In his later polemical work against Eberhard, Kant uses the concept of “original acquisition” to defend the critical meaning of his own concept of the “a priori”. It is well known that the former has been borrowed from the modern idea of natural law. In this paper, I try to clarify how the former characterizes the latter in Kant's critical epistemology, referring to a certain Kantian transformation of the traditional concept of “innate”. Drawing on the dualism of human cognitive faculties, (...) i.e. of sensibility and understanding, the conception of “original acquisition” can distinguish the apriority of the transcendental imagination from the rest of the a priori apparatus. Thus the concept of “original acquisition” points to one of the central theses in the first Critique. (shrink)