The Critique of Judgement

We may call the faculty of cognition from principles a priori, pure Reason, and the inquiry into its possibility and bounds generally the Critique of pure Reason, although by this faculty we only understand Reason in its theoretical employment, as it appears under that name in the former work; without wishing to inquire into its faculty, as practical Reason, according to its special principles. That [Critique] goes merely into our faculty of knowing things a priori, and busies itself therefore only with the cognitive faculty to the exclusion of the feeling of pleasure and pain and the faculty of desire; and of the cognitive faculties it only concerns itself with Understanding, according to its principles a priori, to the exclusion of Judgement and Reason (as faculties alike belonging to theoretical cognition), because it is found in the sequel that no other cognitive faculty but the Understanding can furnish constitutive principles of cognition a priori. The Critique, then, which sifts them all, as regards the share which each of the other faculties might pretend to have in the clear possession of knowledge from its own peculiar root, leaves nothing but what the Understanding prescribes a priori as law for nature as the complex of phenomena (whose form also is given a priori). It relegates all other pure concepts under Ideas, which are transcendent for our theoretical faculty of cognition, but are not therefore useless or to be dispensed with. For they serve as regulative principles; partly to check the dangerous pretensions of Understanding, as if (because it can furnish a priori the conditions of the possibility of all things which it can know) it had thereby confined within these bounds the possibility of all things in general; and partly to lead it to the consideration of nature according to a principle of completeness, although it can never attain to this, and thus to further the final design of all knowledge.