 Throughout most of his semantic work, Montague avowedly adopted a version of Frege’s (1892) distinction between ‘sense’ and ‘denotation’. Frege’s original line of thought concerns sentences like The Greeks did not know that the morning star is the evening star, which does not seem to express that the Greeks were confused about the self-identity of Venus. Frege’s analysis accounts for this observation by having descriptive names like the morning star denote their referents in ordinary contexts, but something different in embedded clauses (or, more generally, in ‘indirect contexts’): their ‘sense’ – a semantic value that captures the way in which an object is referred to. Since referring to a celestial object by the morning star differs from referring to it by the evening star, the embedded clause does not denote an analytic truth but a contingent proposition, whose truth may well have escaped the Greeks.