 In the opening paragraph of “On Sense and Reference” (Frege 1892), Frege argues that a theory that identifies the semantic value of a name with its referent—the naïve theory—cannot differentiate between the contents of ‘Hesperus = Hesperus’ and ‘Hesperus = Phosphorus’. Given the plausible assumption that the proposition expressed by a sentence is a function of the semantic values of its constituent expressions together with their mode of combination, it seems inevitable that what the latter sentence says is just what the former sentence says—assuming, with the naïve theory, that ‘Hesperus’ and ‘Phosphorus’ possess the same semantic value. Of course, the latter sentence is potentially informative, whereas the former sentence is not. This leads Frege to reject the naïve theory. He also rejects, for reasons that need not detain us, a view according to which identity is a relation between the names ‘Hesperus’ and ‘Phosphorus’. The view he settles on is that the contribution that ‘Hesperus’ makes to the propositions expressed by the above-quoted identity sentences is a sense —a way of thinking of the referent. (While one might say that the semantic value of ‘Hesperus’ is the associated sense, this would be incorrect, since, on Frege’s view, ‘Hesperus’ has two semantic values—its sense, and the referent determined by this sense. The proposition expressed by, e.g., ‘Hesperus = Phosphorus’ is partly determined by this sense, whereas the referent of this sentence—for Frege, its truth-value—is partly determined by the associated referent.)