(ていげんめいほう categorical imperative)
Now all imperatives command either hypothetically or categorically. The former represent the practical necessity of a possible action as means to something else that is willed (or at least which one might possibly will). The categorical imperative would be that which represented an action as necessary of itself without reference to another end, i.e., as objectively necessary.
There is therefore but one categorical imperative, namely, this: Act only on that maxim whereby thou canst at the same time will that it should become a universal law.
But what sort of law can that be, the conception of which must determine the will, even without paying any regard to the effect expected from it, in order that this will may be called good absolutely and without qualification? As I have deprived the will of every impulse which could arise to it from obedience to any law, there remains nothing but the universal conformity of its actions to law in general, which alone is to serve the will as a principle, i.e., I am never to act otherwise than so that I could also will that my maxim should become a universal law.
[A]ll rational beings come under the law that each of them must treat itself and all others never merely as means, but in every case at the same time as ends in themselves.
--from FUNDAMENTAL PRINCIPLES OF THE METAPHYSIC OF MORALS BY IMMANUEL KANT (Translated by Thomas Kingsmill Abbott)
`Act so as to treat rational and/or sensitive beings as ends and not merely as means.'
---D.D. Raphael
Kant's idea that you should always act so that the maxim of your action can become a universal law would exclude the sensible commuter's maxim: `always leave work after the rush hour is over'.
---Peter Singer
カントの用語。 ドイツ語ではkategorischer Imperativというそうだ。 無条件命法という訳語も見たことがある。 「(とにかく)〜せよ」という無条件な命令、またはその形式を指す。 「金が欲しかったら、あたしと結婚しなさいよ」 というような条件付きの命令である仮言命法と 対比して用いられる。
定言命法にはいくつかの定式があるが、代表的なのは 「あなたの格律(個人的なポリシー)は、 普遍的な法則になりうるもので、 またそうなってもあなたが後悔しないようなものでなければならない」 (上の引用参照)というもの。 この定式には(1)普遍化可能性のテストと(2)意欲可能性のテストが含まれている。
たとえば、あなたが「借金をしても、困ったときには返さない」 という格律が道徳的に正しいかどうかを確かめたいときは、 それをまず普遍化できるかどうかを考える。 カントによれば、みんながこの格律を採用すると、 だれも人を信用しなくなり、そもそもお金を貸すという慣習が存在しなくなる (ほんとかな?)。それゆえこの格律は普遍化できない。
また、「困った人がいても助けない」 という格律が道徳的に正しいかどうかを考えた場合、 カントの考えではこの格律は普遍化可能である。 すなわち、「自分のことは自分でなんとかしろ」 という格律は普遍化しても問題なくなりたつ。 しかし、 自分がほんとに困ったときにこのような法則があると きっと後悔するだろうから、意欲可能性のテストに合格せず、 やっぱりこれは道徳的ではないことになる、とカントは言う。
さらに詳しくは『道徳形而上学の基礎づけ』を参照のこと。
自律の項も参照せよ。
22/Oct/2000 追記; 01/June/2001更新
以下はカントによる命法についての説明。 人間は神と違い、理性の言うことには必ずしも従わない意志を持っている。 それゆえ、客観的な(正義の)法は、命法、 すなわち「なすべきこと」あるいは義務として人間の意志に提示される。 言いかえると、 神にとっては「やりたいこと」(主観的原理)が「やるべきこと」(客観的原理) と一致しているので神には義務とか命法とかは不要だが、 人間はこの二つが必ずしも一致しないので、 「やるべきこと」は命法と呼ばれるのである。
Everything in nature works according to laws. Rational beings alone have the faculty of acting according to the conception of laws, that is according to principles, i.e., have a will. Since the deduction of actions from principles requires reason, the will is nothing but practical reason. If reason infallibly determines the will, then the actions of such a being which are recognised as objectively necessary are subjectively necessary also, i.e., the will is a faculty to choose that only which reason independent of inclination recognises as practically necessary, i.e., as good. But if reason of itself does not sufficiently determine the will, if the latter is subject also to subjective conditions (particular impulses) which do not always coincide with the objective conditions; in a word, if the will does not in itself completely accord with reason (which is actually the case with men), then the actions which objectively are recognised as necessary are subjectively contingent, and the determination of such a will according to objective laws is obligation, that is to say, the relation of the objective laws to a will that is not thoroughly good is conceived as the determination of the will of a rational being by principles of reason, but which the will from its nature does not of necessity follow.
The conception of an objective principle, in so far as it is obligatory for a will, is called a command (of reason), and the formula of the command is called an imperative.
All imperatives are expressed by the word ought [or shall], and thereby indicate the relation of an objective law of reason to a will, which from its subjective constitution is not necessarily determined by it (an obligation). They say that something would be good to do or to forbear, but they say it to a will which does not always do a thing because it is conceived to be good to do it. That is practically good, however, which determines the will by means of the conceptions of reason, and consequently not from subjective causes, but objectively, that is on principles which are valid for every rational being as such. It is distinguished from the pleasant, as that which influences the will only by means of sensation from merely subjective causes, valid only for the sense of this or that one, and not as a principle of reason, which holds for every one.* *The dependence of the desires on sensations is called inclination, and this accordingly always indicates a want. The dependence of a contingently determinable will on principles of reason is called an interest. This therefore, is found only in the case of a dependent will which does not always of itself conform to reason; in the Divine will we cannot conceive any interest. But the human will can also take an interest in a thing without therefore acting from interest. The former signifies the practical interest in the action, the latter the pathological in the object of the action. The former indicates only dependence of the will on principles of reason in themselves; the second, dependence on principles of reason for the sake of inclination, reason supplying only the practical rules how the requirement of the inclination may be satisfied. In the first case the action interests me; in the second the object of the action (because it is pleasant to me). We have seen in the first section that in an action done from duty we must look not to the interest in the object, but only to that in the action itself, and in its rational principle (viz., the law).
A perfectly good will would therefore be equally subject to objective laws (viz., laws of good), but could not be conceived as obliged thereby to act lawfully, because of itself from its subjective constitution it can only be determined by the conception of good.
Therefore no imperatives hold for the Divine will, or in general for a holy will; ought is here out of place, because the volition is already of itself necessarily in unison with the law. Therefore imperatives are only formulae to express the relation of objective laws of all volition to the subjective imperfection of the will of this or that rational being, e.g., the human will.
--from FUNDAMENTAL PRINCIPLES OF THE METAPHYSIC OF MORALS BY IMMANUEL KANT (Translated by Thomas Kingsmill Abbott)