It is still a widely used cliché to simply characterize Kant's a priori as innate or to put it on a level with the traditional doctrine of innate ideas. But the all too simple consideration that representations, which are the precondition for experience, must have existed before any experience and thus be innate, does not do justice to Kant's ideas about the origin of a priori representations. Kant himself was a decided opponent of the doctrine of innate ideas, and in many places in his works he explicitly said again and again that the forms of intuition, space and time, as well as the pure concepts, are acquired, however not from experience, but rather from the very nature of cognitive faculty. This investigation aims at a complete presentation of this theory of an »original acquisition« of knowledge, which has so far been inexcusably neglected by research. It will be shown that the theory, never fully elaborated and only presented in hints and fragments by Kant, regarding development as well as systematic stands in the centre of critical philosophy. It was the theory of the origin of certain representations in the cognitive faculty itself, formulated already in the dissertation of 1770 and thus in the context of an entirely different idea of metaphysics that confronted Kant with the question of how such concepts can refer to objects at all. With respect to the development of Kant's way of thinking the theory of original acquisition of a priori concepts is the basis of the so-called problem of deduction, and is the key to Kant's epistemological change of 1772. According to Kant's theory of acquisition the a priori concepts arise from the logical rules of thought, from which they develop when these rules are applied to objects of the senses. He said this as early as 1770. As the logical rules are all well-known, they provide Kant with the »Leitfaden«, the clue, that enables him to define the a priori concepts completely, Kant derives the categories from the forms of judgments and the ideas from the forms of syllogism in the Critique of Pure Reason, on the basis of his theory of acquisition. He derives the transcendental faculty of pure concepts from the logical faculty of judgment and inferring, respectively, because the logical faculty is the origin of the transcendental one. In a systematic respect Kant's acquisition theory of knowledge is thus a key to the central question for the relationship of formal and transcendental logic and the reason of the basic structure of the Critique of Pure Reason.