Applied Logic without Psychologism

摘要

Logic is a celebrated representation language because of its formal generality.But there are two senses in which a logic may be considered general, one that concernsa technical ability to discriminate between different types of individuals, and anotherthat concerns constitutive norms for reasoning as such. This essay embraces the former,permutation-invariance conception of logic and rejects the latter, Fregean conception oflogic. The question of how to apply logic under this pure invariantist view is addressed, anda methodology is given. The pure invariantist view is contrasted with logical pluralism,and a methodology for applied logic is demonstrated in remarks on a variety of issuesconcerning non-monotonic logic and non-monotonic inference, including Charles Morgan'simpossibility results for non-monotonic logic, David Makinson's normative constraints fornon-monotonic inference, and Igor Douven and Timothy Williamson's proposed formalconstraints on rational acceptance.