It is not in the least more difficult to conceive how the laws of the phenomena of nature must harmonize with the understanding and with its a priori form- that is, its faculty of conjoining the manifold-than it is to understand how the phenomena themselves must correspond with the a priori form of our sensuous intuition.For laws do not exist in the phenomena any more than the phenomena exist as things in themselves.Laws do not exist except by relation to the subject in which the phenomena inhere, in so far as it possesses understanding, just as phenomena have no existence except by relation to the same existing subject in so far as it has senses.To things as things in themselves, conformability to law must necessarily belong independently of an understanding to cognize them.But phenomena are only representations of things which are utterly unknown in respect to what they are in themselves.But as mere representations, they stand under no law of conjunction except that which the conjoining faculty prescribes.Now that which conjoins the manifold of sensuous intuition is imagination, a mental act to which understanding contributes unity of intellectual synthesis, and sensibility, manifoldness of apprehension.Now as all possible perception depends on the synthesis of apprehension, and this empirical synthesis itself on the transcendental, consequently on the categories, it is evident that all possible perceptions, and therefore everything that can attain to empirical consciousness, that is, all phenomena of nature, must, as regards their conjunction, be subject to the categories.And nature (considered merely as nature in general) is dependent on them.as the original ground of her necessary conformability to law (as natura formaliter spectata).But the pure faculty (of the understanding) of prescribing laws a priori to phenomena by means of mere categories, is not competent to enounce other or more laws than those on which a nature in general, as a conformability to law of phenomena of space and time, depends.Particular laws, inasmuch as they concern empirically determined phenomena, cannot be entirely deduced from pure laws, although they all stand under them.Experience must be superadded in order to know these particular laws; but in regard to experience in general, and everything that can be cognized as an object thereof, these a priori laws are our only rule and guide.
Result of this Deduction of the Conceptions of the Understanding.SS 23We cannot think any object except by means of the categories; we cannot cognize any thought except by means of intuitions corresponding to these conceptions.Now all our intuitions are sensuous, and our cognition, in so far as the object of it is given, is empirical.But empirical cognition is experience; consequently no a priori cognition is possible for us, except of objects of possible experience.**Lest my readers should stumble at this assertion, and the conclusions that may be too rashly drawn from it, I must remind them that the categories in the act of thought are by no means limited by the conditions of our sensuous intuition, but have an unbounded sphere of action.It is only the cognition of the object of thought, the determining of the object, which requires intuition.In the absence of intuition, our thought of an object may still have true and useful consequences in regard to the exercise of reason by the subject.But as this exercise of reason is not always directed on the determination of the object, in other words, on cognition thereof, but also on the determination of the subject and its volition, I do not intend to treat of it in this place.
But this cognition, which is limited to objects of experience, is not for that reason derived entirely, from, experience, but- and this is asserted of the pure intuitions and the pure conceptions of the understanding- there are, unquestionably, elements of cognition, which exist in the mind a priori.Now there are only two ways in which a necessary harmony of experience with the conceptions of its objects can be cogitated.Either experience makes these conceptions possible, or the conceptions make experience possible.The former of these statements will not bold good with respect to the categories (nor in regard to pure sensuous intuition), for they are a priori conceptions, and therefore independent of experience.The assertion of an empirical origin would attribute to them a sort of generatio aequivoca.Consequently, nothing remains but to adopt the second alternative (which presents us with a system, as it were, of the epigenesis of pure reason), namely, that on the part of the understanding the categories do contain the grounds of the possibility of all experience.But with respect to the questions how they make experience possible, and what are the principles of the possibility thereof with which they present us in their application to phenomena, the following section on the transcendental exercise of the faculty of judgement will inform the reader.