Putnam and Finkelstein have proposed the abandonment of distributivity in the logic of quantum theory. This change results from defining the connectives, not truth-functionally, but in terms of a certain empirical ordering of propositions. Putnam has argued that the use of this ordering ("implication") to govern proofs resolves certain paradoxes. But his resolutions are faulty; and in any case, the paradoxes may be resolved with no changes in logic. There is therefore no reason to regard the partially ordered set of (...) propositions as a logic--i.e. as embodying a criterion for soundness of proofs. Its role in quantum theory ought to be understood in an entirely different way. (shrink)

Recently, there has been a significant upsurge of interest in what has come to be known as the 'Adoption Problem', first developed by Saul Kripke in 1974. The problem purports to raise a difficulty for Quine’s anti-exceptionalist conception of logic. In what follows, we first offer a statement of the problem and argue that, so understood, it depends upon natural but resistible assumptions. We then use that discussion as a springboard for developing a different adoption problem, arguing that, for a (...) significant class of basic logical principles, there is indeed a difficulty in seeing how they might be ‘freely adopted,’ thereby vindicating something close to the spirit of Kripke’s original claim. This first part of our argument will enforce a significant qualification of Quine’s claim that basic logical principles can be empirically confirmed. In the concluding sections of the paper, we turn to the question, specifically, of the empirical revisability of logic, arguing that when proper attention is paid to the role of reasoning in theory revision, it does indeed emerge that anti-exceptionalism, in full generality, is untenable. (shrink)

After introducing the adoption problem (AP) as the claim that certain basic logical principles cannot be adopted, I offer a characterization of this notion as a two-phase process consisting in (1) the acceptance of a basic logical principle, and (2) the development, in virtue of Phase 1, of a practice of inferring in accordance with that principle. The case of a subject who does not infer in accordance with universal instantiation is considered in detail. I argue that the AP has (...) deep and wide implications for the epistemology of logic, extending well beyond Kripke’s original target, viz. Putnam’s proposal for the empirical revision of logic and its background Quinean epistemology. In particular, the AP questions whether basic logical principles could have a fundamental role in our inferential practices, drawing our attention to the nature of basic inferences and the need to have a clearer conception of them before taking a stand on the matter of the epistemic justification of the logical principles. (shrink)

Can we change our logic and if so how? In ‘The Question of Logic’ (this volume), Saul Kripke takes a certain message about this from Lewis Carroll’s famous pape.

Many advocates of non-classical logic for reasons external to mathematics claim that their proposed revisions are consistent with the use of classical logic within pure mathematics. Doubts are raised about such claims, concerning the applicability of pure mathematics to natural and social science. -/- .

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)