 According to Cohen, for Kant mathematical natural science is the starting-point of philosophical investigation. It is the explanandum that Kantian philosophy seeks to explain. It is then up to philosophy to identify and articulate the a priori laws in that experience that are responsible for making it objective. If it is less than obvious that this is Kant’s method in the Critique of Pure Reason, Cohen insists, it is at least clear in the Prolegomena. There, Kant is explicit that he begins by assuming that mathematical natural science provides us with genuine objective knowledge, and that it contains synthetic a priori principles; Kant is likewise explicit that his task is to identify the necessary conditions of those principles’ possibility, and that doing so will explain the objectivity of mathematical natural science. (Kant is also explicit that this method, which in the Prolegomena he calls the ‘analytic method,’ is not the method he uses in the Critique of Pure Reason, nor would it be suitable for the full project of the Critique. Cohen seems cheerfully undaunted by this textual anomaly.) (See Rendl 2018 for discussion of Cohen’s motivations for taking the analytic method of the Prolegomena as his guide.) 