 The second idea—the primacy of the sentential—has its roots in the thought that the fundamental uses of a term are in assertion and argument: if we understand the use of a defined term in assertion and argument then we fully grasp the term. The sentential is, however, primary in argument and assertion. Hence, to explain the use of a defined term \(X\), the second idea maintains, it is necessary and sufficient to explain the use of sentential items that contain \(X\). (Sentential items are here understood to include sentences and sentence-like things with free variables, e.g., the definiens of (4); henceforth, these items will be called formulas.) The issues the second idea raises are, of course, large and important, but they cannot be addressed in a brief survey. Let us accept the idea simply as a given.