Before Lewis delves into more specifics about what constitutes the "Christian life," he explores the relationship between morality and psychoanalysis, both of which claim to "put the human machine right." This leads him to clarifying that Christian morality isn't a reward system for keeping rules but an acknowledgment that every one of our choices contributes to the growth of our central being "either into a creature that is in harmony with God, and with other creatures, and with itself, or else into one that is in a state of war and hatred with God, and with its fellow-creatures, and with itself."

Having discussed morality in general and the cardinal virtues (chapters 1 and 2 of Book 3), Lewis takes a look at Christian morality and contrasts it with society's desire for political programs and for "the Church" to lead the way. He comments on what a fully Christian society might look like, and the role of the individual in bringing it about.

Lewis expands on the previous chapter about morality to explore four specific areas (called the "Cardinal Virtues" by "old" writers) of morality.

What is morality? Is moral perfection an "ideal"? Lewis digs into these questions and proposes that there are three parts of morality.

Christ has undergone the perfect surrender and humiliation so that his life can be part of us. In this chapter, Lewis considers how that is to be done and entertains some objections to the Christian narrative.

What do Christians believe about the purpose of Jesus' life and death? Why was it necessary for God to become man and sacrifice his life in order to create a path for us to have a relationship with God who created us for relationship in the first place?

Is it in accordance with God's will that the Enemy has made himself Prince of this world? Lewis addresses the consequences of God's gift to us of free will and the ability to choose to put ourselves first. Lewis describes God's activity to keep the door open to a right relationship with him, including raising up a man who made the shocking claim of being able to forgive all sins, including those which were not made directly against him.

Having discussed atheism in the previous chapter, Lewis proceeds to examine the merits of Dualism (along with making a few observations about what he refers to as "Christianity-and-water"), the idea that there are two equal, independent forces behind our existence: a Good Power and a Bad Power.

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.

In this chapter, Lewis explores further what it means that there is a Somebody behind the Moral Law, sharing three thoughts for those who see his train of thought as the same old take on religion.