Ian Rumfitt

Many prominent writers on the philosophy of logic, including Michael Dummett, Dag Prawitz, Neil Tennant, have held that the introduction and elimination rules of a logical connective must be ‘in harmony ’ if the connective is to possess a sense. This Harmony Thesis has been used to justify the choice of logic: in particular, supposed violations of it by the classical rules for negation have been the basis for arguments for switching from classical to intuitionistic logic. The Thesis has also had an influence on the philosophy of language: some prominent writers in that area, notably Dummett and Robert Brandom, have taken it to be a special case of a more general requirement that the grounds for asserting a statement must cohere with its consequences. This essay considers various ways of making the Harmony Thesis precise and scrutinizes the most influential arguments for it. The verdict is negative: all the extant arguments for the Thesis are weak, and no version of it is remotely plausible.

The paper addresses itself to the "Homeric struggle" in the theory of meaning between those (e.g., Grice) who try to analyze declarative meaning in terms of an intention to induce a belief and those (e.g., Davidson) for who declarative meaning consists in truth conditions. (The point of departure is Strawson's celebrated discussion of this issue, in his Inaugural Lecture.) I argue that neither style of analysis is satisfactory, and develop a "hybrid" that may be-although what I take from the Gricean side in the struggle is not the notion of an intention, but that of somebody's reason for speaking as he does. The paper applies the hybrid analysis to resolve certain problems connected with the rationale for compositional, truth-theoretic semantics

In developing his alternative, Brandom starts from a version of inferential-role semantics according to which an assertion's content is constituted by its place in a field of inferential relations. It is because we have "an independent theoretical grip on the notion of an inference", and of its goodness or badness, that we are able to attain a notion of content that is prior to any of the representational concepts. He stresses that the relevant assessment of inferences is not whether they are logically valid, but whether they are "materially correct," in a sense that Sellars is said to have succeeded in explaining. "As examples, consider the inference from 'Pittsburgh is to the West of Philadelphia' to 'Philadelphia is to the East of Pittsburgh', the inference from 'Today is Wednesday' to 'Tomorrow is Thursday', and that from 'Lightning is seen now' to 'Thunder will be heard soon'. It is the contents of the concepts West and East that make the first a good inference... and the contents of the concepts lightning and thunder, as well as the temporal concepts, that underwrite the third". Subsentential contents are extracted from the sentential contents thereby identified using substitutional methods derived from Frege.

It seems beyond doubt that a thinker can come to know a conclusion by deducing it from premisses that he knows already, but philosophers have found it puzzling how a thinker could acquire knowledge in this way. Assuming a broadly externalist conception of knowledge, I explain why judgements competently deduced from known premisses are themselves knowledgeable. Assuming an exclusionary conception of judgeable content, I further explain how such judgements can be informative. (According to the exclusionary conception, which I develop from some remarks in Ramsey, a judgement's content is given by the hitherto live possibilities that it excludes or rules out.) I propose that the value of logic lies in its allowing us to combine different sources of knowledge, so that we can learn things that we could not learn from those sources individually. I conclude by arguing that while single-conclusion logics possess that value, multiple-conclusion logics do not.

This paper assesses the prospects of a pragmatist theory of content. I begin by criticising the theory presented in D.H. Mellor’s essay ‘Successful Semantics’. I then identify problems and lacunae in the pragmatist theory of meaning sketched in Chapter 13 of Dummett’s The Logical Basis of Metaphysics. The prospects are brighter, I contend, for a tempered pragmatism, in which the theory of content is permitted to draw upon irreducible notions of truth and falsity. I sketch the shape of such a theory and illustrate the role of its pragmatist elements by showing how they point towards a promising account of the truth conditions of indicative conditionals. A feature of the account is that it validates Modus Ponens whilst invalidating Modus Tollens.

In what does the sense of a sentential connective consist? Like many others, I hold that its sense lies in rules that govern deductions. In the present paper, however, I argue that a classical logician should take the relevant deductions to be arguments involving affirmative or negative answers to yes-or-no questions that contain the connective. An intuitionistic logician will differ in concentrating exclusively upon affirmative answers. I conclude by arguing that a well known intuitionistic criticism of classical logic fails if the answer "No" is accorded parity with the answer "Yes".

Book synopsis: The philosophy of modality investigates necessity and possibility, and related notions--are they objective features of mind-independent reality? If so, are they irreducible, or can modal facts be explained in other terms? This volume presents new work on modality by established leaders in the field and by up-and-coming philosophers. Between them, the papers address fundamental questions concerning realism and anti-realism about modality, the nature and basis of facts about what is possible and what is necessary, the nature of modal knowledge, modal logic and its relations to necessary existence and to counterfactual reasoning. The general introduction locates the individual contributions in the wider context of the contemporary discussion of the metaphysics and epistemology of modality

In his essay ‘“Wang’s Paradox”’, Crispin Wright proposes a solution to the Sorites Paradox (in particular, the form of it he calls the ‘Paradox of Sharp Boundaries’) that involves adopting intuitionistic logic when reasoning with vague predicates. He does not give a semantic theory which accounts for the validity of intuitionistic logic (and the invalidity of stronger logics) in that area. The present essay tentatively makes good the deficiency. By applying a theorem of Tarski, it shows that intuitionistic logic is the strongest logic that may be applied, given certain semantic assumptions about vague predicates. The essay ends with an inconclusive discussion of whether those semantic assumptions should be accepted.