《道德形而上学基础·第三节·从道德形而上学过渡到纯粹实践理性批判》第17节
The question then, "How a categorical imperative is possible," can be answered to this extent, that we can assign the only hypothesis on which it is possible, namely, the idea of freedom; and we can also discern the necessity of this hypothesis, and this is sufficient for the practical exercise of reason, that is, for the conviction of the validity of this imperative, and hence of the moral law; but how this hypothesis itself is possible can never be discerned by any human reason. On the hypothesis, however, that the will of an intelligence is free, its autonomy, as the essential formal condition of its determination, is a necessary consequence. Moreover, this freedom of will is not merely quite possible as a hypothesis (not involving any contradiction to the principle of physical necessity in the connexion of the phenomena of the sensible world) as speculative philosophy can show: but further, a rational being who is conscious of causality through reason, that is to say, of a will (distinct from desires), must of necessity make it practically, that is, in idea, the condition of all his voluntary actions. But to explain how pure reason can be of itself practical without the aid of any spring of action that could be derived from any other source, i.e., how the mere principle of the universal validity of all its maxims as laws (which would certainly be the form of a pure practical reason) can of itself supply a spring, without any matter (object) of the will in which one could antecedently take any interest; and how it can produce an interest which would be called purely moral; or in other words, how pure reason can be practical- to explain this is beyond the power of human reason, and all the labour and pains of seeking an explanation of it are lost.
注释摘要
这一段承担着一个非常沉重的任务：在全书论证即将收束的时候，康德明确地为人类理性划出一道边界。他问的是——绝对命令究竟怎么是可能的——然后他给的答案，一半是肯定，一半是断然的否定。这也是整个第三节最富张力的段落之一：它把此前关于自由与自律的全部推演，都引向一个理性无法再前进的极限点。 我们可以先拆解这一段的论证层次。第一个层次，康德承认，对于绝对命令如何可能…