The Semantics of Terms. Signification and Extension
This chapter explores semantics in Charles W. Morris’ sense of the term: the study of the relation of words to things. Two concepts prove to be fundamental to the Logic’s semantics: signification and extension. The chapter sets out the semantics of terms, both substantives and adjectives, and the special semantics of species. Extension is one of the more important concepts in the Logic’s metatheory because it plays a central role in the statement of truth-conditions. On the surface, extension has a rather simple definition: an idea’s extension is the collection of its inferior ideas. The mechanism of signification varies depending on an idea’s grammatical type. Ontologically, terms and propositions are mental acts, which are modes of the soul. The technical fact that there is a one-to-one correspondence between extensions and significance ranges ensures that truth can be defined in terms of relations among extensions, which are sets of ideas, yet nevertheless be about things in the world.