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I must leave it to those who are acquainted with works of this kind to judge whether such a system as that of the practical reason, which is here developed from the critical examination of it, has cost much or little trouble, especially in seeking not to miss the true point of view from which the whole can be rightly sketched. It presupposes, indeed, the Fundamental Principles of the Metaphysic of Morals, but only in so far as this gives a preliminary acquaintance with the principle of duty, and assigns and justifies a definite formula thereof; in other respects it is independent. * It results from the nature of this practical faculty itself that the complete classification of all practical sciences cannot be added, as in the critique of the speculative reason. For it is not possible to define duties specially, as human duties, with a view to their classification, until the subject of this definition (viz., man) is known according to his actual nature, at least so far as is necessary with respect to duty; this, however, does not belong to a critical examination of the practical reason, the business of which is only to assign in a complete manner the principles of its possibility, extent, and limits, without special reference to human nature. The classification then belongs to the system of science, not to the system of criticism.

PREFACE ^paragraph 15

     * A reviewer who wanted to find some fault with this work
     has hit the truth better, perhaps, than he thought, when he
     says that no new principle of morality is set forth in it,
     but only a new formula. But who would think of introducing a
     new principle of all morality and making himself as it were
     the first discoverer of it, just as if all the world before
     him were ignorant what duty was or had been in thorough-
     going error? But whoever knows of what importance to a
     mathematician a formula is, which defines accurately what is
     to be done to work a problem, will not think that a formula
     is insignificant and useless which does the same for all
     duty in general.

In the second part of the Analytic I have given, as I trust, a sufficient answer to the objection of a truth-loving and acute critic * of the Fundamental Principles of the Metaphysic of Morals- a critic always worthy of respect- the objection, namely, that the notion of good was not established before the moral principle, as he thinks it ought to have been. ** I have also had regard to many of the objections which have reached me from men who show that they have at heart the discovery of the truth, and I shall continue to do so (for those who have only their old system before their eyes, and who have already settled what is to be approved or disapproved, do not desire any explanation which might stand in the way of their own private opinion.)

PREFACE ^paragraph 20

     * [See Kant's "Das mag in der Theoric ricktig seyn," etc.
     Werke, vol. vii, p. 182.]

     ** It might also have been objected to me that I have not
     first defined the notion of the faculty of desire, or of the
     feeling of Pleasure, although this reproach would be unfair,
     because this definition might reasonably be presupposed as
     given in psychology. However, the definition there given
     might be such as to found the determination of the faculty
     of desire on the feeling of pleasure (as is commonly done),
     and thus the supreme principle of practical philosophy would
     be necessarily made empirical, which, however, remains to be
     proved and in this critique is altogether refuted. It will,
     therefore, give this definition here in such a manner as it
     ought to be given, in order to leave this contested point
     open at the beginning, as it should be. LIFE is the faculty
     a being has of acting according to laws of the faculty of
     desire. The faculty of DESIRE is the being's faculty of
     becoming by means of its ideas the cause of the actual
     existence of the objects of these ideas. PLEASURE is the
     idea of the agreement of the object, or the action with the
     subjective conditions of life, i.e., with the faculty of
     causality of an idea in respect of the actuality of its
     object (or with the determination of the forces of the
     subject to action which produces it). I have no further need
     for the purposes of this critique of notions borrowed from
     psychology; the critique itself supplies the rest. It is
     easily seen that the question whether the faculty of desire
     is always based on pleasure, or whether under certain
     conditions pleasure only follows the determination of
     desire, is by this definition left undecided, for it is
     composed only of terms belonging to the pure understanding,
     i.e., of categories which contain nothing empirical. Such
     precaution is very desirable in all philosophy and yet is
     often neglected; namely, not to prejudge questions by
     adventuring definitions before the notion has been
     completely analysed, which is often very late. It may be
     observed through the whole course of the critical philosophy
     (of the theoretical as well as the practical reason) that
     frequent opportunity offers of supplying defects in the old
     dogmatic method of philosophy, and of correcting errors
     which are not observed until we make such rational use of
     these notions viewing them as a whole.

When we have to study a particular faculty of the human mind in its sources, its content, and its limits; then from the nature of human knowledge we must begin with its parts, with an accurate and complete exposition of them; complete, namely, so far as is possible in the present state of our knowledge of its elements. But there is another thing to be attended to which is of a more philosophical and architectonic character, namely, to grasp correctly the idea of the whole, and from thence to get a view of all those parts as mutually related by the aid of pure reason, and by means of their derivation from the concept of the whole. This is only possible through the most intimate acquaintance with the system; and those who find the first inquiry too troublesome, and do not think it worth their while to attain such an acquaintance, cannot reach the second stage, namely, the general view, which is a synthetical return to that which had previously been given analytically. It is no wonder then if they find inconsistencies everywhere, although the gaps which these indicate are not in the system itself, but in their own incoherent train of thought.

I have no fear, as regards this treatise, of the reproach that I wish to introduce a new language, since the sort of knowledge here in question has itself somewhat of an everyday character. Nor even in the case of the former critique could this reproach occur to anyone who had thought it through and not merely turned over the leaves. To invent new words where the language has no lack of expressions for given notions is a childish effort to distinguish oneself from the crowd, if not by new and true thoughts, yet by new patches on the old garment. If, therefore, the readers of that work know any more familiar expressions which are as suitable to the thought as those seem to me to be, or if they think they can show the futility of these thoughts themselves and hence that of the expression, they would, in the first case, very much oblige me, for I only desire to be understood: and, in the second case, they would deserve well of philosophy. But, as long as these thoughts stand, I very much doubt that suitable and yet more common expressions for them can be found. *