 One main reason why neo-Kantians of all stripes see the essence of philosophy in critique is that it guarantees philosophy’s autonomy (cf. Natorp 1887: 266–269, 285, et passim). Of all rational activities, philosophy alone has the task of discovering the conditions and regulative ideals that make such activities at all possible. While the problem of philosophy’s identity as a discipline of course goes back to Plato, we are faced, in the nineteenth-century German context, with the particular problem of philosophy’s relation to the positive sciences, which had completely repudiated and replaced the knowledge-claims of the speculative systems of German Idealism. For the Marburgers, the issue of philosophy’s disciplinary integrity becomes intertwined with the question of the autonomy of reason itself. Cohen and Natorp faced a difficult task. Having turned their backs on speculative philosophy, they could not define reason’s autonomy by falling back upon the discredited Geist of German  Idealism.[7]  But they also could not let reason (or as they prefer to call it, “thinking”) be conceived as a set of psychological operations, since that would subject reason’s laws (logic) to more basic psychological or psychophysical laws. Already in his (1887), Natorp objects to such psychologism (though he does not use the term) on the grounds that science and knowledge, and the very notion of objective truth these presuppose, would be rendered senseless if grounded in the subjective experience of the thinking or knowing psyche (see esp.  Section 4).  The chief task for any account of Natorp’s philosophy, then, is to make sense of his notion of rational autonomy.