Leibniz and the Principle of Sufficient Reason by Owen Pikkert A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Philosophy University of Toronto © Copyright by Owen Pikkert 2018 Abstract Leibniz and the Principle of Sufficient Reason Owen Pikkert Doctor of Philosophy Department of Philosophy University of Toronto 2018 Leibniz’s principle of sufficient reason (PSR) is the claim that everything has an explanation. It rules out brute facts, inexplicable primitives, and purely random events. On the usual view, Leibniz grounds the PSR in purely descriptive truths. On my view, Leibniz grounds the PSR in this being the best of all possible worlds. God only creates the best, and a world in which the PSR is true is better than a world in which it is false. For the PSR ensures that the world has an explanatory structure, the investigation of which facilitates human happiness. This way of grounding the PSR faces at least two problems. The first problem is that it presupposes that the PSR is a contingent principle, even though most commentators take it to be necessary. But I argue that Leibniz is indeed committed to the contingency of the PSR. I demonstrate this by showing how, for Leibniz, PSR-violating entities such as vacua, atoms, and indiscernible bodies are possible but not actual. I also argue that the contingency of the ii PSR does not conflict with Leibniz’s other modal commitments. In particular, it does not conflict with the modal status of his principle of the identity of indiscernibles, nor with the modal status of his theory of truth. The second problem is that this way of grounding the PSR seems to be circular. For the PSR cannot be partially grounded in God’s choice of the best if God’s choice of the best is itself grounded in the PSR. I argue that Leibniz avoids this problem by grounding God’s choice of the best not in the PSR, but in God’s aim to maintain his own happiness. A suboptimal world would compromise God’s happiness, so he only creates the best. This constitutes a novel interpretation of Leibniz’s view that God has created the best of all possible worlds. iii Acknowledgments I am most grateful to Marleen Rozemond, an excellent and dedicated supervisor. I am also grateful to the other members of my supervisory committee: Donald Ainslie, Karolina Hübner, William Seager, and, as external readers, Deborah Black and Martin Lin. Further thanks are due to the following persons for commenting on individual chapters: Christian Barth, Sebastian Bender, Marc Bobro, Michael Della Rocca, Robert Mason, Jeff McDonough, and Matthew Wurst. Michael Della Rocca deserves special mention for generously advising me while I spent a term at Yale during the early stages of this dissertation. Finally, I gratefully acknowledge funding from the Social Sciences and Humanities Research Council of Canada, and from the Balzan Styles of Reasoning Project at the University of Toronto. iv Table of contents A note about citations vii 1. Introduction 1 1. Overview of the dissertation 3 2. What is Leibniz’s PSR? 5 2. The grounds of the PSR 19 1. Clarifying the question 19 2. The nature of necessary and sufficient conditions 21 3. The nature of truth 26 4. Harmony 29 5. God’s wisdom 32 3. The modal status of the PSR 40 1. Absolute possibility 41 2. The absolute possibility of indiscernibles 45 v 3. Indiscernibles and the PSR 50 4. Problems for indiscernibles as violations of the PSR 53 4. God’s choice of the best 68 1. The argument from the PSR 70 2. The argument from the will 73 3. Leibniz’s official argument 77 4. God’s happiness 80 5. The cosmological argument 93 1. Leibniz’s formulation of the cosmological argument 94 2. The mereological interpretation 99 3. The modal interpretation 104 4. The contrastive interpretation 111 Conclusion 119 References 122 vi A note about citations Leibniz’s writings appear in many different volumes compiled by many different editors. Matters are further complicated by the fact that the official Akademie edition of Leibniz’s works is far from complete. I have adopted the following conventions to keep things as straightforward as possible. Each time I mention or discuss one of Leibniz’s writings, I include both the title and the date either in the body of the text or in the corresponding footnote. Letters are dated to the nearest known day, whereas all other writings are dated to the nearest known year. Note that many titles are the creations of later editors. I have preserved these titles, however, for the purpose of comparing references and to stimulate the memory of the reader already used to such titles. In all cases I provide a citation both to the writing as it appears in its original language and as it appears in translation. The one exception is when a writing is cited from the Yale Leibniz Series (CP, DSR, LDB, LDV, LoC). This is because the Yale editions provide both the original language and the translation on opposing pages. In such cases I tend only to cite the Yale edition. vii 1. Introduction Suppose someone comes across a house in a secluded area. There is much about this house that cries out for explanation: its strange location, the identity of its owner, and its current occupancy. But there is also much about this house that is perfectly normal: it has a front door, it is made out of bricks, and it has three bedrooms. Presumably, all of these facts have some explanation. And presumably, the explanation for these facts will appeal to other facts that themselves have an explanation. It will not do to say of any fact that it is absolutely brute, without any explanation whatsoever. Anyone who feels the force of these intuitions feels the force of the principle of sufficient reason (PSR), the claim that everything has an explanation that is sufficient to explain why it is so and not otherwise. Indeed, for many the PSR seems obviously true – so obvious, in fact, that it is remarkable to them that anyone would question the PSR at all. Yet it is a controversial principle. Perhaps the most influential early challenge was advanced by Hume, who, by allowing for the possibility of something to exist without a cause, thereby denied that the PSR is necessarily true.1 For if it is possible to have something without any cause, then there will be no explanation for why it occurs. More recently, a number of philosophers have denied that the PSR is true at all. They point to the fact that the PSR seems 1 Treatise 1.3.3.3. Della Rocca (2014: 7) reads this as “an argument against the PSR or, at least, against the necessity of the PSR.” 1 to imply some form of necessitarianism, and that it conflicts with certain interpretations of quantum mechanics.2 Possibly due to the influence of such objections, some philosophers now treat the PSR as a purely pragmatic principle.3 They advocate that we should continue to assume the PSR in our reasoning, though not because it must reflect the fundamental nature of reality. In fact, our investigations might uncover certain brute features of the world, and we should accept them as such. In their view, the PSR is a purely methodological principle: it can be violated in certain cases, and possibly abandoned altogether. Other philosophers, however, see this retreat as premature. Some of them have questioned whether the objections from necessitarianism and from quantum mechanics are sound.4 And others have even attempted to defend versions of the PSR itself.5 In recent years exciting work has been done on both fronts. The time is therefore ripe to consider how the principle’s most famous historical proponent, Gottfried Wilhelm Leibniz (1646-1716), understood and employed his great principle. In this dissertation, that is what I shall attempt to do. 2 Necessitarianism: van Inwagen (1983: 202-204; 2015: 164-167), Bennett (1984: 115). Quantum mechanics: Grünbaum (2005: 151-152), van Inwagen (2015: 164). 3 Schlesinger (1995), Wiggins (1996). 4 Replies to the objection from necessitarianism: Lin (2012), Schnieder and Steinberg (2016), Levey (2016). Reply to the objection from quantum mechanics: Pruss (2006: 160-170). 5 Pruss (2006), Della Rocca (2010), Dasgupta (2016). 2 1. Overview of the dissertation The dissertation is structured as follows. In the remainder of this introductory chapter I examine more closely what exactly Leibniz took the PSR to be. This is necessary to address more theoretical concerns regarding the PSR, concerns that are taken up in subsequent chapters. In chapter 2 I examine the grounds of the PSR itself. In virtue of what does Leibniz think that the PSR is true? I consider and reject three answers: that the PSR is grounded in the nature of necessary and sufficient conditions; that it is grounded in the nature of truth; and that it is grounded in the world’s harmony. Instead, I suggest that the PSR is grounded in God’s wisdom. A wise God always acts for the best, and so will create a world in which the PSR is true. This is because a PSR world is one with an explanatory structure, the investigation of which increases the happiness of its creatures. Thus the PSR is really grounded in another principle, namely the principle of the best, as well as the way in which the truth of the PSR contributes to a world’s goodness. In chapter 3 I consider whether the PSR is necessary or contingent.