I offer an analysis of the Principle of Sufficient Reason and its relevancy for the scientific endeavour. I submit that the world is not, and cannot be, rational—only some brained beings are. The Principle of Sufficient Reason is not a necessary truth nor a physical law. It is just a guiding metanomological hypothesis justified a posteriori by its success in helping us to unveil the mechanisms that operate in Nature.

The Principle of Sufficient Reason is very seldom, if ever, referred to in the works of whom we might think of as the eminent Asian metaphysicians. In spite of this, the big picture metaphysical views available in the thought of philosophers such as Nāgārjuna, Fazang and Nishida appear to share certain structural features with views more familiar to us from our own tradition; views that explicitly accept or reject the Principle of Sufficient Reason. Nāgārjuna looks to (...) develop a kind of metaphysical infinitism, Fazang an extreme form of coherentism, and Nishida a species of foundationalism. These three positions - infinitism, coherentism and foundationalism - are typically thought to exhaust the spread of possibilities by those working within the Western tradition. -/- In spite of their similarities to positions advanced within our own tradition, the cosmologies of many of the giants of Asian philosophy are characterised by their rather striking conclusions. Amongst such conclusions for Nāgārjuna is that everything is empty; for Fazang that everything is identical to everything else; and for Nishida that everything depends on absolute nothingness. If the Principle of Sufficient Reason is playing a role in the derivation of such striking conclusions, then it looks that there are more options regarding the metaphysical structure of the world available to us than our own tradition typically courts. If, on the other hand, these striking cosmological conclusions are arrived at without any consideration of sufficient reason, then there may well be ways of reasoning about the overarching structure of reality that are powerful but unfamiliar to Western thinking. In this contribution, I explore what, if any, role the PSR might be playing in the thought of Nāgārjuna , Fazang and Nishida, and what we might be able to learn from it. (shrink)

The Principle of Sufficient Reason says that all contingent facts must have explanation. In this 2006 volume, which was the first on the topic in the English language in nearly half a century, Alexander Pruss examines the substantive philosophical issues raised by the Principle Reason. Discussing various forms of the PSR and selected historical episodes, from Parmenides, Leibnez, and Hume, Pruss defends the claim that every true contingent proposition must have an explanation against major objections, including Hume's (...) imaginability argument and Peter van Inwagen's argument that the PSR entails modal fatalism. Pruss also provides a number of positive arguments for the PSR, based on considerations as different as the metaphysics of existence, counterfactuals and modality, negative explanations, and the everyday applicability of the PSR. Moreover, Pruss shows how the PSR would advance the discussion in a number of disparate fields, including meta-ethics and the philosophy of mathematics. (shrink)

This chapter provides an overview and critical discussion of cosmological arguments for theism, with special focus on the Kalam argument and arguments from contingency.

The Clarke/Rowe version of the Cosmological Argument is sound only if the Principle of Sufficient Reason is true, but many philosophers, including Rowe, think that there is not adequate evidence for the principle of sufficient reason. I argue that there may be indirect evidence for PSR on the grounds that if we do not accept it, we lose our best justification for an important principle of metaethics, namely, the Principle of Universalizability. To show this, I argue (...) that all the other justifications of the Principle of Universalizability on offer, including Richard Hare's, are inadequate. (shrink)

In the standard analysis of economic institutions--which include social conventions, the working rules of an economy, and entitlement regimes --economists invoke the same theories they use when analyzing individual behavior. In this profoundly innovative book, Daniel Bromley challenges these theories, arguing instead for "volitional pragmatism" as a plausible way of thinking about the evolution of economic institutions. Economies are always in the process of becoming. Here is a theory of how they become. Bromley argues that standard economic accounts see institutions (...) as mere constraints on otherwise autonomous individual action. Some approaches to institutional economics--particularly the "new" institutional economics--suggest that economic institutions emerge spontaneously from the voluntary interaction of economic agents as they go about pursuing their best advantage. He suggests that this approach misses the central fact that economic institutions are the explicit and intended result of authoritative agents--legislators, judges, administrative officers, heads of states, village leaders--who volitionally decide upon working rules and entitlement regimes whose very purpose is to induce behaviors that constitute the sufficient reasons for the institutional arrangements they create. Bromley's approach avoids the prescriptive consequentialism of contemporary economics and asks, instead, that we see these emergent and evolving institutions as the reasons for the individual and aggregate behavior their very adoption anticipates. These hoped-for outcomes comprise sufficient reasons for new laws, judicial decrees, and administrative rulings, which then become instrumental to the realization of desired individual behaviors and thus aggregate outcomes. (shrink)

Most of the historically salient versions of the Cosmological Argument rest on two assumptions. The first assumption is that some contingeney (i.e., contingent fact) is such that a necessity is required to explain it. Against that assumption we will argue that necessities alone cannot explain any contingency and, furthermore, that it is impossible to explain the totality of contingencies at all.The second assumption is the Principle of Sufficient Reason. Against the Principle of Sufficient Reason we will (...) argue that it is unreasonable to require, as the Principle of Sufficient Reason does, that any given whole of contingent facts has an explanation. Instead, it depends on the results of empirical investigation whether or not one should ask for an explanation of the given whole.We argue that if a cosmological argument invokes either of the two assumptions, then it fails to prove that a necessity is needed to explain the universe of contingent facts. (shrink)

According to the Principle of Sufficient Reason (henceforth ‘PSR’), everything has an explanation or sufficient reason. This paper addresses three questions. First, how continuous is the contemporary notion of grounding with the notion of sufficient reason endorsed by Spinoza, Leibniz, and other rationalists? In particular, does a PSR formulated in terms of ground retain the intuitive pull and power of the PSR endorsed by the rationalists? Second, to what extent can the PSR avoid the (...) formidable traditional objections levelled against it if it is formulated in terms of ground? And finally, how might historical discussion of the PSR shed light on the contemporary notion of grounding? (shrink)

The Principle of Sufficient Reason is a powerful and controversial philosophical principle stipulating that everything must have a reason or cause. This simple demand for thoroughgoing intelligibility yields some of the boldest and most challenging theses in the history of metaphysics and epistemology. In this entry we begin with explaining the Principle, and then turn to the history of the debates around it. A section on recent discussions of the Principle will be added in the near future.

Peter van Inwagen presented a powerful argument against the Principle of Sufficient Reason, which I henceforth abbreviate as ‘PSR’. For decades, the consensus was that this argument successfully refuted PSR. However, now a growing consensus holds that van Inwagen’s argument is fatally flawed, at least when ‘sufficient reason’ is understood in terms of ground, for on this understanding, an ineliminable premiss of van Inwagen’s argument is demonstrably false and cannot be repaired. I will argue that this (...) growing consensus is mistaken and that a powerful argument relevantly similar to van Inwagen’s should still concern us, even when we understand ‘sufficient reason’ in terms of ground. (shrink)

Ralph Walker; VI*—Sufficient Reason, Proceedings of the Aristotelian Society, Volume 97, Issue 1, 1 June 1997, Pages 109–124, https://doi.org/10.1111/1467-9264.

Ralph Walker; VI*—Sufficient Reason, Proceedings of the Aristotelian Society, Volume 97, Issue 1, 1 June 1997, Pages 109–124, https://doi.org/10.1111/1467-9264.

In On What Matters Derek Parfit advocates the Kantian Contractualist Formula as one of three supreme moral principles. In important cases, this formula entails that it is wrong for an agent to act in a way that would be partially best. In contrast, Parfit’s wide value-based objective view of reasons entails that the agent often have sufficient reasons to perform such acts. It seems then that agents might have sufficient reasons to act wrongly. In this paper I will (...) argue that such reasons are a symptom of a fundamental inconsistency between the Kantian Contractualist Formula and Parfit’s view of reasons. The formula requires that we consider what everyone could rationally will, while a wide value-based objective view requires that we consider only what the agent has sufficient reasons for doing. The same inconsistency is particularly obvious in Parfit’s version of the Consent Principle, which share important features with the Kantian Contractualist Formula. Parfit accepts that moral principles might entail that we sometimes have sufficient reasons to act wrongly. However, to accept that supreme moral principles have such implications is objectionable if you, like Parfit, also hold that principles with such implications should be rejected or revised. I suggest that we could abandon the requirement that we have to consider the reasons of everyone. This would make the Kantian Contractualist Formula consistent with Parfit’s view of reasons, at least in this respect. I also argue that we can keep most implications of the Kantian Contractualist Formula that Parfit finds attractive. (shrink)

Leibniz was a philosopher of principles: the principles of Contradiction, of Sufficient Reason, of Identity of Indiscernibles, of Plenitude, of the Best, and of Continuity are among the most famous Leibnizian principles. In this article I shall focus on the first three principles; I shall discuss various formulations of the principles (sect. 1), what it means for these theses to have the status of principles or axioms in Leibniz’s philosophy (sect. 2), the fundamental character of the Principles of (...) Contradiction and Sufficient Reason (sect. 3), some attempts to demonstrate the Principles of Contradiction and Sufficient Reason (sect. 4), and one attempt to demonstrate the Principle of Identity of Indiscernibles (sect. 5). The main results of the chapter are summarized in a short conclusion (sect. 6). (shrink)

My aim is to show that supervenience claims follow from instances of a principle I call the principle of defeasibly sufficient reason. This principle construes the completeness of physics quite differently from strong or reductive physicalism and encodes both scientific and common sense patterns of explanation and justification. Rather than thoroughly defending the principle in the short space of this paper, I will sketch how one might defend it and a resulting fainthearted physicalism.

Alexander Pruss’s Principle of Sufficient Reason states that every contingent true proposition has an explanation. Pruss thinks that he can plausibly maintain both his PSR and his account of libertarian free will. This is because his libertarianism has it that contingent true propositions reporting free choices are self-explanatory. But I don’t think Pruss can plausibly maintain both his PSR and libertarianism without a rift occurring in one or the other. Similar to the old luck/randomness objection, I contend that (...) Pruss’s libertarianism is susceptible to what I call “the inexplicability objection”, which attempts to show that agents’ free choices involve contingent brute facts. Pruss may be able to partially explain a proposition such that Jones freely chose A for reason R, but he cannot adequately explain a contrastive proposition such as that Jones freely chose A for R rather than B for R*. The result is that either PSR is too explanatorily permissive for libertarianism, or libertarianism is too explanatorily impermissive to satisfy PSR. After considering what I take to be Pruss’s best response to the inexplicability objection, I conclude that his attempt to reconcile PSR and libertarianism is unsuccessful. (shrink)

Toward the end of his classic treatise An Essay on Free Will, Peter van Inwagen offers a modal argument against the Principle of Sufficient Reason which he argues shows that the principle “collapses all modal distinctions.” In this paper, a critical flaw in this argument is shown to lie in van Inwagen’s beginning assumption that there is such a thing as the conjunction of all contingently true propositions. This is shown to follow from Cantor’s theorem and a property (...) of conjunction with respect to contingent propositions. Given the failure of this assumption, van Inwagen’s argument against the Principle of Sufficient Reason cannot succeed, at least not without the addition of some remarkable and previously unacknowledged qualifications. (shrink)

It can be shown by means of a paradox that, given the Principle of Sufficient Reason, there is no conjunction of all contingent truths. The question is, or ought to be, how to interpret that result: _Quid sibi velit?_ A celebrated argument against PSR due to Peter van Inwagen and Jonathan Bennett in effect interprets the result to mean that PSR entails that there are no contingent truths. But reflection on parallels in philosophy of mathematics shows it can (...) equally be interpreted either as a proof that there are "too many" contingent truths to combine in a single conjunction or as a proof that the concept _contingent truth_ is indefinitely extensible and there is no such thing as "all contingent truths." Either interpretation would reconcile PSR with contingent truth, but the natural rationales of those interpretations are at odds. This essay argues that the second interpretation is a more satisfactory explanation of why, if PSR is true, there should be no conjunction of all contingent truths. This sheds new light on the nature of the explanatory demand embedded in PSR and uncovers a number of surprising implications for the commitments of rationalism. (shrink)

The Southern Journal of Philosophy, EarlyView.

I show how the Cosmological Argument (CA) is undermined by one of its own premises: the Principle of Sufficient Reason (PSR). First, I explain the type of CA that I am thinking about. Second, I explain a traditional modal objection against the PSR, which is ultimately based upon our intuitions in favor of contingency. Third, I show how this modal objection begs the question against the necessitarian, and then I reformulate the CA in more neutral terms. Fourth, using (...) this more neutral version of the CA, I argue that the main problem with the PSR goes way beyond its apparent necessitarian consequences. As an argument used by Bradley shows, embracing the rationalist path that underlies the PSR seems to commit us to a form of Radical Monism. I conclude by showing how this result ultimately undermines the CA. (shrink)

Leibniz' Prinzip des zureichenden Grundes soll hier aufgrund von Russells Begriff des ‛logischen Eigennamens’ untersucht werden. Aus dieser Sicht kann vor der Schöpfung Gottes Begriff von Individuen keine individuelle Diesheit haben, sondern nur eine vollständige Beschreibung der noch nicht existierenden Individuen. Daraus ergibt sich, daß ein und dasselbe Individuum nicht durch mehr als eine Weltbeschreibung identifiziert werden kann, und darin darf man folglich Leibniz' tatsächlichen Beweis für die These des ‛Superessentialismus’ sehen, demzufolge alle Individuen ihre gesamten Eigenschaften mit Ausnahme der (...) Existenz wesenhaft besitzen. Im weiteren wird der Begriff einer Art möglicher Welten, die wir ‛parasitisch’ nennen wollen, erforscht. Dieser Begriff wird Leibniz' theoretischen Voraussetzungen gerecht, ohne zu seinen wenig überzeugenden Schlüssen zu führen. (shrink)

This essay examines arguments offered in support of the Principle of Sufficient Reason (PSR) by Leibniz and his followers as well as Hume's critique of the PSR. It is shown that Leibniz has a defensible argument for the PSR, whereas the arguments of his self-proclaimed followers are weak. Thus, Hume's challenge is met by Leibniz, by Wolff and Baumgarten not so much.

This little-known work by the famous German pessimist and critic of Hegel was originally written as a doctoral dissertation when Schopenhauer was just twenty-six, but it was later revised when the philosopher was sixty. So important did he consider this work, originally titled "On the Fourfold Root of the Principle of Sufficient Reason," that he often underscored the fact that no one could hope to understand his magnum opus, The World as Will and Representation, without having first read (...) this work. Schopenhauer takes up where Kant left off in response to Hume, and his insights into the nature of perception and understanding remain amazingly relevant and still unsurpassed. Schopenhauer's analyses of causation and related concepts rival and probably surpass in their depth and brilliance the more celebrated discussions of David Hume. Where Hume grossly oversimplified these problems and left them riddled with paradoxes, Schopenhauer disentangled them and shed light on what had seemed hopelessly dark. (shrink)

Kant's attack on metaphysics consists in large part in his attack on a principle that he names the Supreme Principle of Pure Reason. This principle, it is not often noticed, is the Principle of Sufficient Reason [PSR]. In interpreting this principle as such, I argue that Kant's attack on the PSR depends on Kant's claim that existence is not a first-order predicate. If existence isn't what Kant calls a real predicate, the PSR is false. While this constitutes (...) a powerful Kantian argument against dogmatic rationalism, it also poses a problem for Kant. For, as I argue, if the PSR is true, Kant's argument that existence isn't a first-order predicate is false. In this sense, Kant's attack on the PSR is begging the question vis-á-vis radical metaphysicians. Concluding the paper I suggest relying on Kant's 'is'/'ought' distinction in avoiding this circularity, thereby reinforcing the Kantian critique. (shrink)

I examine Leibniz’s version of the Principle of Sufficient Reason with respect to free will, paying particular attention to Peter van Inwagen’s argument that this principle leads to determinism. Ultimately I conclude that Leibniz’s formulation is incompatible with free will. I then discuss a reformulation of the Principle of Sufficient Reason endorsed by Alexander Pruss that, I argue, manages to both retain the strength of Leibniz’s formulation and remain consistent with free will.

Machine generated contents note: General editor's preface; Editorial notes and references; Introduction; Notes on text and translation; Chronology; Bibliography; Part I. On the Fourfold Root of the Principle of Sufficient Reason: 1. Introduction; 2. Survey of what is most important in previous teachings about the principle of sufficient reason; 3. Inadequacy of previous accounts and sketch of a new one; 4. On the first class of objects for the subject and the form of the principle of (...) sufficient reason governing in it; 5. On the second class of objects for the subject and the form of the principle of sufficient reason governing in it; 6. On the third class of objects for the subject and the form of the principle of sufficient reason governing in it; 7. On the fourth class of objects for the subject and the form of the principle of sufficient reason governing in it; 8. General remarks and results; Variants in different editions; Collation of the two editions; Part II. On Vision and Colours: 9. On vision; 10. On colours; Variants in different editions; Part III. On Will in Nature: 11. Introduction; 12. Physiology and pathology; 13. Comparative anatomy; 14. Plant physiology; 15. Physical astronomy; 16. Linguistics; 17. Animal magnetism and magic; 18. Sinology; Reference to ethics; Conclusion; Variants in different editions; Glossary of names; Index. (shrink)

This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be (...) preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant. (shrink)

How radical is the idea that reasons are factive? Some philosophers consider it a dramatic departure from orthodoxy, with surprising implications about the bearing of the external world on what credences it’s reasonable to have, what beliefs are epistemically appropriate, and what actions are rational. I deny these implications. In the cases where external matters imply differences in factive states, there will inevitably be important weaker factive states in common. For example, someone who knows it is raining has many factive (...) states in common with someone who has a Gettiered belief that it is raining, or one who falsely but justifiably believes that it is raining. The factive reasons denied to subjects in Gettier cases or skeptical scenarios are in an important sense redundant; appropriate belief or action supervenes on internal states, even if reasons must be factive (and even if appropriate belief and action supervenes on reasons). The degree to which the strategy is applicable depends substantively on epistemic assumptions about basic or foundational knowledge. I argue that even given a significantly externalist approach to the latter internalist intuitions about rational credence, belief, and action can be vindicated. (shrink)

The paper is about the physical theories which result when one identifies points in phase space related by symmetries; with applications to problems concerning gauge freedom and the structure of spacetime in classical mechanics.

In The Metaphysics of Creation and The Metaphysics of Theism, Norman Kretzmann defends an argument for God's existence which he claims to find in Aquinas. I assess this argument's key premise, a principle of sufficient reason, that: ‘PSR2: Every existing thing has a reason for its existence either in the necessity of its own nature or in the causal efficacy of some other beings’. PSR2 requires God's nature to explain His existence. Kretzmann does not tell us how (...) this explanation is supposed to go. I examine such ways as I can envision that God's own nature might explain His existence. None pan out. I argue contra Kretzmann that if God is simple, as Aquinas understood this, His nature does not explain His existence, and while His existence is in itself per se notum (‘self-evident’) this does not entail that it has an explanation. If this is correct, we ought not to read Aquinas as committed to PSR2. Further, if I'm right that it's impossible for ‘the necessity of a thing's nature’ to explain its existence, PSR2 is true only if every existing thing has a reason for its existence in the causal efficacy of some other beings. So, if I'm right, theists ought to steer clear of PSR2, at least read in terms of genuine explanation. I finally offer a weaker reading of ‘a reason for its existence’ which does not generate the problems of the stronger reading Kretzmann seems to have in mind. This too, though, turns out to have its problems. (shrink)

Leibniz often refers to the Principle of Sufficient Reason (PSR) as something like a first principle. In some texts, however, he attempts to give positive arguments in its favor. I examine two such arguments, and find them wanting. The first argument has two defects. First, it is question-begging; and second, when the question-begging step is excised, the principle one can in fact derive is highly counter-intuitive. The second argument is valid, but has the defect of only reaching a (...) nearly trivial conclusion. (shrink)

Whether or not the principle of sufficient reason is a fundamental rule of formal logic is a question that merits serious discussion. In debates from as early as the 1960s, when discussing the subject and functions of formal logic, some comrades pointed out that formal logic cannot study just the forms of thought alone. One of their basic arguments was that "the principle of sufficient reason demands that the content of a premise must be true." In (...) discussions concerning the truth and validity of formal logic, some comrades likewise suggested that the validity of thought forms and the truth of their content were identical, their reason being that "one of the demands of the principle of sufficient reason is that a reason must be true." These discussions have already touched on the question of the nature of the principle of sufficient reason. Thus, this discussion now under way is a continuation and deepening of the past discussions on logic. Not only does it involve the content of the principle of sufficient reason and its role and function in formal logic, it also involves the object of study and the direction of the future development of this science, formal logic. The discussion of this problem is undoubtedly highly significant. (shrink)

Leibniz, and many following him, saw the Principle of Sufficient Reason (PSR) as pivotal to a scientific (demonstrated) metaphysics. Against this backdrop, Kant is expected to pay close attention to PSR in his reflections on the possibility of metaphysics, which is his chief concern in the Critique of Pure Reason. It is far from clear, however, what has become of PSR in the Critique. On one reading, Kant has simply turned it into the causal principle of the (...) Second Analogy. On a different reading, PSR is but the supreme principle of reason, which roughly states that, if the conditioned is given, so is the unconditioned. On my reading, PSR appears in the guises of both the causal principle and the supreme principle. This twofold specification, I argue, is key to understanding (i) Kant’s allegations that past metaphysicians failed to prove PSR, (ii) his own Critical account of the possibility of metaphysics in both of its parts (ontology and metaphysics proper), and (iii) his nuanced answer to the contentious question about the relation between physical inquiry and metaphysical reasoning about nature (both being quests for reasons). (shrink)

The aim of this paper is to defend the ontological Principle of Sufficient Reason (PSR-O). I analyse various versions of this principle and various ways of justifying it. Then I attempt to challenge some counterexamples allegedly refuting a universal application of the PSR-O. There are standard and non-standard versions of the PSR-O. The PSR-Ostand can only be valid if there are no chains of contingent reasons and outcomes with first modules, i.e. all chains are actually infinite. However, there (...) are serious arguments against this possibility. The necessary condition of the PSR-Onon-stand is the existence of a necessary substance: that substance would be a direct reason of certain contingent states of affairs obtaining in its domain, and those states of affairs would then be indirect reasons for all other contingent states of affairs and things. There are two advantages of the PSR-Onon-stand: a nomological unity of the world and explanatory simplicity. (shrink)

Ismay Barwell, Kathleen Lennon; II*—The Principle of Sufficient Reason, Proceedings of the Aristotelian Society, Volume 83, Issue 1, 1 June 1983, Pages 19–34, h.

Ismay Barwell, Kathleen Lennon; II*—The Principle of Sufficient Reason, Proceedings of the Aristotelian Society, Volume 83, Issue 1, 1 June 1983, Pages 19–34, h.

To sum up the main results of this study: I have disentangled two distinct patterns of argument that Taylor runs together in his attempt to show that there is a reason or explanation for the world as a whole. The first is based on the causal dependency of things in the world, the second is based on their logical contingency. It seems to make the most sense of Taylor's discussion if we interpret him not as invoking the principle of (...) sufficient reason at the crucial juncture, but as using these arguments to give backing to that principle by showing that it applies to the world in its totality. However, these arguments do not succeed in doing that. The first fails because it depends on a remote analogy between the world as a whole and the physical objects in the world. Concerning the second, an analysis of the logic of why-questions about the existence of things has revealed that the logical contingency of something is not a ground for thinking it has an explanation. The only promising interpretation of the principle of sufficient reason that we have found is as a causal principle pertaining to things in nature. (shrink)

The Clarke/Rowe version of the Cosmological Argument is sound only if the Principle of Sufficient Reason (PSR) is true, but many philosophers, including Rowe, think that there is not adequate evidence for the principle of sufficient reason. I argue that there may be indirect evidence for PSR on the grounds that if we do not accept it, we lose our best justification for an important principle of metaethics, namely, the Principle of Universalizability. To show this, I (...) argue that all the other justifications of the Principle of Universalizability on offer, including Richard Hare's, are inadequate. (shrink)

I argue that Émilie Du Châtelet breaks with Christian Wolff regarding the scope and epistemological content of the principle of sufficient reason, despite his influence on her basic ontology and their agreement that the principle of sufficient reason has foundational importance. These differences have decisive consequences for the ways in which Du Châtelet and Wolff conceive of science.

Of late I have read in earnest the article by Comrade Lin Mingjun et al. entitled "The Law of Sufficient Reason Is Not a Basic Law of Formal Logic" and Comrade Li Xiankun's article "The Position and Function of the Law of Sufficient Reason in Formal Logic" . In this article I'd like to set forth my opinions as they differ from theirs.

According to Principles of Sufficient Reason, every truth (in some relevant group) has an explanation. One of the most popular defenses of Principles of Sufficient Reason has been the presupposition of reason defense, which takes endorsement of the defended PSR to play a crucial role in our theory selection. According to recent presentations of this defense, our method of theory selection often depends on the assumption that, if a given proposition is true, then it has (...) an explanation, and this will only be justified if we think this holds for all propositions in the relevant group. I argue that this argument fails even when restricted to contingent propositions, and even if we grant that there is no non-arbitrary way to divide true propositions that have explanations from those that lack them. Further, we can give an alternate explanation of what justifies our selecting theories on the basis of explanatory features: the crucial role is not played by an endorsement of a PSR, but rather by our belief that, prima facie, we should prefer theories that exemplify explanatory power to greater degrees than their rivals. This guides our theory selection in a manner similar to ontological parsimony and theoretical simplicity. Unlike a PSR, our belief about explanatory power gives us a prima facie guiding principle, which provides justification in the cases where we think we have it, and not in the cases where we think we don't. (shrink)

Journal Name: Apeiron Issue: Ahead of print.