Tense, Modality, and Semantic Values

Here is a rough sketch of what I take to be an attractive, albeit naı̈ve, picture (its attractiveness I take to be obvious; its naiveté, though perhaps also obvious, will be discussed shortly). A primary purpose of a semantics for a natural language is to compositionally assign to sentences semantic values that determine whether the sentences are true or false. Since natural languages contain contextually sensitive expressions, semantic values must be assigned to sentences relative to contexts. These semantic values are propositions. Sentence types may also be associated with higher level semantic values that are or determine functions from contexts to propositions (something like what David Kaplan calls ‘‘character’’). Propositions are the primary bearers of truth and falsity. Propositions are also the objects of our attitudes: they are things we doubt, believe, and think. Further, sentences that contain verbs of propositional attitude, such as