The solution of the problems of pure geometry does not belong to a particular part of the science; mensuration does not deserve the name of practical, in contrast to pure, geometry, as a second part of geometry in general; and just as little ought the mechanical or chemical art of experiment or observation to be reckoned as a practical part of the doctrine of Nature. Just as little, in fine, ought housekeeping, farming, statesmanship, the art of conversation, the prescribing of diet, the universal doctrine of happiness itself, or the curbing of the inclinations and checking of the affections for the sake of happiness, to be reckoned as practical Philosophy, or taken to constitute the second part of Philosophy in general. For all these contain only rules of skill (and are consequently only technically practical) for bringing about an effect that is possible according to the natural concepts of causes and effects, which, since they belong to theoretical Philosophy, are subject to those precepts as mere corollaries from it (viz. natural science), and can therefore claim no place in a special Philosophy called practical. On the other hand, the morally practical precepts, which are altogether based on the concept of freedom to the complete exclusion of the natural determining grounds of the will, constitute a quite special class. These, like the rules which nature obeys, are called simply laws, but they do not, like them, rest on sensuous conditions but on a supersensible principle; and accordingly they require for themselves a quite different part of Philosophy, called practical, corresponding to its theoretical part. We hence see that a complex of practical precepts given by Philosophy does not constitute a distinct part of Philosophy, as opposed to the theoretical part, because these precepts are practical; for they might be that, even if their principles were derived altogether from the theoretical cognition of nature (as technically practical rules). [A distinct branch of Philosophy is constituted only] if their principle, as it is not borrowed from the natural concept, which is always sensuously conditioned, rests on the supersensible, which alone makes the concept of freedom cognisable by formal laws. These precepts are then morally practical, _i.e._ not merely precepts or rules in this or that aspect, but, without any preceding reference to purposes and designs, are laws. II. OF THE REALM OF PHILOSOPHY IN GENERAL So far as our concepts have _a priori_ application, so far extends the use of our cognitive faculty according to principles, and with it Philosophy. But the complex of all objects, to which those concepts are referred, in order to bring about a knowledge of them where it is possible, may be subdivided according to the adequacy or inadequacy of our [cognitive] faculty to this design.