vii - Introduction As philosophy is essentially a meta-activity, there can be philosophies of just about anything, and science is no exception … It [philosophy of science] has enjoyed a boom in the last 50 years or so, partly because it gives philosophers the unfamiliar sensation that what they are doing is of some relevance to something.1 This thesis works at the intersection of metaphysics and the philosophy of science. The area is something of a minefield: specialists from both of these areas of philosophy have been guilty of drawing battle lines around their respective subjects and declaring the middle ground to be a no man’s land. On the one hand, we find philosophers of science taking metaphysicians to task over a lack of scientific engagement. They accuse metaphysicians of indulging in debates that are sterile or empty, of ignoring parts of science clearly relevant to their projects and, on those occasions where metaphysicians remember to throw in a scientific reference, of using only radically simplified ‘domestications’ of science. In their influential critique, Ladyman and Ross draw a clear lesson from these failings, claiming that ‘contemporary analytic metaphysics, a professional activity engaged in by some extremely intelligent and morally serious people, fails to qualify as part of the enlightened pursuit of objective truth, and should be discontinued’.2 There are echoes of Hume here, and his insistence that such works of sophistry and illusion ought to be cast into the flames. In the face of such criticisms, some metaphysicians have dug their heels in and doubled down on what they have already been doing. This sentiment is nicely brought out – although not entirely endorsed – by Conee and Sider: The revised view is that metaphysics is about the most explanatorily basic necessities and possibilities. Metaphysics is about what could be and what must be. Except incidentally, metaphysics is not about explanatorily ultimate aspects of reality that are actual. Metaphysics is about some actual 1 Hankinson (1985) p. 40. 2 Ladyman and Ross (2007) vii. - viii - things, only because whatever is necessary has got