 The traditional account of definitions is founded on three ideas. The first idea is that definitions are generalized identities; the second, that the sentential is primary; and the third, that of reduction. The first idea—that definitions are generalized identities—motivates the traditional account’s inferential rules for definitions. These are, put crudely, that (i) any occurrence of the definiendum can be replaced by an occurrence of the definiens (Generalized Definiendum Elimination); and, conversely, (ii) any occurrence of the definiens can be replaced by an occurrence of the definiendum (Generalized Definiendum Introduction).