Frege was particularly opposed to empiricism and psychologism, which, according to him, are connected with each other and lead in the long run to idealism. His own philosophical position as it emerges from his criticism of empiricism and psychologism can be described as an epistemology devoted to maintaining the objectivity of knowledge founded on the human capacity for grasping thoughts, a capacity manifested by our use of language. The very centre of his philosophy is a systematic theory that explores the connections between thought, truth and judgements and aims at establishing a basic notion of knowledge.

The epistemological significance of this theory can be shown in at least three ways. First, Frege makes use of his theory to criticise various epistemological views. In his opposition to empiricism, he objects that what is real does not coincide with what is objective; only his own theory, he claims, provides a proper place for the domain of thought. Idealism and scepticism are discussed and evaluated within the framework of the theory of reference. Second, fundamental notions of Frege's philosophy, such as the idea of the cognitive value of a sentence and his conception of judgement, are epistemological notions. Finally, the development of his philosophical thought tends clearly to culminate in an outright epistemological theory about the “sources of knowledge”. His final full-blown position does not represent a completely new turn in his philosophy but is, as always in Frege, a refinement and elaboration of his earlier views and can be traced back to the very beginning of his philosophy.