In the final part of his book, Lewis discusses theology, the “science of God.” Some might object that theology doesn’t really teach anything that matters about God—it’s more important to “feel” God spiritually than it is to understand how he works. But even if theology is no substitute for “feeling” God, it can still be a useful way to think about God and Christianity.
The final section of Lewis’s book concerns the “science” of religion (understood in a loose sense). While theology isn’t strictly necessary for being a Christian, it can help some people be better Christians by giving them an idea of how the transition from Earth to Heaven works.
One of the most surprising statements in all of Christianity is that by worshipping Jesus Christ, the Son of God, we too can become “sons of God.” In order to understand this statement fully, we need to look at it through a theological lens. In the Bible, we are told that Christ was “begotten, not created” by God. Connotatively, people “beget” things of the same kind as themselves; however, they “create” things that are not of the same kind. Thus, the phrase “begotten, not created” refers to the fact that Christ is, fundamentally, the same as God.
While some aspects of Christianity should be taken figuratively (for example, the idea that Heaven is a place with clouds and harps), Lewis argues that the notion that humans can become “sons of God” should be taken in a more literal sense: as we’re about to see, God will help good Christians move from base material life to a higher spiritual form of life.
When the Bible says that people become “sons of man,” it suggests that humans can assume the same kind of being as God, provided that they respect the rules of Christianity—they can change from something “created” to something “begotten.” Humans are capable of leading two different kinds of life—an ordinary material life, and a spiritual Christian life, the kind that God himself lives. Most people never get to lead the second kind of life, but if they worship God, they will. Lewis likens the relationship between ordinary and spiritual life to the difference between a statue of a man and a real, living man—when a Christian worships God, he undergoes a change as massive as if he were transformed from a statue into a real man.
Since the first chapter of Mere Christianity, Lewis has suggested that humanity is, by its very nature, sinful. Here, he builds on this idea by suggesting that humans can transcend their innate sinfulness by casting aside material things and worshipping Jesus Christ. The transition from materiality to spirituality (or, in another sense, from Earth to Heaven) involves nothing less than the discovery of a different kind of life. Lewis can only say so much about what this “new life” is like (since he’s not in Heaven yet), but he’ll attempt to analyze it in the following pages.