《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16节
In order indeed that a rational being who is also affected through the senses should will what reason alone directs such beings that they ought to will, it is no doubt requisite that reason should have a power to infuse a feeling of pleasure or satisfaction in the fulfilment of duty, that is to say, that it should have a causality by which it determines the sensibility according to its own principles. But it is quite impossible to discern, i.e., to make it intelligible a priori, how a mere thought, which itself contains nothing sensible, can itself produce a sensation of pleasure or pain; for this is a particular kind of causality of which as of every other causality we can determine nothing whatever a priori; we must only consult experience about it. But as this cannot supply us with any relation of cause and effect except between two objects of experience, whereas in this case, although indeed the effect produced lies within experience, yet the cause is supposed to be pure reason acting through mere ideas which offer no object to experience, it follows that for us men it is quite impossible to explain how and why the universality of the maxim as a law, that is, morality, interests. This only is certain, that it is not because it interests us that it has validity for us (for that would be heteronomy and dependence of practical reason on sensibility, namely, on a feeling as its principle, in which case it could never give moral laws), but that it interests us because it is valid for us as men, inasmuch as it had its source in our will as intelligences, in other words, in our proper self, and what belongs to mere appearance is necessarily subordinated by reason to the nature of the thing in itself.
注释摘要
这一段处于全书论证走到尽头之前的最后一里路。康德在前面已经把道德的最高原则归结为意志的自律，又把自律与自由绑定在一起——自由意志无非就是给自己立法的意志。但迄今为止，这一切都还停留在概念分析的层面。现在一个更棘手的问题逼上门来：就算我承认道德的公式，承认准则必须能够同时成为普遍法则，我凭什么要对这个法则感兴趣？我为什么要服从它？ 这个问题之所以尖锐，是因为…