Kaplan's Puzzle, Dynamic Senses, and Diachronically Individuated Propositions

Abstract

The Fregean encounters a few interconnected problems in its account of indexical sentences, each posed in one way or another by Kaplan's puzzle of cognitive dynamics. For one, there's a problem defending the doctrine that the very same propositions can be expressed in relevantly different contexts. And two, there's the problem of cases where the same indexically expressed belief, the content of which is a Fregean proposition, seems to be retained by a subject yet the subject is unable to express her belief with the correct indexical due to contextual mislocation. Both are related to the puzzle of cognitive dynamics, but for the Fregean appear in the form of what I'll call The Re-expressibility Problem--since the more fundamental Fregean principle of propositional re-expressibility is being undermined. Consideration of other Fregean commitments shows that the only way to adjudicate the problem is by demonstrating that different coreferring indexicals can have the same sense. After demonstrating that different coreferring indexicals can have the same sense, it is then shown that these indexical senses must be dynamic entities, persisting through changes of context. The puzzle of cognitive dynamics reappears as something of an objection to the proposed solution to the The Re-expressibility Problem. The final portion of the paper is devoted to answering these objections and dispelling the puzzlement engendered by Kaplan's `cognitive dynamics'.