ABSTRACT
The propositional theory postulates text bases of certain kinds, and one can experimentally investigate their properties, even though the rules that relate text and base are not explicitly available. A text base must contain information about whether a noun phrase is used as a definite or indefinite term. Several proposals for a semantic base distinguish two separate sentence constituents: modality and propositions. Among the many possible relations among propositions, implication and presupposition have received special attention in recent years. English sentences are always tensed statements, but the propositions that constitute a text base, and from which the sentences are supposedly derived, are not. Lexical entries for quantifiers must contain statements about how the term is to be used, and what its implications are. Inferences about temporal relationships must be possible within a semantic system. Precise temporal information must be available in the subjective lexicon, and the information must be in such a format that it can be readily processed.
