I have an actor friend, Joe Abbey-Colborne, who worked with me in campus evangelism nearly twenty years ago. When I first suggested a collaboration to him, he was nervous. He had had too many experiences of doing dramatic sketches, then having a preacher stand up and say, “Now, I hope you understand that this character represents Jesus, and that the lesson the sketch holds for us is the following.” I promised I would never do anything of the sort.
C.S.Lewis had similar worries about The Chronicles of Narnia. He was emphatic that the Narnia stories are not an allegory, like Pilgrim’s Progress, or even his own Pilgrim’s Regress, where a is meant to represent b, and c to represent d. They are rather, he suggested, a “supposal.” Suppose that the God who created our world created life on other planets, and suppose that this God chose to communicate with them, what that communication look like? Naturally, there would be similarities to our experience of God in our world—we might recognise something of the same flavour—the same style if you will—of God as we know God in Jesus Christ. And yet it would be distinctive.
As a result, with the exception of The Lion, the Witch and the Wardrobe, the first (and, I would argue, the weakest—he got better as he went along) of the books, while we may recognise Christian themes in Aslan’s dealings with the Narnian world (his loving strength, his demand for trust, his willingness to be intimate with his creatures), there are few one-to-one correspondences with the story of God as we know it.
His goal, he told his friend George Sayer, was “a sort of pre-baptism of the child’s imagination.” Sayer comments, “His hope was that when, at an older age, the child came into contact with the real truths of Christianity, he or she would find these truths easier to accept because of reading with pleasure and accepting stories with similar themes years before.” 
In a sense, Lewis is giving his readers the opportunity to follow the course of his own spiritual journey: raised in the Anglican church, but finding it lifeless, and turning instead to atheism; having experiences of “joy” through reading pagan mythology; and finally returning to Christian faith (and Anglicanism) by realising (with the help of his friend Tolkien) that the mythology he had loved was really pointing him beyond itself to a depth in Christianity—the true joy—that he had never known as a child. The Chronicles seek to circumvent the “watchful dragons” too often associated with “religion.”
Naturally, there are few hints in the Chronicles themselves that this is Lewis’ goal. That would be to subvert his intention—not to say ruin a perfectly good story. But in The Voyage of the Dawn Treader, he gives two very strong hints of what he is about.
One takes place when Lucy is in the magician’s house on the Island of the Voices, reading through the book of spells. She comes across a story “for the refreshment of the spirit,” which takes up three pages and tells “about a cup and a sword and a tree and a green hill.” She says, “That is the loveliest story I’ve read or ever shall read in my whole life.” Yet as soon as the story is done, she cannot recall it, nor can she turn the pages back. She asks Aslan, “Will you tell it to me, Aslan?” And he says, “Indeed, yes. I will tell it to you for years and years.” For the thoughtful reader, it raises the question of where Lucy might find such a story in our world. Christian readers already know.
The other place is right at the end of the book, when the children are about to return to their own world, and Lucy weeps because (she thinks) they will never see Aslan again. Aslan says, “But you shall meet me, dear one.” Edmund doesn’t understand: “Are—are you there too, sir?” To which Aslan replies:
“I am . . . But there I have another name. You must learn to know me by that name. That was the very reason you were brought into Narnia, that by knowing me here for a little, you may know me better there.”
Again, Lewis is putting a grain of sand into the oyster of the reader’s mind: what on earth is Aslan’s “other name” in our world? How can we possibly know the fictional Aslan in our own world? How can there have been a this-worldly “purpose” to our reading about Narnia? Lewis is not going to tell us: but he wants us to think about it, and (with the help of the Spirit) to discover the answer.
Lewis is a good evangelist—clear about The Story but respectful, winsome and imaginative in how he presents it, seeking a response and yet encouraging us to figure it out for ourselves. We could do worse than to follow his example. And maybe the movie—if it as faithful to the book as it is supposed to be—will be helpful to us in our own evangelism.
 Sayer, George, Jack: A Life of C.S.Lewis (Wheaton IL: Crossway Books, 1994), 318, 419-420.
 Lewis, C.S. “Sometimes Fairy Stories May Say Best What’s to be Said”, in Of This and Other Worlds (London: Collins Fount Paperbacks, 1984), 72.
 Lewis, C.S. The Voyage of the Dawn Treader (Harmondsworth: Puffin Books, 1965), 134, 137.
 Ibid., 209.