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. (shrink)

Canonical defenders of the principle of sufficient reason (PSR), such as Leibniz and Spinoza, are metaphysical foundationalists of one stripe or another. This is curious since the PSR—which says that everything has a ground, cause, or explanation—in effect, denies fundamental entities. In this paper, I explore the apparent inconsistency between metaphysical foundationalism and approaches to metaphysical system building that are driven by a commitment to the PSR. I do so by analyzing how Indian Buddhist philosophers arrive at (...) foundationalist and anti-foundationalist positions motivated by implicit commitments to different versions of the PSR. I begin by introducing the Buddhist principle of dependent origination (pratītyasamutpāda) as a proto-PSR that is restricted to causal explanation. Next, I show how Vasubandhu’s Sautrāntika Abhidharma metaphysics is shaped by a qualified commitment to both causal and metaphysical grounding versions of the PSR. I then reveal how Nāgārjuna’s Madhyamaka metaphysics is driven by an unrestricted and exceptionless commitment to causal and metaphysical grounding versions of the PSR. Finally, I consider how Nāgārjuna’s account may put him in a unique position to respond to a common contemporary objection to the PSR from necessitarianism. I conclude by addressing a competing interpretation on which Nāgārjuna is best understood as an anti-rationalist rather than an uber-rationalist, as I characterize him. (shrink)

The consensus is that in his 1755 Nova Dilucidatio, Kant endorsed broadly Leibnizian compatibilism, then switched to a strongly incompatibilist position in the early 1760s. I argue for an alternative, incompatibilist reading of the Nova Dilucidatio. On this reading, actions are partly grounded in indeterministic acts of volition, and partly in prior conative or cognitive motivations. Actions resulting from volitions are determined by volitions, but volitions themselves are not fully determined. This move, which was standard in medieval treatments of free (...) choice, explains why Kant is so critical of Crusius’s version of libertarian freedom: Kant understands Crusius as making actions entirely random. In defense of this reading, I offer a new analysis of the version of the principle of sufficient reason that appears in the Nova Dilucidatio. This principle can be read as merely guaranteeing grounds for the existence of things or substances, rather than efficient causes for states and events. As such, the principle need not exclude libertarian freedom. Along the way, I seek to illuminate obscure aspects of Kant’s 1755 views on moral psychology, action theory, and the threat of theological determinism. (shrink)

This essay deals with a Leibnizian version of the argument from the contingent existence of the world to the necessary existence of God, especially with the statements of the argument presented by Father Copleston in his famous B.B.C. debate with Bertrand Russell and, more recently, by Richard Taylor, in his Metaphysics. The essay is divided into two parts. In the first part, I am chiefly concerned with showing how the principle of sufficient reason, together with the claim that (...) something contingent exists, will allow us to conclude, without any appeal to the impossibility of an infinite series of contingent causes, that there exists a necessary being distinct from the world of contingent beings. In the second part of the essay, I try to show that, in a form strong enough to support the argument, the principle of sufficient reason has the implication—undesirable to many, but not all theists— that nothing could be logically contingent. (shrink)

The early modern period was the natural historical habitat of the Principle of Sufficient Reason, i.e., the demand that everything must have a cause, or reason. It is in this period that the principle was explicitly articulated and named, and throughout the period we find numerous formulations and variants of the PSR and its closely related ‘ex nihilo nihil fit’ principle, which the early moderns inherited from medieval philosophy. Contemporary discussions of these principles were not (...) restricted to philosophy. “Nothing will come of nothing; speak again” old King Lear tells his daughter Cordelia at the beginning of Shakespeare’s celebrated tragedy, and in early modern science, conservation principles were the order of the day. Within philosophy, Malebranche stipulates that there cannot be an effect without a cause, and Berkeley motivates his idealism by an appeal to ‘ex nihilo nihil fit.’ Were we to try to provide an exhaustive survey the various formulations of the PSR in this period – including the weaker ones – we would be writing an encyclopedia. In fact, one wonders whether any early modern thinker was willing to accept a wholesale rejection of the PSR, i.e., a view which states that no fact requires an explanation. Moreover, the view that many – perhaps most – facts require an explanation seems to be tacitly assumed even by us today, in both our theoretical and colloquial discourse. For these reasons, this chapter will focus on two early modern philosophers who advocated very strong (i.e., virtually exceptionless) versions of the PSR: Benedict de Spinoza and G.W. Leibniz. Following a brief overview of Descartes’s restricted endorsement of the PSR, I will turn to discuss the central features of the PSR in the writings of Spinoza (§2) and those of Leibniz (§3). In the cases of each of these philosophers, we will examine carefully: (i) their main statements of the PSR, (ii) the scope they assign to the principle (i.e., what requires an explanation and what counts as an explanation), (iii) the modal strength they assign to the principle, (iv) the main implications they draw from the principle, (v) exceptions to the principle, and, finally, (vi) the justification of the principle. In §4, we will study a principle, complementing the PSR, namely, the assertion that everything and every fact must have an effect (or as Leibniz would put it: “nothing is sterile”). (shrink)

The relation between leibniz's logical and his metaphysical views is the subject of much modern scholarship. Some commentators have argued that his metaphysics is based on his logic; others have taken the opposite position. However, Both sides pose the question in terms of 'priority'. On the contrary, I argue that it is likely that leibniz means the psr to play "both" a logical and a metaphysical role. The ambiguity of leibniz's psr indicates that he equates the metaphysical notion of causation (...) with the logical notion of deduction. The psr's ambiguity results less from any confusion on leibniz's part between the notions of cause and reason, Than from his desire to identify logic and metaphysics. That identity is achieved not by reducing one to the other, But by incorporating them on an equal basis into a single discipline. (shrink)

Contemporary arguments for scientific realism are typically based on some form of inference to the best explanation. Sometimes such arguments concern the methods of science: given the success of scientific methodology, realism offers the best explanation of this success. Sometimes such arguments concern the content of scientific theories: given observed regularities in nature, explanations must be given of those regularities; the best such explanations will be realist. One forceful explanationist argument about the content of science can be based on Hans (...) Reichenbach’s Principle of the Common Cause. Roughly, CC says that whenever an enduring correlation between two events is observed, there must be some preceding event which is the common cause of the two, and is the explanation for the correlation. Rigid adherence to this demand for a common cause, however, supposedly goes beyond the instrumentalist explanatory resources available to the antirealist, and hence CC is taken to be a sufficient condition for realism. Further, one might claim that any argument that realism has greater explanatory power than antirealism depends either explicitly or implicitly on CC, and hence CC is also a necessary condition for realism. (shrink)

The principle of causal exclusion is based on two distinct causal notions: causal sufficiency and causation simpliciter. The principle suggests that the former has the power to exclude the latter. But that is problematic since it would amount to claiming that sufficient causes alone can take the roles of causes simpliciter. Moreover, the principle also assumes that events can sometimes have both sufficient causes and causes simpliciter. This assumption is in conflict with the first part (...) of the principle that claims that sufficient causes must exclude causes simpliciter. (shrink)

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 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)

Behavioural variant frontotemporal dementia (bvFTD) is characterized by an absence of obvious cognitive impairment and presence of symptoms such as disinhibition, social inappropriateness, personality changes, hyper-sexuality, and hyper-orality. Affected individuals do not feel concerned enough about their actions to be deterred from violating social norms, and their antisocial behaviours are most likely caused by the neurodegenerative processes in the frontal and anterior temporal lobes. BvFTD patients present a challenge for the traditional notion of autonomy and the medical and criminal justice (...) systems. Antisocial behaviour is often the earliest recognized manifestation of bvFTD. Given that the symptoms are not specific and that atrophy of the frontal lobes is only observable with structural neuroimaging in the later stages of the disease, it is hard to ascertain their autonomy. Recently proposed re-conceptualizations of autonomy (Dworkin’s, Jaworska’s, and Dubljević’s) can, however, be sufficiently redefined to provide explicit rules and offer nuanced guidance in such cases. A combination of notions of autonomy gives the most nuanced guidance with three modifications: 1) including socio-moral judgement in the notion of “normal cognitive competence,” 2) excluding in-principle un-endorsable ideals from the notion of “capacity to value,” and 3) redefining ideal-typical degrees of compulsion (mild, severe, and total). (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)

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)

Mathias Frisch has argued that the requirement that electromagnetic dispersion processes are causal adds empirical content not found in electrodynamic theory. I urge that this attempt to reconstitute a local principle of causality in physics fails. An independent principle is not needed to recover the results of dispersion theory. The use of ‘causality conditions’ proves to be the mere adding of causal labels to an already presumed fact. If instead one seeks a broader, independently formulated grounding for the (...) conditions, that grounding either fails or dissolves into vagueness and ambiguity, as has traditionally been the fate of candidate principles of causality. Introduction Scattering in Classical Electrodynamics Sufficiency of the Physics Failure of the Principle of Causality Proposed 4.1 A sometimes principle 4.2 The conditions of applicability are obscure 4.3 Effects can come before their causes 4.4 Vagueness of the relata and of the notion of causal process Conclusion CiteULike Connotea Del.icio.us What's this? (shrink)

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)

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)

The concept of efficient causation originates with Aristotle, who states that the types of cause include ‘the primary source of the change or rest’. For Medieval Aristotelians, the scope of efficient causality includes creative acts. The Islamic philosopher Avicenna is an important contributor to this conceptual change. In his Metaphysics, Avicenna defines the efficient cause or agent as that which gives being to something distinct from itself. As previous studies of Avicenna's ‘metaphysical’ conception of the efficient cause (...) attest, it takes God as a model agent. This essay considers whether Avicenna's ‘metaphysical’ conception of the efficient cause applies to natural agents. It ultimately argues that Avicenna offers a unified view of the efficient cause, which includes both divine and natural agents. On this view, an efficient cause gives being to another and is simultaneous with its effect. While Avicenna's defence of this view is an important chapter in the history of the concept of the efficient cause, it is also of interest in its own right. By appeal to a version of the principle of sufficient reason, it challenges a widespread view that causes are temporally prior to their effects. (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.

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)

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.

This essay discusses two contributions of the principle of sufficient autonomy to educational justice. In Just Enough, Liam Shields criticizes instrumental accounts of autonomy. According to these accounts, autonomy is valuable insofar as it contributes to well-being. Shields argues that instrumental arguments fail to support mandatory autonomy education in all cases, while his non-instrumental principle of sufficient autonomy does support this. This essay develops a version of the instrumental argument and argues this version can do the (...) work of supporting mandatory autonomy education. Another contribution of the principle of sufficient autonomy is the requirement of talents discovery. According to Shields, the requirement of talents discovery renders Rawls’s principle of fair equality of opportunity more plausible, since one’s chances of accessing a given economic position depend on one’s opportunities to discover one’s innate talents. This essay argues that Rawlsian fair equality of opportunity does not have the same implications as the principle of sufficient autonomy as to which types of talents should be discovered and to what extent. (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)

In this paper I develop a novel response to the exclusion problem. I argue that the nature of the events in the causally complete physical domain raises the “problem of many causes”: there will typically be countless simultaneous low-level physical events in that domain that are causally sufficient for any given high-level physical event. This shows that even reductive physicalists must admit that the version of the exclusion principle used to pose the exclusion problem against non-reductive physicalism is (...) too strong. The burden is on proponents of the exclusion problem to provide a reason to think that any qualifications placed on the exclusion principle will solve the problem of many causes while ruling out causation by irreducible mental events. (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)

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)

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.

With the emergence of modern physics a conflict became apparent between the Principle of Sufficient Cause and the Principle of Physical Causal Closure. Though these principles are not logically incompatible, they could no longer be considered to be both true; one of them had to be false. The present paper makes use of this seldom noticed conflict to argue on the basis of considerations of comparative rationality for the truth of causal statements that have at least (...) some degree of philosophico-theological relevance and can be taken to indicate ( not prove) the existence of God. The paper’s comparatively modest aim is to establish belief in the existence of God as a rational metaphysical option, not as a rational obligation. In its final section, enriched causal considerations lead to an indication ( not proof) of God as that which guarantees the unified continuance of the physical world. (shrink)

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)

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)

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.

The Principle of Sufficient Reason must be justified dialectically: by showing the disastrous consequences of denying it. We formulate a version of the Principle that is restricted to basic natural facts, which entails the obtaining of at least one supernatural fact. Denying this principle results in extreme empirical skepticism. We consider six current theories of empirical knowledge, showing that on each account we cannot know that we have empirical knowledge unless we all have a priori knowledge (...) of the PSR. We consider objections based on Neo-Humeanism and the essentiality of origins, and we consider the possibility that we have empirical knowledge without knowing it. (shrink)

I distinguish three ways in which early modern rationalists seek to apply the principle of sufficient reason to empirical science, and critically assess some of their attempts to do so. I focus especially on how these thinkers assume substantive theories of explanation and intelligibility--which are indebted to the mechanist and experimentalist traditions--in many of their deployments of this rationalist principle. A recurring problem is that these philosophers deploy their standards of intelligibility inconsistently: some of their own favored (...) explanations do not always live up to their standards. I argue that the problem is especially acute for Leibniz and Euler, given their enthusiasm for final-causal explanations. (shrink)

The term “principle of sufficient reason” (PSR) was coined by Leibniz, and he is often regarded as its paradigmatic proponent. But as Leibniz himself often insisted, he was by no means the first philosopher to appeal to the idea that everything must have a reason. Histories of the principle attribute versions of it to various ancient authors. A few of these studies include—or at least do not exclude—medieval philosophers; one finds the PSR in Abelard, another finds it (...) in Aquinas. And while Leibniz retains pride of place in these histories, Spinoza is sometimes said to precede him “in appreciating the importance of the Principle and placing it at the center of his philosophical system.” In this paper, the author argues that the same should be said of the Islamic philosopher Avicenna. Writing 600 years before his early modern counterparts, Avicenna routinely and consistently appeals to the PSR in generating his metaphysical system. The paper aims first to establish that Avicenna deserves a position of prominence in histories of the PSR, and then to consider how he addresses certain challenges to the PSR, especially the threat posed by necessitarianism. (shrink)

The principle of sufficient reason threatens modal collapse. Some have suggested that by appealing to the indefinite extensibility of contingent truth, the threat is neutralized. This paper argues that this is not so. If the indefinite extensibility of contingent truth is developed in an analogous fashion to the most promising models of the indefinite extensibility of the concept set, plausible principles permit the derivation of modal collapse.