Simply from the idea of moral perfection, which reason frames a priori and connects inseparably with the notion of a free will. Imitation finds no place at all in morality, and examples serve only for encouragement, i.e., they put beyond doubt the feasibility of what the law commands, they make visible that which the practical rule expresses more generally, but they can never authorize us to set aside the true original which lies in reason and to guide ourselves by examples.
If then there is no genuine supreme principle of morality but what must rest simply on pure reason, independent of all experience, Ithink it is not necessary even to put the question whether it is good to exhibit these concepts in their generality (in abstracto) as they are established a priori along with the principles belonging to them, if our knowledge is to be distinguished from the vulgar and to be called philosophical.
In our times indeed this might perhaps be necessary; for if we collected votes whether pure rational knowledge separated from everything empirical, that is to say, metaphysic of morals, or whether popular practical philosophy is to be preferred, it is easy to guess which side would preponderate.
This descending to popular notions is certainly very commendable, if the ascent to the principles of pure reason has first taken place and been satisfactorily accomplished. This implies that we first found ethics on metaphysics, and then, when it is firmly established, procure a hearing for it by giving it a popular character. But it is quite absurd to try to be popular in the first inquiry, on which the soundness of the principles depends. It is not only that this proceeding can never lay claim to the very rare merit of a true philosophical popularity, since there is no art in being intelligible if one renounces all thoroughness of insight; but also it produces a disgusting medley of compiled observations and half-reasoned principles. Shallow pates enjoy this because it can be used for every-day chat, but the sagacious find in it only confusion, and being unsatisfied and unable to help themselves, they turn away their eyes, while philosophers, who see quite well through this delusion, are little listened to when they call men off for a time from this pretended popularity, in order that they might be rightfully popular after they have attained a definite insight.
We need only look at the attempts of moralists in that favourite fashion, and we shall find at one time the special constitution of human nature (including, however, the idea of a rational nature generally), at one time perfection, at another happiness, here moral sense, there fear of God. a little of this, and a little of that, in marvellous mixture, without its occurring to them to ask whether the principles of morality are to be sought in the knowledge of human nature at all (which we can have only from experience); or, if this is not so, if these principles are to be found altogether a priori, free from everything empirical, in pure rational concepts only and nowhere else, not even in the smallest degree; then rather to adopt the method of making this a separate inquiry, as pure practical philosophy, or (if one may use a name so decried) as metaphysic of morals,* to bring it by itself to completeness, and to require the public, which wishes for popular treatment, to await the issue of this undertaking.
*Just as pure mathematics are distinguished from applied, pure logic from applied, so if we choose we may also distinguish pure philosophy of morals (metaphysic) from applied (viz., applied to human nature). By this designation we are also at once reminded that moral principles are not based on properties of human nature, but must subsist a priori of themselves, while from such principles practical rules must be capable of being deduced for every rational nature, and accordingly for that of man.
Such a metaphysic of morals, completely isolated, not mixed with any anthropology, theology, physics, or hyperphysics, and still less with occult qualities (which we might call hypophysical), is not only an indispensable substratum of all sound theoretical knowledge of duties, but is at the same time a desideratum of the highest importance to the actual fulfilment of their precepts. For the pure conception of duty, unmixed with any foreign addition of empirical attractions, and, in a word, the conception of the moral law, exercises on the human heart, by way of reason alone (which first becomes aware with this that it can of itself be practical), an influence so much more powerful than all other springs* which may be derived from the field of experience, that, in the consciousness of its worth, it despises the latter, and can by degrees become their master; whereas a mixed ethics, compounded partly of motives drawn from feelings and inclinations, and partly also of conceptions of reason, must make the mind waver between motives which cannot be brought under any principle, which lead to good only by mere accident and very often also to evil.
