 The notion of an indirect interpretation was introduced by Carnap in his Foundations of Logic and Mathematics (1939: ch. 23–24) with the intention of accounting for the semantics of theoretical terms in physics. It goes without saying that this notion is understood against the background of the notion of a direct interpretation. Carnap had the following distinction in mind. The interpretation of a descriptive symbol is direct if and only if (i) it is given by an assignment of an extension or an intension, and (ii) this assignment is made by expressions of the metalanguage. The interpretation of a descriptive symbol is indirect, by contrast, if and only if it is specified by one or several sentences of the object language, which then figure as axioms in the respective calculus. Here are two simple examples of a direct interpretation: