Kant claimed that human beings' representation of the world depends on a system of fundamental categories or “pure concepts of the understanding.” He also claimed that these categories were originally nothing other than elementary logical functions, which find expression in logical forms of judgment. Kant expounded these functions in a systematic “table” which then became the architectonic principle not only for the Critique of Pure Reason, but also for the Critique of Practical Reason and the Critique of Judgment. In a famous footnote to the Metaphysical Foundations of Natural Science, Kant claimed that as long as one accepted the two cornerstones of his doctrine – the merely sensible, receptive character of our intuitions, for which space and time are a priori forms and the derivation of categories from logical functions of judgment – then it mattered little if the details of his proofs (in particular, the details of his transcendental deduction of the categories) failed to carry complete conviction in the eyes of his readers. For the two main points of his demonstration, as far as he was concerned, were sufficiently established. Those two points are that (1) we have a priori concepts of objects originating in the understanding alone; and (2) these concepts can be applied in cognition only to appearances (that is, to objects given in accordance with the a priori forms of space and time), not to things as they are in themselves.