Lewis begins by noting several overly simplistic ideas about morality—for example, that it is primarily something meant to interfere with people’s lives rather than to help them. He also suggests that it’s problematic to talk about moral “ideals”; while it’s true that moral perfection is an “ideal,” the term can also reflect differences in tastes and goals. This is not a bad thing in itself, but we must be wary of treating morality as though it were subjective.

Lewis suggests that there are three components to morality: fairness and harmony with others, inner harmony, and humanity’s general purpose. He observes that people often focus on the first element when they talk about striving for Christian standards—partly because interpersonal conflict is readily apparent, and partly because there’s broad consensus about how we should treat other people. Nevertheless, Lewis cautions that laws are not sufficient to make good human beings—goodness must also come from within.

As for the third element, Lewis emphasizes the Christian view that every human being is granted eternal life; humanity’s ultimate “purpose” is therefore intertwined with its relationship to its creator, and things that we might not otherwise concern ourselves with become more serious. If a bad temper gradually gets worse, for instance, then what will it be like in a million years’ time? Furthermore, what effect does allowing this kind of flaw to fester have on an individual’s relationship with God? Lewis suggests that it is within this third area that we can find the key differences between Christian and non-Christian morality.