Graham Priest presents an exploration of the development of Buddhist metaphysics, which is viewed through the lens of the catuskoti. In its earliest and simplest form this is a logical/metaphysical principle which says that every claim is true, false, both, or neither; but Priest shows how the principle itself evolves as the metaphysics develops.

Dialetheism is the view that some contradictions are true. This is a view which runs against orthodoxy in logic and metaphysics since Aristotle, and has implications for many of the core notions of philosophy. Doubt Truth to Be a Liar explores these implications for truth, rationality, negation, and the nature of logic, and develops further the defense of dialetheism first mounted in Priest's In Contradiction, a second edition of which is also available.

Graham Priest presents an expanded edition of his exploration of the nature and limits of thought. Embracing contradiction and challenging traditional logic, he engages with issues across philosophical borders, from the historical to the modern, Eastern to Western, continental to analytic.

Graham Priest presents a ground-breaking account of the semantics of intentional language--verbs such as "believes," "fears," "seeks," or "imagines." Towards Non-Being proceeds in terms of objects that may be either existent or non-existent, at worlds that may be either possible or impossible. The book will be of central interest to anyone who is concerned with intentionality in the philosophy of mind or philosophy of language, the metaphysics of existence and identity, the philosophy of fiction, the philosophy of mathematics, or cognitive (...) representation in AI. (shrink)

This is a philosophical investigation of the nature of the limits of thought. Drawing on recent developments in the field of logic, Graham Priest shows that the description of such limits leads to contradiction, and argues that these contradictions are in fact veridical. Beginning with an analysis of the way in which these limits arise in pre-Kantian philosophy, Priest goes on to illustrate how the nature of these limits was theorised by Kant and Hegel. He offers new interpretations of Berkeley's (...) master argument for idealism and Kant on the antimonies. He explores the paradoxes of self reference, and provides a unified account of the structure of such paradoxes. The book concludes by tracing the theme of the limits of thought in modern philosophy of language, including discussions of the ideas of Wittgenstein and Derrida. (shrink)

Published in the American Journal of Bioethics.

Boring Formless Nonsense intervenes in an aesthetics of failure that has largely been delimited by the visual arts and its avant-garde legacies. It focuses on contemporary experimental composition in which failure rubs elbows with the categories of chance, noise, and obscurity. In these works we hear failure anew. We hear boredom, formlessness, and nonsense in a way that gives new purchase to aesthetic, philosophical, and ethical questions that falter in their negative capability. Reshaping current debates on failure as an aesthetic (...) category, eldritch Priest shows failure to be a duplicitous concept that traffics in paradox and sustains the conditions for magical thinking and hyperstition. Framing recent experimental composition as a deviant kind of sound art, Priest explores how the affective and formal elements of post-Cagean music couples with contemporary culture's themes of depression, distraction, and disinformation to create an esoteric reality composed of counterfactuals and pseudonymous beings. Ambitious in content and experimental in its approach, Boring Formless Nonsense will challenge and fracture your views on failure, creativity, and experimental music. (shrink)

Graham Priest presents an original exploration of questions concerning the one and the many. He covers a wide range of issues in metaphysics--unity, identity, grounding, mereology, universals, being, intentionality and nothingness--and draws on Western and Asian philosophy as well as paraconsistent logic to offer a radically new treatment of unity.

Priest (2009) formulates a propositional logic which, by employing the worldsemantics for intuitionist logic, has the same positive part but dualises the negation, to produce a paraconsistent logic which it calls 'Da Costa Logic'. This paper extends matters to the first-order case. The paper establishes various connections between first order da Costa logic, da Costa's own Cω, and classical logic. Tableau and natural deductions systems are provided and proved sound and complete.

This revised and considerably expanded 2nd edition brings together a wide range of topics, including modal, tense, conditional, intuitionist, many-valued, paraconsistent, relevant, and fuzzy logics. Part 1, on propositional logic, is the old Introduction, but contains much new material. Part 2 is entirely new, and covers quantification and identity for all the logics in Part 1. The material is unified by the underlying theme of world semantics. All of the topics are explained clearly using devices such as tableau proofs, and (...) their relation to current philosophical issues and debates are discussed. Students with a basic understanding of classical logic will find this book an invaluable introduction to an area that has become of central importance in both logic and philosophy. It will also interest people working in mathematics and computer science who wish to know about the area. (shrink)

There is at present a certain dispute about counterfactuals taking place. What is at issue is whether counterfactuals with necessarily false antecedents are all true. Some hold that such counterfactuals are vacuously true, appearances notwithstanding. Let us call such people vacuists. Others hold that some counterfactuals with necessarily false antecedents are true; some are false: it just depends on their contents. Let us call such people non-vacuists. As a notable representative of the vacuists, I will take Tim Williamson. On the (...) other side, I will take the position defended by Berto, French, Priest, and Ripley. I will argue (unsurprisingly) that the better choice is Non-Vacuism. That, however, is a subsidiary aim of this paper. The main point is to illustrate the method of theory-choice. (shrink)

The paper explains how a paraconsistent logician can appropriate all classical reasoning. This is to take consistency as a default assumption, and hence to work within those models of the theory at hand which are minimally inconsistent. The paper spells out the formal application of this strategy to one paraconsistent logic, first-order LP. (See, Ch. 5 of: G. Priest, In Contradiction, Nijhoff, 1987.) The result is a strong non-monotonic paraconsistent logic agreeing with classical logic in consistent situations. It is shown (...) that the logical closure of a theory under this logic is trivial only if its closure under LP is trivial. (shrink)

One of Da Costa’s motives when he constructed the paraconsistent logic C! was to dualise the negation of intuitionistic logic. In this paper I explore a different way of going about this task. A logic is defined by taking the Kripke semantics for intuitionistic logic, and dualising the truth conditions for negation. Various properties of the logic are established, including its relation to C!. Tableau and natural deduction systems for the logic are produced, as are appropriate algebraic structures. The paper (...) then investigates dualising the intuitionistic conditional in the same way. This establishes various connections between the logic, and a logic called in the literature ‘Brouwerian logic’ or ‘closed-set logic’. (shrink)

This is the first introductory textbook on non-classical propositional logics.

Literature in the epistemology of disagreement has focused on peer disagreement: disagreement between those with shared evidence and equal cognitive abilities. Additional literature focuses on the perspective of amateurs who disagree with experts. However, the appropriate epistemic reaction from superiors who disagree with inferiors remains underexplored. Prima facie, this may seem an uninteresting set of affairs. If A is B’s superior, and A has good reason to believe she is B’s superior, A appears free to dismiss B’s disagreement. However, a (...) closer look will show otherwise. I first distinguish competent from incompetent inferiors and then argue that disagreement from the former often gives superiors reason to adjust credence and reevaluate belief. In other words, epistemic inferiority alone is insufficient grounds for dismissing opinion. More nuanced difficulties arise with incompetent inferiors. When superiors disagree with incompetents, this might provide evidence to bolster belief credence; however, agreement from incompetents can defeat justification. In either instance, inferior opinion carries epistemic weight. Yet, this fails to cover all ground; at times, superiors learn nothing from inferior disagreement. I finish by exploring these uninformative disagreements, how to distinguish them from the informative cases, and the proper epistemic reactions thereof. (shrink)

The article looks at the structure of impossible worlds, and their deployment in the analysis of some intentional notions. In particular, it is argued that one can, in fact, conceive anything, whether or not it is impossible. Thus a semantics of conceivability requires impossible worlds.

The point of this paper is to bring together three topics: non-existent objects, mereology, and nothing. There are important inter-connections, which it is my aim to spell out, in the service of an account of the last of these.

My topic concerns the martial arts – or at least the East Asian martial arts, such as karatedo, taekwondo, kendo, wushu. To what extent what I have to say applies to other martial arts, such as boxing, silat, capoeira, I leave as an open question. I will illustrate much of what I have to say with reference to karatedo, since that is the art with which I am most familiar; but I am sure that matters are much the same with (...) other East Asian martial arts. (shrink)

The paper describes a new way of thinking about conditionals, in terms of information transfer between worlds. This way of looking at things provides an answer to some of the standard problems concerning conditionals, and undercuts the claim that indicative and subjunctive conditionals are distinct.

IntroductionCurry’s paradox is well known.See, e.g., Priest , ch. 6. It comes in both set theoretic and semantic versions. Here we will concentrate on the semantic versions. Historically, these have deployed the notion of truth. Those who wish to endorse an unrestricted T-schema have mainly endorsed a logic which rejects the principle of Absorption, \\models A\rightarrow B\). High profile logics of this kind are certain relevant logics; these have semantics which show how and why this principle is not valid. Of (...) more recent times, paradoxes which are clearly in the same family have been appearing; but these concern the notion of validity itself. The standard semantics of relevant logics seem powerless to address these. But they can. This note shows how. The upshot can be seen as a return to the roots of relevant logic, in a sense to become clear.BackgroundThe Usual Curry ParadoxesLet us start with a couple of standard forms of the paradox. I .. (shrink)

Many people hold that there is a distinctive notion of metaphysical necessity. In this paper I explain why I am skeptical about the view. I examine the sorts of considerations that are adduced for it, and argue that they meet equal and opposite considerations.

In this paper, I start by showing that sorites paradoxes are inclosure paradoxes. That is, they fit the Inclosure Scheme which characterizes the paradoxes of self-reference. Given that sorites and self-referential paradoxes are of the same kind, they should have the same kind of solution. The rest of the paper investigates what a dialetheic solution to sorites paradoxes is like, connections with a dialetheic solution to the self-referential paradoxes, and related issues—especially so called "higher order" vagueness.

This chapter argues that in the context of an account of meaning appropriate for dialetheism, Boolean negation is a meaningless notion.

The first half of this article is critical: it develops an interpretation of Kant as trying, and failing, to limit our judgments to phenomena and abstain from making claims about noumena, and an interpretation of Wittgenstein as trying, and failing, to develop a theory of meaning that abstains from attempting to say the unsayable. On the reading offered, both Kant and Wittgenstein find themselves saying things that by their own lights cannot be said: in Kant’s case, claims about noumena, and (...) in Wittgenstein’s case, structural claims. While Kant attempts a solution of the problem which also fails, Wittgenstein bites the bullet and leaves his Tractatus, for the most part, void and meaningless. The suggested response is a dialetheic approach—either as an alternative or, potentially, as an amendment to a Kantian or Wittgensteinian theory. According to this approach, certain problems in philosophy arise from true contradictions and thus require a theory that makes sense of contradiction. A subgroup of these problems (among them the noumenal and structural issues in Kant and Wittgenstein) are about things that both are and are not ineffable. The second half of the paper develops a dialetheic account of ineffability and a concise formal theory to ensure that contradiction at the limits of language does not spread to other areas. (shrink)

Imre Lakatos’ Proofs and Refutations is a book well known to those who work in the philosophy of mathematics, though it is perhaps not widely referred to. Its general thrust is out of tenor with the foundationalist perspective that has dominated work in the philosophy of mathematics since the early years of the 20th century. It seems to us, though, that the book contains striking insights into the nature of proof, and the purpose of this paper is to explore and (...) apply some of these. (shrink)