of taste (for this will take its course in the future as in the past without any such investigations), but merely in a transcendental point of view. Hence, I trust that as regards the deficiency of the former purpose it will be judged with indulgence, though in the latter point of view it must be prepared for the severest scrutiny. But I hope that the great difficulty of solving a problem so involved by nature may serve as excuse for some hardly avoidable obscurity in its solution, if only it be clearly established that the principle is correctly stated. I grant that the mode of deriving the phenomena of the Judgement from it has not all the clearness which might be rightly demanded elsewhere, viz. in the case of cognition according to concepts; but I believe that I have attained to it in the second part of this work.
Here then I end my whole critical undertaking. I shall proceed without delay to the doctrinal [part] in order to profit, as far as is possible, by the more favourable moments of my increasing years. It is obvious that in this [part] there will be no special section for the Judgement, because in respect of this faculty Criticism serves instead of Theory; but, according to the division of Philosophy (and also of pure Philosophy) into theoretical and practical, the Metaphysic of Nature and of Morals will complete the undertaking.
INTRODUCTION
I. OF THE DIVISION OF PHILOSOPHY
We proceed quite correctly if, as usual, we divide Philosophy, as containing the principles of the rational cognition of things by means of concepts (not merely, as logic does, principles of the form of thought in general without distinction of Objects), into theoretical and practical. But then the concepts, which furnish their Object to the principles of this rational cognition, must be specifically distinct; otherwise they would not justify a division, which always presupposes a contrast between the principles of the rational cognition belonging to the different parts of a science.
Now there are only two kinds of concepts, and these admit as many distinct principles of the possibility of their objects, viz. natural concepts and the concept of freedom. The former render possible theoretical cognition according to principles a priori; the latter in respect of this theoretical cognition only supplies in itself a negative principle (that of mere contrast), but on the other hand it furnishes fundamental propositions which extend the sphere of the determination of the will and are therefore called practical. Thus Philosophy is correctly divided into two parts, quite distinct in their principles; the theoretical part or Natural Philosophy, and the practical part or Moral Philosophy (for that is the name given to the practical legislation of Reason in accordance with the concept of freedom). But up to the present a gross misuse of these expressions has prevailed, both in the division of the different principles and consequently also of Philosophy itself. For what is practical according to natural concepts has been identified with the practical according to the concept of freedom; and so with the like titles, ‘theoretical’ and ‘practical’ Philosophy, a division has been made, by which in fact nothing has been divided (for both parts might in such case have principles of the same kind).
The will, regarded as the faculty of desire, is (in this view) one of the many natural causes in the world, viz. that cause which acts in accordance with concepts. All that is represented as possible (or necessary) by means of a will is called practically possible (or necessary); as distinguished from the physical possibility or necessity of an effect, whose cause is not determined to causality by concepts (but in lifeless matter by mechanism and in animals by instinct). Here, in respect of the practical, it is left undetermined whether the concept which gives the rule to the causality of the will, is a natural concept or a concept of freedom.
But the last distinction is essential. For if the concept which determines the causality is a natural concept, then the principles are technically practical; whereas, if it is a concept of freedom they are morally practical. And as the division of a rational science depends on the distinction between objects whose cognition needs distinct principles, the former will belong to theoretical Philosophy (doctrine of Nature), but the latter alone will constitute the second part, viz. practical Philosophy (doctrine of Morals).
All technically practical rules (i.e. the rules of art and skill generally, or of prudence regarded as skill in exercising an influence over men and their wills), so far as their principles rest on concepts, must be reckoned only as corollaries to theoretical Philosophy. For they concern only the possibility of things according to natural concepts, to which belong not only the means which are to be met with in nature, but also the will itself (as a faculty of desire and consequently a natural faculty), so far as it can be determined conformably to these rules by natural motives. However, practical rules of this kind are not called laws (like physical laws), but only precepts; because the will does not stand merely under the natural concept, but also under the concept of freedom, in relation to which its principles are called laws. These with their consequences alone constitute the second or practical part of Philosophy.
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
