Perhaps the most important thing to know about an imaginary world is how to get into it from this one. But C.S. Lewis' child characters can never predict how they will enter Narnia. In The Lion, the Witch and the Wardrobe, Lucy is investigating an almost empty wardrobe in an almost empty room. Pushing her way through some musty fur coats towards the back of the wardrobe, she feels the boarders of life in this world give way, and finds herself "standing in the middle of a wood at night-time with snow under her feet and snowflakes falling through the air." Thus Lewis begins the first-published of his seven Narnia chronicles; going on to craft in ever more detail the fabulous landscapes of his imaginary kingdom, drawing on classical mythology, fairy tales and the literature of chivalry to create the Narnian characters who are guided and protected by the lion Aslan, son of the emperor over the sea.

In The Voyage of the Dawn Treader, a picture in a bedroom becomes another opening into Narnia for Lucy, her brother Edmund and their cousin Eustace. Lewis's technique is to create a strongly realized situation from everyday life, so as to highlight the numinous moment when the children pass into their other world. He uses this technique most effectively in The Silver Chair, when Eustace and his friend Jill are being chased by bullies at their school Experiment House. They come to a door in a wall. This door is usually locked, but now when the desperate children try the handle, the door opens. Behind them stretch the grey skies of the moors around Experiment House, but Narnian sunshine pours through the doorway "as the light of a June day pours into a garage when you open the door."

All the children who visit Narnia have adventures there, but the story of Eustace's first visit reveals an aspect of the chronicles which has always been significant for religiously committed readers. Lewis's narratives fluctuate as we read them from the intimacy of the fairy tale to the grandeur of myth. They also manage to be at one and the same time aesthetically justified stories and parables of moral life. The integration of these various levels in Lewis's imagination is almost seamless.

In The Voyage of the Dawn Treader, Eustace is thoroughly disliked by his two Penvensie cousins, Edmund and Lucy, for the nastiness, cowardice and dishonesty he displays as the Dawn Treader makes its way through the Narnian seas. When the ship moors in the harbour of a large island, something very unexpected happens to Eustace. While wandering in a lonely valley, he finds himself transformed into a dragon.

Lewis handles the mythic theme of shape-changing superbly, but the aspect of his treatment I would like to discuss here is Eustace's re-transformation into a human boy. As a dragon, he is lying awake and wondering what will become of him, when he sees a huge lion coming towards him. Eustace does not know that the lion is Aslan. Aslan brings Eustace to a pool high in the mountains of the island, and tells him to undress and bathe. Eustace tries to work out how a dragon can undress, and decides that he can slough his dragon skin. So Eustace sheds his skin, and begins to enter the pool. But as he does so he finds that another layer of dragon skin has formed. He sheds this and leaves it beside the first skin on the grass. Entering the pool once more, he finds the same thing happening all over again. He despairs of freeing himself from dragon form, until Aslan says to him "You will have to let me undress you." Aslan cuts through the skin with his claws in a way that hurts Eustace, but finally this thickest, darkest dragon skin is lying on the grass beside the others and Eustace is a boy again.

This episode is both a highly effective piece of story-telling and a parable illustrating moral progress as a demanding, painful but above all continuous process. Eustace changes from a boy who is mostly bad into a boy who is mostly good. He achieves this, with Aslan's help, after repeated efforts to change, repeated failure, and the experience of despair. This model of moral progress resembles that worked out discursively in the essays of theologians such as Cardinal Newman. Newman wrote of faith as an always continuing development, and of his own never finished conversion.

The Narnia stories then, are examples of what Adrian Hastings has called "allegorical theology". The more these stories charm us, the more they teach us. Lewis establishes a symbiotic relationship between two art forms: narrative art and the art of living well. Generations of readers, both children and adults, are proof of his success.