Lewis explains that there are three aspects of morality: social, individual, and ultimate purpose. That is to say, morality has something to do with each of these three things: (1) harmony between individuals, (2) harmony inside the individual, and (3) ultimate purpose, or beliefs about what the ultimate purpose of man is, or the relation between man and God who made him. (For the materialist, life has no ultimate purpose because everything ends at the grave; God doesn’t exist, so it doesn’t matter whether you live as a sinner or as a saint. For the Christian, life has ultimate purpose, because God exists, so our actions and decisions have eternal consequences and hence significance and meaning.)
The human person is a kind of “machine” and morality is kind of the set of instructions about how this machine should be run. It is not something that “prevents us from having a good time.” It is, rather, the only thing that can help us have a genuinely good, and thus joyful, time.
Morality is not just an “ideal” that some choose to pursue while others don’t. It’s actually something that everyone is called to observe because it is applicable to us all simply by virtue of our being human.
The human machine can morally “malfunction” in two ways: When individuals drift apart from one another or collide with one another; or when the different aspects of a person drift apart or collide inside him.