Propositional attitudes like knowledge, belief, and assertion play an important foundational role for semantic theory, the goal of which is to specify the meanings of sentences and their semantic contents relative to contexts of utterance. Meanings are plausibly regarded as functions from such contexts to semantic contents, which in turn are closely related to the assertions made, and the beliefs expressed, by utterances. For example, the semantic content of I live in New Jersey in a context C with x as agent and t as time is standardly taken to be the proposition that x lives in New Jersey at t. To understand the meaning of this sentence is, to a first approximation, to know that a competent speaker x who sincerely and assertively utters it in C asserts, and expresses a belief in, this proposition. Roughly put, if p...