An action is moral, said Kant, only if one has no desire to perform it, but performs it out of a sense of duty and derives no benefit from it of any sort, neither material nor spiritual. A benefit destroys the moral value of an action. (Thus if one has no desire to be evil, one cannot be good; if one has, one can.)

If there lurks in most modern minds the notion that to desire our own good and to earnestly hope for the enjoyment of it is a bad thing, I suggest that this notion has crept in from Kant and the Stoics and is no part of the Christian faith. Indeed, if we consider the unblushing promises of reward and the staggering nature of the rewards promised in the Gospels, it would seem that our Lord finds our desires, not too strong, but too weak. We are half-hearted creatures, fooling around with drink and sex and ambition when infinite joy is offered us, like an ignorant child who wants to go on making mud pies in a slum because he cannot imagine what is meant by the offer of a holiday at the sea. We are far too easily pleased.〔Lewis, 1–2.〕

But not only is disinterested morality (doing good "for its own sake") impossible; it is undesirable. That is, it is unbiblical; because it would mean that the better a man became the harder it would be for him to act morally. The closer he came to true goodness the more naturally and happily he would do what is good. A good man in Scripture is not the man who dislikes doing good but toughs it out for the sake of duty. A good man loves kindness (Micah 6:8) and delights in the law of the Lord (Psalm 1:2), and the will of the Lord (Psalm 40:8). But how shall such a man do an act of kindness disinterestedly? The better the man, the more joy in obedience.