After sketching an argument for radical anti-realism that does not appeal to human limitations but polynomial-time computability in its definition of feasibility, I revisit an argument by Wittgenstein on the surveyability of proofs, and then examine the consequences of its application to the notion of canonical proof in contemporary proof-theoretical-semantics.

This volume examines the concept of falsification as a central notion of semantic theories and its effects on logical laws. The point of departure is the general constructivist line of argument that Michael Dummett has offered over the last decades. From there, the author examines the ways in which falsifications can enter into a constructivist semantics, displays the full spectrum of options, and discusses the logical systems most suitable to each one of them. While the idea of introducing falsifications into (...) the semantic account is Dummett's own, the many ways in which falsificationism departs quite radically from verificationism are here spelled out in detail for the first time. The volume is divided into three large parts. The first part provides important background information about Dummett’s program, intuitionism and logics with gaps and gluts. The second part is devoted to the introduction of falsifications into the constructive account and shows that there is more than one way in which one can do this. The third part details the logical effects of these various moves. In the end, the book shows that the constructive path may branch in different directions: towards intuitionistic logic, dual intuitionistic logic and several variations of Nelson logics. The author argues that, on balance, the latter are the more promising routes to take. "Kapsner’s book is the first detailed investigation of how to incorporate the notion of falsification into formal logic. This is a fascinating logico-philosophical investigation, which will interest non-classical logicians of all stripes." Graham Priest, Graduate Center, City University of New York and University of Melbourne. (shrink)

I argue that the standard anti-realist argument from manifestability to intuitionistic logic is either unsound or invalid. Strong interpretations of the manifestability of understanding are falsified by the existence of blindspots for knowledge. Weaker interpretations are either too weak, or gerrymandered and ad hoc. Either way, they present no threat to classical logic.

This paper is concerned with the relationship between the metaphysical doctrine of realism about the external world and semantic realism, as characterised by Michael Dummett. I argue that Dummett's conception of the relationship is flawed, and that Crispin Wright's account of the relationship, although designed to avoid the problems which beset Dummett's, nevertheless fails for similar reasons. I then aim to show that despite the fact that Dummett and Wright both fail to give a plausible account of the relationship between (...) semantic realism and the metaphysical doctrine of realism, the semantic issue and the metaphysical issue are importantly related. I outline the precise sense in which the evaluation of semantic realism is relevant to the evaluation of realism about the external world, a sense overlooked by opponents of Dummett, such as Simon Blackburn and Michael Devitt. I finish with some brief remarks on metaphysics, semantics, and the nature of philosophy, and suggest that Dummett's arguments against semantic realism can retain their relevance to metaphysical debate even if we reject Dummett's idea that the theory of meaning is thefoundation of all philosophy. (shrink)