CARNAP'S CONVENTIONALISM: THE PROBLEM WITH P-RULES

Rudolf Carnap's 'Principle of Tolerance' was undoubtedly one of the most influential precepts in 20th Century philosophy. Introduced in The Logical Syntax of Language, Carnap's Principle suffered from ambiguities which aroused important philosophical questions from Moritz Schlick (in 1935) and Alberto Coffa (1991). Specifically, their questions arise from the application of the Principle to the matter of including extra-logical transformation rules (so-called 'physical rules' or 'P-rules') in the definition of a language, which Carnap regarded as an important difference between his own conventionalist philosophy of logic and the 'absolutist' conception of Wittgenstein's Tractatus. Yet both Schlick and Coffa suggested that applying the Tolerance precept to this matter exceeds the limits of its legitimate deployment. Upon considering their objections, as well as the criticism of Wittgenstein which evoked them, it is argued that the philosophical significance of the Principle of Tolerance requires its strict limitation to matters pertaining to the determination of meaning.