The paper aims at a clarification of Frege’s antipsychologism. It analyses Frege’s putting into opposition of logic/mathematics and psychology. It then investigates the historical roots of Frege’s views in Kant’s Critique of Pure Reason and in J. Müller’s and H. von Helmholtz’s physiological psychology. It explicates also how the opposition between Frege’s (third) realm of thoughts and that of representations is rooted in the opposition of a transcendentally understood subject (consciousness) and a naturalistic understanding of an empirical subject (consciousness), as well as its implications in the philosophy of logical positivism/empiricism. Finally, by drawing on Habermas’ linguistico-pragmatically grounded understanding of the lifeworld it shows how that opposition can be overcome and how to understand Frege’s realm of thoughts.