The theory of sense and reference brought about a major change in Frege's logical views. In “On Sense and Reference”, after having established that sentences may have a reference as well as a sense, he immediately gave a new account of judgement in terms of the theory. He mentioned several times that the theory had led him to a new conception of judgement. His account of identity sentences was also changed by the theory. At the very beginning of “On Sense and Reference”, Frege pointed out that any account of the cognitive value of such sentences had to apply the distinction of sense and reference to singular terms. We might wonder whether there is any connection between these two consequences of the theory. What has an account of the cognitive value of a particular class of sentences to do with a new explanation of the notion of judgement?

I shall try to show that a proper understanding of these consequences will pave the way for an epistemological interpretation of the theory of sense and reference. To show this I first consider what is new in Frege's new conception of judgement. I then show that this conception gives a satisfactory account of the relation of a thought to its truth value and provides the foundation of Frege's identification of judgement with knowledge that is, in turn, the basis for Frege's account of the cognitive value of sentences. Finally, I explore the epistemological significance of his theory of sense and reference.