In Book 1, Lewis examines our concepts of right and wrong, following them to their logical conclusion: there is a being (that is very much like a mind) behind our Moral Law, and we are constantly making ourselves its enemy by choosing to disobey that law.

In Book 2, Lewis moves into a more specific consideration of what Christians believe. Chapter 1 looks at the difference between Pantheism (God is beyond good and evil, i.e., there is no "good" or "evil") and the Christian belief in a God who cares very much about the difference between good and evil.