Health, wealth, intellect, are good only insofar as they are used well.

Health, wealth, intellect, are good only insofar as they are used well. But the good will is good; it “shines forth like a precious jewel,” even if “through the niggardly provision of a stepmotherly nature,” the agent is insufficiently strong, rich, or clever to bring about desirable states of affairs. Attention is thus focused from the outset on the agent’s will, on his motives and intentions, rather than upon what he actually does. What motives or intentions make the good will good?

The good will’s only motive is to do its duty for the sake of doing its duty. Whatever it intends to do, it intends because it is its duty. A man may do what is, in fact, his duty from quite other motives. A shopkeeper giving the correct change may be honest not because it is his duty to be honest but because honesty pays off by bringing him custom and increasing his profits.

But it is important to note here that a will can fail to be good not only because duty may be done from self-interested motives but also because duty may be done from altruistic motives which nonetheless spring from inclination. If I am a friendly, cheerful, kind person by nature, who enjoys helping others, my altruistic acts, which may be what duty in fact demands from me, may be done not because duty demands them but just because I have an inclination to behave in this way-I enjoy it.

If so, my will fails to be decisively good, just as if I had acted from self-interest. Kant rarely mentions and never dwells upon the difference between inclinations to act in one way rather than another; the whole contrast is between duty upon the one hand and inclination of every kind upon the other. For inclination belongs to our determined physical and psychological nature; we cannot in Kant’s view choose our inclinations. What we can do is to choose between our inclination and our duty.

How, then, does duty present itself to me? It presents itself as obedience to a law that is universally binding on all rational beings. What is the content of this law? and how do I become aware of it? I become aware of it as a set of precepts which in prescribing to myself I can consistently will should be obeyed by all rational beings.

The test of a genuine moral imperative is that I can universalize it-that is, that I can will that it should be a universal law, or, as Kant puts it in another formulation, that I can will that it should be a law of nature.