Logic isn’t special. Its theories are continuous with science; its method continuous with scientific method. Logic isn’t a priori, nor are its truths analytic truths. Logical theories are revisable, and if they are revised, they are revised on the same grounds as scientific theories. These are the tenets of anti-exceptionalism about logic. The position is most famously defended by Quine, but has more recent advocates in Maddy, Priest, Russell, and Williamson. Although these authors agree on many methodological issues about logic, (...) they disagree about which logic anti-exceptionalism supports. Williamson uses an anti-exceptionalist argument to defend classical logic, while Priest claims that his anti-exceptionalism supports nonclassical logic. This paper argues that the disagreement is due to a difference in how the parties understand logical theories. Once we reject Williamson’s deflationary account of logical theories, the argument for classical logic is undercut. Instead an alternative account of logical theories is offered, on which logical pluralism is a plausible supplement to anti-exceptionalism. (shrink)

Logical pluralism is the view that different logics are equally appropriate, or equally correct. Logical relativism is a pluralism according to which validity and logical consequence are relative to something. Stewart Shapiro explores various such views. He argues that the question of meaning shift is itself context-sensitive and interest-relative.

What are people who disagree about logic disagreeing about? The paper argues that (in a wide range of cases) they are primarily disagreeing about how to regulate their degrees of belief. An analogy is drawn between beliefs about validity and beliefs about chance: both sorts of belief serve primarily to regulate degrees of belief about other matters, but in both cases the concepts have a kind of objectivity nonetheless.

In order to perfectly describe the world, it is not enough to speak truly. One must also use the right concepts - including the right logical concepts. One must use concepts that "carve at the joints", that give the world's "structure". There is an objectively correct way to "write the book of the world". Much of metaphysics, as traditionally conceived, is about the fundamental nature of reality; in the present terms, this is about the world's structure. Metametaphysics - inquiry into (...) the status of metaphysical questions - turns on structure. The question of whether ontological, causal, or modal questions are "substantive" is in large part a question of whether the world has ontological, causal, and modal structure - whether quantifiers, causal relations, and modal operators carve at the joints. (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..

Logical pluralism is the view that there is more than one correct logic. In this article, I explore what logical pluralism is, and what it entails, by: (i) distinguishing clearly between relativism about a particular domain and pluralism about that domain; (ii) distinguishing between a number of forms logical pluralism might take; (iii) attempting to distinguish between those versions of pluralism that are clearly true and those that are might be controversial; and (iv) surveying three prominent attempts to argue for (...) logical pluralism and evaluating them along the criteria provided by (ii) and (iii). (shrink)

The relative merits and demerits of historically prominent views such as the correspondence theory, coherentism, pragmatism, verificationism, and instrumentalism have been subject to much attention in the truth literature and have fueled the long-lived debate over which of these views is the most plausible one. While diverging in their specific philosophical commitments, adherents of these historically prominent views agree in at least one fundamental respect. They are all alethic monists. They all endorse the thesis that there is only one property (...) in virtue of which propositions can be true, and so, in this sense, take truth to be one. The truth pluralist, on the other hand, rejects this idea. There are several properties in virtue of which propositions can be true. The literature on truth pluralism has been growing steadily for the past twenty years. This volume, however, is the first of its kind—the first collection of papers focused specifically on pluralism about truth. Part I is dedicated to the development, investigation, and critical discussion of different forms of pluralism. An additional reason to look at truth pluralism with interest is the significant connections it bears to other debates in the truth literature—the debates concerning traditional theories of truth and the deflationism/inflationism divide being cases in hand. Parts II and III of the volume connect truth pluralism to these two debates. (shrink)

There are quite a few theses about logic that are in one way or another pluralist: they hold (i) that there is no uniquely correct logic, and (ii) that because of this, some or all debates about logic are illusory, or need to be somehow reconceived as not straightforwardly factual. Pluralist theses differ markedly over the reasons offered for there being no uniquely correct logic. Some such theses are more interesting than others, because they more radically affect how we are (...) initially inclined to understand debates about logic. Can one find a pluralist thesis that is high on the interest scale, and also true? (shrink)

Logical pluralism is the view according to which there is more than one relation of logical consequence, even within a given language. A recent articulation of this view has been developed in terms of quantification over different cases: classical logic emerges from consistent and complete cases; constructive logic from consistent and incomplete cases, and paraconsistent logic from inconsistent and complete cases. We argue that this formulation causes pluralism to collapse into either logical nihilism or logical universalism. In its place, we (...) propose a modalist account of logical pluralism that is independently well motivated and that avoids these collapses. (shrink)

We are pluralists about logical consequence [1]. We hold that there is more than one sense in which arguments may be deductively valid, that these senses are equally good, and equally deserving of the name deductive validity. Our pluralism starts with our analysis of consequence. This analysis of consequence is not idiosyncratic. We agree with Richard Jeffrey, and with many other philosophers of logic about how logical consequence is to be defined. To quote Jeffrey.

Intuitionists and classical logicians use in common a large number of the logical axioms, even though they supposedly mean different things by the logical connectives and quantifiers — conquans for short. But Wittgenstein says The meaning of a word is its use in the language. We prove that in a definite sense the intuitionistic axioms do indeed characterize the logical conquans, both for the intuitionist and the classical logician.

Consequence is at the heart of logic; an account of consequence, of what follows from what, offers a vital tool in the evaluation of arguments. Since philosophy itself proceeds by way of argument and inference, a clear view of what logical consequence amounts to is of central importance to the whole discipline. In this book JC Beall and Greg Restall present and defend what thay call logical pluralism, the view that there is more than one genuine deductive consequence relation, a (...) position which has profound implications for many linguists as well as for philosophers. We should not search for one true logic, since there are many. (shrink)

Introduction to this special issue of The Australasian Journal of Logic.

A survey of contemporary work on logical pluralism.

In this article, both Anaxagoras’ theory of multiple worlds and the principles of his theory of matter are examined. It is argued that the five principles, which are set out explicitly in the extant fragments, (No Becoming, Indefinite Types, Universal Mixture, Predominance, and Infinite Divisibility) form a consistent set. Further, it is argued that the principle of Homoeomereity, which Anaxagoras attributes to Anaxagoras, is consistent with Anaxagoras’ other principles and is likely to be a genuine principle of Anaxagoras’ physics.

In Truth as One and Many, Michael Lynch offers a new theory of truth. There are two kinds of theory of truth in the literature. On the one hand, we have logical theories, which seek to construct formal systems that are consistent, while also containing a predicate which have as many as possible of the properties which we ordinarily take the English predicate ‘is true’ to have; salient examples include Tarski’s and Kripke’s theories of truth. On the other hand, we (...) have metaphysical theories, which seek to give a non-formal account of the nature of truth – of what truth consists in, of what it means to say that something is true; salient examples include correspondence, coherence and deflationary theories of truth. Lynch’s theory – functionalism about truth – is of the second sort.The theory takes its start from a number of principles which Lynch classifies as truisms about truth:Objectivity: The belief that p is true if, and only if, with respect to the belief that p, things are as they are believed to be.Norm of Belief: It is prima facie correct to believe that p if and only if the proposition that p is true.End of Inquiry: Other things being equal, true beliefs are a worthy goal of inquiry.Lynch argues that other familiar principles can be derived from these: for example, Objectivity together with some auxiliary principles and definitions yields versions of the T-schema, and of the principle that beliefs can be true without being warranted and vice versa. These principles are supposed to give the nominal essence of truth – to constitute our folk theory of truth. Lynch …. (shrink)

A good argument is one whose conclusions follow from its premises; its conclusions are consequences of its premises. But in what sense do conclusions follow from premises? What is it for a conclusion to be a consequence of premises? Those questions, in many respects, are at the heart of logic (as a philosophical discipline). Consider the following argument: 1. If we charge high fees for university, only the rich will enroll. We charge high fees for university. Therefore, only the rich (...) will enroll. There are many different things one can say about this argument, but many agree that if we do not equivocate (if the terms mean the same thing in the premises and the conclusion) then the argument is valid, that is, the conclusion follows deductively from the premises. This does not mean that the conclusion is true. Perhaps the premises are not true. However, if the premises are true, then the conclusion is also true, as a matter of logic. This entry is about the relation between premises and conclusions in valid arguments. (shrink)

About twenty-five years ago, Charles Parsons published a paper that began by asking why we still discuss the Liar Paradox. Today, the question seems all the more apt. In the ensuing years we have seen not only Parsons’ work (1974), but seminal work of Saul Kripke (1975), and a huge number of other important papers. Too many to list. Surely, one of them must have solved it! In a way, most of them have. Most papers on the Liar Paradox offer (...) some explanation of the behavior of paradoxical sentences, and most also offer some extension for the predicate ‘true’ that they think is adequate, at least in some restricted setting. But if this is a solution, then the problem we face is far from a lack of solutions; rather, we have an overabundance of conflicting ones. Kripke’s work alone provides us with uncountably many different extensions for the truth predicate. Even if it so happens that one of these is a conclusive solution, we do not seem to know which one, or why. We should also ask, given that we are faced with many technically elegant but contradictory views, if they are really all addressing the same problem. What we lack is not solutions, but a way to compare and evaluate the many ones we have. (shrink)

This chapter distinguishes between various senses in which one might be a pluralist about logic. In several of these, pluralism is uncontentiously correct. The difficult issue is whether there are different accounts of validity that are equally correct. It argues for logical monism in this regard.