The most important anti-psychologistic thesis that Husserl wished to defend in the Prolegomena is that logic, as an a priori science, is not a real science but an ideal science. In this work he already observed that a proper conception of the distinction between these two kinds of sciences is only possible when the empiricist theory of abstraction is given up.¹ The question of abstraction is indeed the central problem in the founding of the ideal sciences. Therefore I will begin this chapter by taking up the new theory of abstraction. Then, in Chapters 4 and 5, I will deal with the question of the task of the philosophical analysis of origins in connection with the formal a priori sciences.