We consider notions of truth and logical validity defined in various recent constructions of Hartry Field. We try to explicate his notion of determinate truth by clarifying the path-dependent hierarchies of his determinateness operator.

In this paper I examine a cluster of concepts relevant to the methodology of truth theories: 'informative definition', 'recursive method', 'semantic structure', 'logical form', 'compositionality', etc. The interrelations between these concepts, I will try to show, are more intricate and multi-dimensional than commonly assumed.

This is a collection of essays about logic and its applications to various philosophical problems. In general, it is argued that logic constitutes an important device of philosophical analysis. Concerning the nature of logic the author defends the thesis that first-order logic is the logic. Among the philosophical problems to which logic is applied in the essays are: truth, consistency, realism, foundations of semantics, psychologism, undetermination of theories by empirical data, modalities, value concepts, (...) identity, vagueness, God's existence, transcendentals, legal reasoning, category mistakes, bivalence, the cognitive relation, and meaningfulness. (shrink)

A team of 36 leading experts present the definitive guide to philosophical issues to do with truth. They survey how the concept of truth has been understood from antiquity to the present; offer critical assessments of the standard theories of truth; and explore the role of truth in logic, language, metaphysics, ethics, science, and mathematics.

This paper offers a discussion of metaphysical pluralism, alethic pluralism, and logical pluralism. According to the metaphysical pluralist, there are several ways of being. According to the alethic pluralist, there are several ways of being true, and according to the logical pluralist, there are several ways of being valid. Each of these three forms of pluralism will be considered on its own, but the ambition of the paper is to explore possible connections between them. My primary objective is to present (...) and develop a positive account according to which the different forms of pluralism are intimately related. I will proceed in two steps. First, I will investigate the connection between alethic pluralism and logical pluralism. I will argue that a certain version of alethic pluralism supports logical pluralism. Second, I will connect alethic pluralism and logical pluralism to metaphysical pluralism. I will suggest that the former two are at least partly founded on the latter. (shrink)

Thomas Hofweber takes the semantic paradoxes to motivate a radical reconceptualization of logical validity, rejecting the idea that an inference rule is valid just in case every instance thereof is necessarily truth-preserving. Rather than this “strict validity”, we should identify validity with “generic validity”, where a rule is generically valid just in case its instances are truth preserving, and where this last sentence is a generic, like “Bears are dangerous”. While sympathetic to Hofweber’s view that strict validity should (...) be replaced by something allowing for exceptions, I argue that this should instead be truth-conduciveness, a matter of a large majority of instances being truth-preserving. The fact that inference rules have uncountably many instances, I argue, can be handled by defining truth-conduciveness as relative to finite sets of instances. Moreover, I argue that Hofweber’s position, while seemingly radical, may be less so under closer scrutiny. For the mere claim that classical rules and unrestricted truth rules are generically valid (or truth-conducive) is not in itself controversial. Also, if there is an answer to the question of which of these are also strictly valid, then the claim that generic validity is the central notion in logic is at most an interest-relative matter, since there is then also a fact of the matter as to which inference rules are (not) strictly valid. If no solution operating with strict validity to the paradoxes can be had, however, then the claim that validity should be identified with a weaker notion is better motivated. I argue that it is reasonable, in view of past failures, to conjecture that no ordinary solution will score high enough relative to standard (uncontroversial) desiderata to merit justified belief. Hence, it is unknowable which solution is correct. I further argue that this is best explained by its being metaphysically indeterminate which solution is correct. If this conjecture is true, then we ought instead to think of validity as allowing exceptions, and then take the “true logic” to be one that takes both the classical rules and the truth rules to be valid, i.e., truth-conducive. This logic scores very high on the desiderata on logics, and is therefore preferable to any logic operating with strict validity. (shrink)

An exact truthmaker for A is a state which, as well as guaranteeing A’s truth, is wholly relevant to it. States with parts irrelevant to whether A is true do not count as exact truthmakers for A. Giving semantics in this way produces a very unusual consequence relation, on which conjunctions do not entail their conjuncts. This feature makes the resulting logic highly unusual. In this paper, we set out formal semantics for exact truthmaking and characterise the resulting (...) notion of entailment, showing that it is compact and decidable. We then investigate the effect of various restrictions on the semantics. We also formulate a sequent-style proof system for exact entailment and give soundness and completeness results. (shrink)

The aim of this paper is twofold: first, I provide a cluster of theories of truth in classical logic that is (internally) consistent with global reflection principles: the theories of positive truth (and falsity). After that, I analyse the _epistemic value_ of such theories. I do so employing the framework of cognitive projects introduced by Wright (Proc Aristot Soc 78:167–245, 2004), and employed—in the context of theories of truth—by Fischer et al. (Noûs 2019. https://doi.org/10.1111/nous.12292 ). In (...) particular, I will argue that theories of positive truth are _trustworthy_, analogously to the theories of full disquotational truth. Moreover, I argue that, for a given cognitive project, _if_ the acceptance of trustworthy theories is taken to be an _epistemic norm_ of cognitive project, then one has good reasons to accept theories of positive truth over other rival theories of truth in classical logic. On the other hand, the latter theories are deemed epistemically unacceptable. (shrink)

Three leading philosopher-logicians present a clear and concise overview of formal theories of truth, explaining key logical techniques. Truth is as central topic in philosophy: formal theories study the connections between truth and logic, including the intriguing challenges presented by paradoxes like the Liar.

This book tackles the issues that arise in connection with intensional logic -- a formal system for representing and explaining the apparent failures of certain important principles of inference such as the substitution of identicals and existential generalization -- and intentional states --mental states such as beliefs, hopes, and desires that are directed towards the world. The theory offers a unified explanation of the various kinds of inferential failures associated with intensional logic but also unifies the study of (...) intensional contexts and intentional states by grounding the explanation of both phenomena in a single theory. When an axiomatized realm of abstract entities is added to the metaphysical structure of the world, we can use them to identify and individuate the contents of directed mental states. The special abstract entities can be viewed as the objectified contents of mental files, and they play a crucial role in the analysis of truth conditions of the sentences involved in inferential failures. (shrink)

The First International Workshop brings together researchers from the theoretical ends of the logic programming and artificial intelligence communities to discuss their mutual interests. Logic programming deals with the use of models of mathematical logic as a way of programming computers, where theoretical AI deals with abstract issues in modeling and representing human knowledge and beliefs. One common ground is nonmonotonic reasoning, a family of logics that includes room for the kinds of variations that can be found (...) in human reasoning. Topics covered: Stable Semantics. Default Logic. AutoEpistemic Logic. Truth Maintenance Systems. Implementation Issues. Diagnosis. Applications. Inheritance Reasoning. Logics of Belief. Inconsistency and Non-Monotonicity. (shrink)

The present author developed a calculus for the logic of ‘because’. In a recent paper in this journal, it has been claimed that the central inference rules for the logic are invalid and that the intuition upon which the rules are based is not accounted for. This note criticises these arguments and presents an independent argument in favour of the rules used in the logic.

Needs, Values, Truth brings together of some of the most important and influential writings by a leading contemporary philosopher, drawn from twenty-five years of his work in the broad area of the philosophy of value. The author ranges between problems of ethics, meta-ethics, philosophy of mind, and philosophy of logic and language, looking at questions relating to meaning, truth and objectivity in judgements of value. For this third edition he has added a new essay on incommensurability, in (...) addition to making minor revisions to the existing text. The volume will stand as a definitive summation of his work in this area. (shrink)

In this rigorous investigation into the logic of truth Anil Gupta and Nuel Belnap explain how the concept of truth works in both ordinary and pathological..

A note correcting some technical terminology from linguistics found in ‘Distributive Terms, Truth, and The Port Royal Logic’, this journal, Jan. 17, 2013, 133–54.

This chapter explores the intersection of experimental philosophy and philosophical logic. It considers a distinction between pure and applied logic. It sketches some ways in which experimental results and empirical results more broadly, can inform and have informed debates within philosophical logic. The chapter lays out a way of looking at the situation that makes plain at least one way in which people should expect experimental and logical concerns to overlap. It turns to the phenomenon of vagueness, (...) where people can see this overlap explored and developed from multiple angles, showing just how intimately related experiment and logic can be. Logic is not only useful for exploring hypotheses about truth conditions and entailments but also for exploring hypotheses about reasoning. Logical and experiment can fruitfully interact in a variety of applications, and that is all people need for experimental philosophical logic to be worthwhile. (shrink)

This book on modal logic is especially designed for philosophy students. It provides an accessible yet technically sound treatment of modal logic and its philosophical applications. Every effort is made to simplify the presentation by using diagrams instead of more complex mathematical apparatus. These and other innovations provide philosophers with easy access to a rich variety of topics in modal logic, including a full coverage of quantified modal logic, non-rigid designators, definite descriptions, and the de-re de-dicto (...) distinction. Discussion of philosophical issues concerning the development of modal logic is woven into the text. The book uses natural deduction systems, which are widely regarded as the easiest to teach and use. It also includes a diagram technique that extends the method of truth trees to modal logic. This provides a foundation for a novel method for showing completeness that is easy to extend to quantifiers. This second edition contains a new chapter on logics of conditionals, an updated and expanded bibliography, and is updated throughout. (shrink)

We represent truth sets for a variety of the well known semantic theories of truth as those sets consisting of all sentences for which a player has a winning strategy in an infinite two person game. The classifications of the games considered here are simple, those over the natural model of arithmetic being all within the arithmetical class of $\Sum_{3}^{0}$.

There is a long-standing disagreement among Branching-Time theorists. Even though they all believe that the branching representation accurately grasps the idea that the future, contrary to the past, is open, they argue whether this representation is compatible with the claim that one among many possible futures is distinguished—the single future that will come to be. This disagreement is paralleled in an argument about the bivalence of future contingents. The single, privileged future is often called the Thin Red Line. I reconstruct (...) the history of the arguments for and against this idea. Then, I propose my own version of the Thin Red Line theory which is immune to the major objections found in the literature. I argue that the semantic disagreement is grounded in distinct metaphysical presuppositions. My solution is expressed in a conceptual framework proposed by John MacFarlane, who distinguishes semantics from postsemantics. I extend his distinction and introduce a new notion of presemantics to elucidate my idea. (shrink)

The present study reiterates one of the main ideas that we exposed in 1983, in the paper “Din fals rezultă orice” (“From False Follows Anything”), published in the volume Întemeieri raţionale în filosofia ştiinţei (Rational Foundations in the Philosophy of Science) when we referred to the notion of semi-truth, as a third alethic value, placed between „truth” and „falsehood”, thus contributing to the functionality of the trivalent logic. Now we analyze the conceptions of Petre Botezatu, Mario Bunge, (...) Karl R. Popper and Nicholas Rescher, in order to argue that it is important not to identify the epistemological term „probable” (= uncertain) with the semantic term „partial” or „approximate”, when we speak about the concept of truth. (shrink)

This book examines the complex and varied ways in which fictions relate to the real world, and offers a precise account of how imaginative works of literature can use fictional content to explore matters of universal human interest. While rejecting the traditional view that literature is important for the truths that it imparts, the authors also reject attempts to cut literature off altogether from real human concerns. Their detailed account of fictionality, mimesis, and cognitive value, founded on the methods of (...) analytical philosophy, restores to literature its distinctive status among cultural practices. The authors also explore metaphysical and skeptical views, prevalent in modern thought, according to which the world itself is a kind of fiction, and truth no more than a social construct. They identify different conceptions of fiction in science, logic, epistemology, and make-believe, and thereby challenge the idea that discourse per se is fictional and that different modes of discourse are at root indistinguishable. They offer rigorous analyses of the roles of narrative, imagination, metaphor, and "making" in human thought processes. Both in their methods and in their conclusions, Lamarque and Olsen aim to restore rigor and clarity to debates about the values of literature, and to provide new, philosophically sound foundations for a genuine change of direction in literary theorizing. (shrink)

Given Heidegger’s inflammatory remarks about the intellectual poverty of modern logic, it may come as a surprise to be told that he has something to contribute to the philosophy of logic. One of the rewards of Daniel Dahlstrom’s Heidegger’s Concept of Truth is its argument that Heidegger can illuminate such issues in the philosophy of logic as the character of propositions, the nature of bivalence, and the concept of truth. Dahlstrom focuses on Heidegger’s work in (...) the years immediately before and after the publication of Being and Time, with particular emphasis on the lecture courses from this period, especially the one published as Logik: Die Frage nach der Wahrheit. (shrink)

By a classical result of Kotlarski, Krajewski and Lachlan, pathological satisfaction classes can be constructed for countable, recursively saturated models of Peano arithmetic. In this paper we consider the question of whether the pathology can be eliminated; we ask in effect what generalities involving the notion of truth can be obtained in a deflationary truth theory (a theory of truth which is conservative over its base). It is shown that the answer depends on the notion of pathology (...) we adopt. It turns out in particular that a certain natural closure condition imposed on a satisfaction class—namely, closure of truth under sentential proofs—generates a nonconservative extension of a syntactic base theory (Peano arithmetic). (shrink)

This is one of those cases to which Dr. 8 oodhouse's remark applies with all its force, that a method which leads to true results must have its logic — H.S Smith (" On Some of the Methods at Present in Use in Pure Geometry," p. 6) A goodly amount of modern metaphysics has concerned itself, in one form or another, with the question: what attitude should we take in regard to a language whose semantic underpinnings seem less than (...) certain? Since much of standard English is surely of this type, many philosophers have felt driven to extreme and unpalatable resolutions — wholesale rejection of attractive logical rules, radical "antirealism", "minimalism" about truth, and so forth, Scientists, however, have long dealt with analogous foundational insecurities and, under the duress of practicality, have framed a set of shifting attitudes towards language and reasoning that seem far more commonsensical than the extreme positions to which pure philosophy has often been led. Following this lead, this essay will recommend a more nuanced approach to linguistic insecurity that is neither naively optimistic nor mired in the gloomy sloughs of antirealism. (shrink)

In 1986, Mikenberg et al. introduced the semantic notion of quasi-truth defined by means of partial structures. In such structures, the predicates are seen as triples of pairwise disjoint sets: the set of tuples which satisfies, does not satisfy and can satisfy or not the predicate, respectively. The syntactical counterpart of the logic of partial truth is a rather complicated first-order modal logic. In the present article, the notion of predicates as triples is recursively extended, in (...) a natural way, to any complex formula of the first-order object language. From this, a new definition of quasi-truth is obtained. The proof-theoretic counterpart of the new semantics is a first-order paraconsistent logic whose propositional base is a 3-valued logic belonging to hierarchy of paraconsistent logics known as Logics of Formal Inconsistency, which was proposed by Carnielli and Marcos in 2002. (shrink)

Designed for use by philosophy students, this 2006 book provides an accessible, yet technically sound treatment of modal logic and its philosophical applications. Every effort has been made to simplify the presentation by using diagrams in place of more complex mathematical apparatus. These and other innovations provide philosophers with easy access to a rich variety of topics in modal logic, including a full coverage of quantified modal logic, non-rigid designators, definite descriptions, and the de-re de-dictio distinction. Discussion (...) of philosophical issues concerning the development of modal logic is woven into the text. The book uses natural deduction systems and also includes a diagram technique that extends the method of truth trees to modal logic. This feature provides a foundation for a novel method for showing completeness, one that is easy to extend to systems that include quantifiers. (shrink)

We show that the set of ultimately true sentences in Hartry Field's Revenge-immune solution model to the semantic paradoxes is recursively isomorphic to the set of stably true sentences obtained in Hans Herzberger's revision sequence starting from the null hypothesis. We further remark that this shows that a substantial subsystem of second-order number theory is needed to establish the semantic values of sentences in Field's relative consistency proof of his theory over the ground model of the standard natural numbers: -CA0 (...) (second-order number theory with a -comprehension axiom scheme) is insufficient. We briefly consider his claim to have produced a solution to the semantic paradoxes by introducing this conditional. We remark that the notion of a operator can be introduced in other settings. (shrink)

Published with the aid of a grant from the National Endowment for the Humanities. Contains the only complete English-language text of The Concept of Truth in Formalized Languages. Tarski made extensive corrections and revisions of the original translations for this edition, along with new historical remarks. It includes a new preface and a new analytical index for use by philosophers and linguists as well as by historians of mathematics and philosophy.

Shramko [. Truth, falsehood, information and beyond: The American plan generalized. In K. Bimbo, J. Michael Dunn on information based logics, outstanding contributions to logic...

In a recent paper, Philip Kremer proposes a formal and theory-relative desideratum for theories of truth that is spelled out in terms of the notion of ‘no vicious reference’. Kremer’s Modified Gupta-Belnap Desideratum (MGBD) reads as follows: if theory of truth T dictates that there is no vicious reference in ground model M, then T should dictate that truth behaves like a classical concept in M. In this paper, we suggest an alternative desideratum (AD): if theory of (...) truth T dictates that there is no vicious reference in ground model M, then T should dictate that all T-biconditionals are (strongly) assertible in M. We illustrate that MGBD and AD are not equivalent by means of a Generalized Strong Kleene theory of truth and we argue that AD is preferable over MGBD as a desideratum for theories of truth. (shrink)

This paper outlines a truth-conditional view of logical form, that is, a view according to which logical form is essentially a matter of truth-conditions. The main motivation for the view is a fact that seems crucial to logic. As _§_1 suggests, fundamental logical relations such as entailment or contradiction can formally be explained only if truth-conditions are formally represented.§2 spells out the view. _§_3 dwells on its anity with a conception of logical form that has been (...) defended in the past. _§§_4-6 draw attention to its impact on three major issues that concern, respectively, the extension of the domain of formal explanation, the semantics of tensed discourse, and the analysis of quantication. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:BOOK REVIEWS The Logic of God Incarnate. By THOMAS V. MORRIS. Ithaca: Cornell University Press, 1986. Pp. 220. $19.95. Thomas V. Morris, Assistant Professor of Philosophy at the University of Notre Dame, has written a technical yet provocative study on the Incarnation. As a faithful Christian he believes in and desires to defend the traditional Christian doctrine of the Incarnation proclaimed in the New Testament and defined by (...) the early councils of the Church, especially Chalcedon, that is, that Jesus is the One eternal Son existing in two natures. He also holds that, while the truth of the Incarnation is revealed, it must nonetheless stand the test of logic and reason. The Incarnation cannot be illogicaJ or meaningless. " If the church has been guided by God in such matters as the formulation of its creeds, conciliar decrees, and catechisms,.... we would not expect glaring logical flaws in its central doctrinal affirmations" (p. 46). The stated purpose of Morris's study is to defend the traditional doctrine against those who would hold it to be logically incoherent and meaningless. "In the course of thinking about the Incarnation for some years now, I have come to see that a few simple metaphysical distinctions and a solid dose of logical care will suffice to explicate and defend the doctrine against all extant criticisms of a philosophical nature" (p. 9). Morris meticulously analyzes and critiques a number of arguments that oppose the possibility of coherence of the Incarnation by attempting to demonstrate that such arguments are.either false and illogical themselves, or that they do not apply to a true understanding of the Incarnation. Moreover, Morris proposes a novel understanding of the Incarnation which he believes is both logical and intelligible, and which conforms to the Christian tradition. This goal of upholding the intelligibility of the Incarnate leads Morris to a three-fold task. He first of all must refute his chief adversaries, those who would deny the sensibleness of saying God became man in Jesus. Such critics deny the validity of the Incarnation on the ground..'! that it is meaning·less, and the'l'efore impossible to juxtapose the incommensurable. attributes of divinity and humanity, e.g., perfection/imperfection, immutability/corruptibility. They hold that Jesus could not have had both these sets of properties at once (cf. p. 20). Morris refuses to capitulate to such arguments. He nevertheless insists that any solution to the issue which would undermine human logic or which would fail to uphold the Christian's belief is no solution at all (cf. p. 32). 367 368 BOOK REVIEWS Secondly, Morris's task leads him to refute any attempts at a " OneNature " solution, which would "squash" together the human and divine natures in Jesus to form a single nature. Such proposals jeopardize either the integrity of Jesus's divinity (Arianism) or his humanity (Docetism, Monophysitism), inevitably composing a mythical tertium quid (cf. pp. 33-38). Morris presents a clear case against such corruptions of the Incarnation. Thirdly, Morris's task brings him to analyze contemporary kenotic Christology. He thoroughly discusses this approach, for the reason that it is directly involved in the issue at hand, namely, the incompatibility between divine and human properties in Christ. Secondarily, however, Morris's interest in kenoticism reflects his own hope that some variation of the approach might posibly arrive at a Christological solution (cf. p. 92). While he ultimately rejects kenoticism, Morris flirts with the various alternatives, and, as we shall see, his own perception of the Incarnation remains tinged with a kenotic flavor. How then is it possible to predicate of one and the same individual divine and human attributes intelligibly and coherentlyT To use contemporary computer jargon, the question might be phrased: is it possible that God and man can he "incarnation-friendly¥" Morris believes so. Morris first of all sets out to define the terms-divine nature and human nature. He believes part of the incompatibility problem lies in attributing to Jesus's humanity unnecessarily hostile aspects. He distinguishes between being "merely human" and being "fully human"· To be " merely human " is to possess not only those properties that narrowly define one's nature or kind, such as rationality, but... (shrink)

Methods available for the axiomatization of arbitrary finite-valued logics can be applied to obtain sound and complete intelim rules for all truth-functional connectives of classical logic including the Sheffer stroke and Peirce’s arrow. The restriction to a single conclusion in standard systems of natural deduction requires the introduction of additional rules to make the resulting systems complete; these rules are nevertheless still simple and correspond straightforwardly to the classical absurdity rule. Omitting these rules results in systems for intuitionistic (...) versions of the connectives in question. (shrink)

Logic and truth -- Inferences : assessment, recognition, and reconstruction -- Categorical statements and inferences -- Truth-functional statements -- Truth tables and proofs -- Natural deduction -- The logic of quantifiers -- Logic and language -- Applied inductive analysis.

Monists say that the nature of truth is invariant, whichever sentence you consider; pluralists say that the nature of truth varies between different sets of sentences. The orthodoxy is that logic and logical form favour monism: there must be a single property that is preserved in any valid inference; and any truth-functional complex must be true in the same way as its components. The orthodoxy, I argue, is mistaken. Logic and logical form impose only structural (...) constraints on a metaphysics of truth. Monistic theories are not guaranteed to satisfy these constraints, and there is a pluralistic theory that does so. (shrink)

Developing a suggestion of Wittgenstein, I provide an account of truth tables as formulas of a formal language. I define the syntax and semantics of TPL (the language of Tabular Propositional Logic), and develop its proof theory. Single formulas of TPL, and finite groups of formulas with the same top row and TF matrix (depiction of possible valuations), are able to serve as their own proofs with respect to metalogical properties of interest. The situation is different, however, for (...) groups of formulas whose top rows differ. For them I provide (i) a tree-style system of ‘row tree proofs’, which is shown to be sound and complete, and (ii) an alternative, re-writing strategy. (shrink)

In a forthcoming paper, Walter Carnielli and Abilio Rodrigues propose a Basic Logic of Evidence whose natural deduction rules are thought of as preserving evidence instead of truth. BLE turns out to be equivalent to Nelson’s paraconsistent logic N4, resulting from adding strong negation to Intuitionistic logic without Intuitionistic negation. The Carnielli/Rodrigues understanding of evidence is informal. Here we provide a formal alternative, using justification logic. First we introduce a modal logic, KX4, in which (...) \ can be read as asserting there is implicit evidence for X, where we understand evidence to permit contradictions. We show BLE embeds into KX4 in the same way that Intuitionistic logic embeds into S4. Then we formulate a new justification logic, JX4, in which the implicit evidence motivating KX4 is made explicit. KX4 embeds into JX4 via a realization theorem. Thus BLE has both implicit and explicit possibly contradictory evidence interpretations in a formal sense. (shrink)

This chapter attempts to give a brief overview of nonclassical (-logic) theories of truth. Due to space limitations, we follow a victory-through-sacrifice policy: sacrifice details in exchange for clarity of big-picture ideas. This policy results in our giving all-too-brief treatment to certain topics that have dominated discussion in the non-classical-logic area of truth studies. (This is particularly so of the ‘suitable conditoinal’ issue: §4.3.) Still, we present enough representative ideas that one may fruitfully turn from this (...) essay to the more-detailed cited works for further study. Throughout – again, due to space – we focus only on the most central motivation for standard non-classical-logic-based truth theories: namely, truth-theoretic paradox (specifically, due to space, the liar paradox). (shrink)

Bringing elementary logic out of the academic darkness into the light of day, Paul Tomassi makes logic fully accessible for anyone attempting to come to grips with the complexities of this challenging subject. Including student-friendly exercises, illustrations, summaries and a glossary of terms, _Logic_ introduces and explains: * The Theory of Validity * The Language of Propositional Logic * Proof-Theory for Propositional Logic * Formal Semantics for Propositional Logic including the Truth-Tree Method * The (...) Language of Quantificational Logic including the Theory of Descriptions. _Logic _is an ideal textbook for any logic student: perfect for revision, staying on top of coursework or for anyone wanting to learn about the subject. Related downloadable software for Macs and PCs is available for this title at www.logic.routledge.com. (shrink)

The author describes an interpreted modal language and produces some clear examples of logical and analytic truths that are not necessary. These examples: (a) are far simpler than the ones cited in the literature, (b) show that a popular conception of logical truth in modal languages is incorrect, and (c) show that there are contingent truths knowable ``a priori'' that do not depend on fixing the reference of a term.

This paper contends that Stoic logic (i.e. Stoic analysis) deserves more attention from contemporary logicians. It sets out how, compared with contemporary propositional calculi, Stoic analysis is closest to methods of backward proof search for Gentzen-inspired substructural sequent logics, as they have been developed in logic programming and structural proof theory, and produces its proof search calculus in tree form. It shows how multiple similarities to Gentzen sequent systems combine with intriguing dissimilarities that may enrich contemporary discussion. Much (...) of Stoic logic appears surprisingly modern: a recursively formulated syntax with some truth-functional propositional operators; analogues to cut rules, axiom schemata and Gentzen’s negation-introduction rules; an implicit variable-sharing principle and deliberate rejection of Thinning and avoidance of paradoxes of implication. These latter features mark the system out as a relevance logic, where the absence of duals for its left and right introduction rules puts it in the vicinity of McCall’s connexive logic. Methodologically, the choice of meticulously formulated meta-logical rules in lieu of axiom and inference schemata absorbs some structural rules and results in an economical, precise and elegant system that values decidability over completeness. (shrink)