 Quine (1943) and Church (1951) rehabilitated Frege’s distinction of sense and reference. Non-designating words such as ‘Pegasus’ cannot be meaningless: it is precisely the meaning of ‘Pegasus’ that allows speakers to establish that the word lacks reference. Moreover, as Frege (1892) had argued, true factual identities such as “Morning Star = Evening Star” do not state synonymies; if they did, any competent speaker of the language would be aware of their truth. Along these lines, Carnap (1947) proposed a new formulation of the sense/reference dichotomy, which was translated into the distinction between intension and extension. The notion of intension was intended to be an explicatum of Frege’s “obscure” notion of sense: two expressions have the same intension if and only if they have the same extension in every possible world or, in Carnap’s terminology, in every state description (i.e., in every maximal consistent set of atomic sentences and negations of atomic sentences). Thus, ‘round’ and ‘spherical’ have the same intension (i.e., they express the same function from possible worlds to extensions) because they apply to the same objects in every possible world. Carnap later suggested that intensions could be regarded as the content of lexical semantic competence: to know the meaning of a word is to know its intension, “the general conditions which an object must fulfill in order to be denoted by [that] word” (Carnap 1955). However, such general conditions were not spelled out by Carnap (1947). Consequently, his system did not account, any more than Tarski’s, for semantic differences and relations among words belonging to the same semantic category: there were possible worlds in which the same individual a could be both a married man and a bachelor, as no constraints were placed on either word’s intension. One consequence, as Quine (1951) pointed out, was that Carnap’s system, which was supposed to single out analytic truths as true in every possible world, “Bachelors are unmarried”—intuitively, a paradigmatic analytic truth—turned out to be synthetic rather than analytic.