Some thirty-eight years after publication of the Philosophy of Arithmetic,¹ Husserl wrote the following appraisal of it: "Thus it was, expressed in my later way of speaking, a phenomenological-constitutional study. It was also the first that attempted to make "categorical objectivities' ... understandable out of constituting intentional activity ...." ² In other places of his work, Husserl criticizes his Philosophy of Arithmetic because it was tainted with psychologism, but the judgment expressed in Formal and Transcendental Logic shows that he never repudiated his first work completely; rather, as regards the concept of constitution, he considered it quite in keeping with the type of investigation he was to develop in the years to follow.³ But to what does Husserl refer, when he says that the Philosophy of Arithmetic contains explanations of constitution?