Wittgenstein on negation, material incompatibilities and inferential thickness

Marcos Silva

It is not hard to find philosophers who take negation to be associated with thevery possibility of rational discourse. The nature of negation occupiesWittgenstein’s attention in his Notebooks1914 -16. His Tractatus (1921) addressesnegation as a formal operator related to the possibility of meaningful discourse. By 1929, after the full acknowledgment of the color -exclusionproblem, he admits that the material incompatibilities presented in certainconceptual systems cannot be reduced to formal tautologies and contradictions. Wittgensteinthen, in his middle period, has to examine the kind of negation that colorsystems should render, which expose, not just one, but several, or in somecases, infinite alternative propositions. In this paper, inspired by Brandom’sinferentialism (1994, 2000 e 2008), I explore the idea that Wittgenstein, inhis middle period, advocated a form of inferentialism close to the Brandomianone. At that time, Wittgenstein suggests that every sentence should beinferentially thick, that is, logically connected to several others. To explainthe nature of the negation related to material incompatibilities presented in the collapse of Wittgenstein’s version of logical atomism the paper also investigatesBrandom’s use of the distinction between contrariety and contradiction.