In principle, the Phenomenological Fundamental Consideration contains the solution of all epistemological dilemmas that cannot be resolved in the natural attitude. If a phenomenology remains partly stuck in this natural attitude, as did the philosophy of LU, it cannot reach clarity in these matters. It then remains on the level of a psychology of reason unable to overcome the problematics of the thing in itself without falling prey to psychologism. In this chapter, I will show that Husserl, through the new transcendental turn, is able to produce the desired critique of reason that he struggled to formulate in his publications from LU on. His long struggle to achieve clarity in this area finally resulted in a principial solution in the form of a transcendental phenomenological idealism. As I see it, Husserl's thinking at this stage is definitive, despite the later modifications.