In Defence of Logical Omniscience

Abstract

The most controversial consequence of Robert Stalnaker’s (1984) theory of propositional attitudes is that subjects of propositional attitudes are logically omniscient. What makes this consequence problematic is that it seems to conflict with the fact that subjects of propositional attitudes are also deductive reasoners. Stalnaker’s solution to this problem consists in two complementary theories. According to the metalinguistic theory, deductive information is metalinguistic, and according to the integration theory, deductive reasoning proceeds via integration of dispositions to act. In my thesis I will defend Stalnaker’s solution against two arguments, namely the translation argument (Moore 1995, Nuffer 2009) and the argument from logical oversight (Moore 1995, Jago 2014). In my responses I will rely on a Tractarian distinction between signs and symbols, showing that it brings out a similar flaw in both arguments. The flaw in the first is the assumption that the same sentence cannot be written in two different languages, and the flaw in the second is the assumption that two different logical connectives cannot be written in the same way. In my response to the first of these arguments, I will also develop a variation of Stalnaker’s metalinguistic theory that accounts for the sign/symbol distinction.