That C.S. Lewis would write a book with a chapter entitled “Let’s Pretend” should surprise no one. Lewis often appealed to his readers to use their imagination, and the power of his own imagination was key to his coming to the faith.

For Lewis, the full use of the imagination does not divert us from the real or the true. Rather it has the opposite effect—stretching our muscles of invention expands the mind and the heart to better grasp what is real and what is true. In this sense, “Let’s pretend” is not an invitation to make believe but a door to enter a bigger world that awaits us.

I was not prepared for how much the “Let’s Pretend” chapter in Lewis’ classic Mere Christianity would do just that—stretch me, help me to grasp what was real and true about God and who I understood myself in relation to him. I had heard about Mere Christianity in my seminary days and learned about how it came about following a series of radio inputs by C.S. Lewis, addressing the people of England during the Second World War. It was recommended to me by a friend, and when I saw it in a bookstore shortly afterward, I bought it.

The first words of the foreword had me hooked: “This is a book that begs to be seen in its historical context as a bold act of storytelling and healing in a world gone mad.” “Sounds familiar,” I thought to myself. It went on to explain how Lewis believed that England, which had come to consider itself as post-Christian, had never in fact been told in basic terms what the religion is about.

Again, this struck a chord in me as being relevant to our modern age and in my own culture. So many seem to be rejecting Christianity without ever really knowing it. I read the contents page with interest at how Lewis ordered his chapters—not beginning with the God question but with the moral intuition of right and wrong as a clue to the meaning of the universe. The last of the four sections deals with the doctrine of the Trinity and contains the chapter that changed my life.

In the lead-up to the chapter “Let’s Pretend,” there were hints of what was to come. There were insights into the action of Christ in us that I had never had so clearly explained before. Lewis began to describe Christ with vivid imagery as someone who wants to come into your house and not to be left outside at a safe distance. However, letting him in promises to be both exciting and dangerous because doing so will change us.

In those previous pages, Lewis wrote: “The Christian thinks any good he/she does, comes from the Christ-life inside him”; “If you are thinking of becoming Christian, I warn you, you are embarking on something which is going to take the whole of you, brains and all.” He also talked about the life of Christ becoming active within us as a type of “good infection” and as “beginning to turn you into the same kind of thing as Himself. He is beginning, so to speak, to inject His kind of life and thought into you.” All of a sudden, the person of Christ became closer and even scary because he was ready and willing to change me.

Then, in the chapter “Let’s Pretend,” Lewis goes right to the heart of it with a message of incredible force:

Put right out of your head the idea that these are only fancy ways of saying that Christians are to read what Christ said and try to carry it out—as a man may read what Plato or Marx said and try to carry it out. They mean something much more than that. They mean that a real Person, Christ, here and now, in that very room where you are saying your prayers, is doing things to you. It is not a question of a good man who died two thousand years ago. It is a living Man, still as much a man as you, and still as much God as He was when He created the world, really coming and interfering with your very self; killing the old natural self in you and replacing it with the kind of self He has. At first, only for moments. Then for longer periods. Finally, if all goes well, turning you permanently into a different sort of thing; into a new little Christ, a being which, in its own small way, has the same kind of life as God; which shares in His power, joy, knowledge and eternity.

Here Lewis was describing the radical transformation that being Christian implies. Instead of a bland, unthinking faith, Lewis described the uniqueness of Christianity in terms that were dynamic and life-changing. Here is a religion that makes claims like no other because its founder changes us like no other. He changes us from within. He replaces dysfunctional parts of us with himself, turning us into “little Christs.”

The vocation of every Christian is to become a “little Christ” but only if we open every door of our lives to Jesus, invite him in, and allow him to do his work. It means that faith in Christ is not something fixed, but rather, in the words of Lewis, “in Christianity, God is not a static thing—not even a person—but a dynamic, pulsating activity, a life, almost a kind of drama.”

This insight of Lewis into our cooperation with the pulsating activity of grace and our participation in the great theo-drama provided me with a new language to understand both my own place in the world as a Christian and a confidence to preach and teach the faith in a fresh and compelling way. As a Christian, it brings me back to being “Christ-like”—not just believing in him but becoming like him by allowing him to work within me. But being like him does not come easy. It means daily conversion and change. This is why Christianity is so adventurous and yet challenging.

As a priest, Lewis’ words in this chapter continue to influence me. For example, in the confessional or in spiritual direction, I try to discern with people how the Lord is leading them to become more like himself, leading them toward his own thought, attitudes, and actions. The goal is deep inner conformity to Christ—not mere improvement but transformation. This is precisely what St. Paul describes in Galatians when he wrote: “It is no longer I who live but Christ who lives in me” (Gal. 2:20).

C.S. Lewis also keeps me focused, as a priest, on what my calling is all about—not primarily administration, maintenance, or management. Everything must be at the service of God’s people becoming more like Christ. For in Lewis’ words: “The Church exists for nothing else but to draw men and women into Christ, to make them little Christs. If they are not doing that, all the cathedrals, clergy, missions and sermons, even the Bible itself, are simply a waste of time.”

This chapter changed my life, and not only because it changed me and how I understand the life of grace. It also affected my ministry as a priest as well—to better understand God and his grace in a new and dramatic way. For this reason, I will be forever in debt to C.S. Lewis.