Chapter 6 is dedicated to reconstructing how Kant sets limits to the validity of the categories. In my reading, the argument that establishes these limits belongs to the negative part of the critique of pure reason. I first find confirmation that it is correct to distinguish between a positive and a negative argument concerning the validity of the categories, the former belonging to transcendental philosophy and the latter to the critique of pure reason, in three different texts by Kant: the transcendental deduction of the categories, the Metaphysical Foundations of Natural Science and On the Use of Teleological Principles in Philosophy. However, since these texts provide different pictures concerning how the two arguments are related to one another, I analyze in which sense the negative argument depends on the positive one by reconstructing relevant passages in the B-deduction.