The Critique of Practical Reason [18]
and is ready to use other people's money for the purpose as if it were his own, provided only he knows that he can do so safely, and without discovery; you would either believe that the recommender was mocking you, or that he had lost his senses. So sharply and clearly marked are the boundaries of morality and self-love that even the commonest eye cannot fail to distinguish whether a thing belongs to the one or the other. The few remarks that follow may appear superfluous where the truth is so plain, but at least they may serve to give a little more distinctness to the judgement of common sense. The principle of happiness may, indeed, furnish maxims, but never such as would be competent to be laws of the will, even if universal happiness were made the object. For since the knowledge of this rests on mere empirical data, since every man's judgement on it depends very much on his particular point of view, which is itself moreover very variable, it can supply only general rules, not universal; that is, it can give rules which on the average will most frequently fit, but not rules which must hold good always and necessarily; hence, no practical laws can be founded on it. Just because in this case an object of choice is the foundation of the rule and must therefore precede it, the rule can refer to nothing but what is [felt], and therefore it refers to experience and is founded on it, and then the variety of judgement must be endless. This principle, therefore, does not prescribe the same practical rules to all rational beings, although the rules are all included under a common title, namely, that of happiness. The moral law, however, is conceived as objectively necessary, only because it holds for everyone that has reason and will. The maxim of self-love (prudence) only advises; the law of morality commands. Now there is a great difference between that which we are advised to do and that to which we are obliged. The commonest intelligence can easily and without hesitation see what, on the principle of autonomy of the will, requires to be done; but on supposition of heteronomy of the will, it is bard and requires knowledge of the world to see what is to be done. That is to say, what duty is, is plain of itself to everyone; but what is to bring true durable advantage, such as will extend to the whole of one's existence, is always veiled in impenetrable obscurity; and much prudence is required to adapt the practical rule founded on it to the ends of life, even tolerably, by making proper exceptions. But the moral law commands the most punctual obedience from everyone; it must, therefore, not be so difficult to judge what it requires to be done, that the commonest unpractised understanding, even without worldly prudence, should fail to apply it rightly. It is always in everyone's power to satisfy the categorical command of morality; whereas it is seldom possible, and by no means so to everyone, to satisfy the empirically conditioned precept of happiness, even with regard to a single purpose. The reason is that in the former case there is question only of the maxim, which must be genuine and pure; but in the latter case there is question also of one's capacity and physical power to realize a desired object. A command that everyone should try to make himself happy would be foolish, for one never commands anyone to do what he of himself infallibly wishes to do. We must only command the means, or rather supply them, since he cannot do everything that he wishes. But to command morality under the name of duty is quite rational; for, in the first place, not everyone is willing to obey its precepts if they oppose his inclinations; and as to the means of obeying this law, these need not in this case be taught, for in this respect whatever he wishes to do be can do. He who has lost at play may be vexed at himself and his folly, but if he is conscious of having cheated at play (although he has gained thereby), he must despise himself as soon as he compares himself with the moral law. This must, therefore, be something different from