Alister McGrath, in a chapter from his book C.S. Lewis: A Life writes about Lewis and the Chronicles of Narnia.
Lewis's growing realisation that children's stories offered him a marvellous way of exploring philosophical and theological questions--such as the origins of evil, the nature of faith, and the human desire for God. A good story could weave these themes together, using the imagination as the gateway to serious thinking.
The origins of the Narnia stories lay, Lewis tells us, in his imagination. It all began with an image of a faun carrying an umbrella and parcels through a snowy wood. Lewis's celebrated description of the creative process depicts it as unfolding from mental images, which were then consciously connected to form a consistent plot...
Yet Lewis did not really see himself as 'creating' Narnia. As he once commented, 'creation' is 'an entirely misleading term.' Lewis preferred to think of human thought as 'God-kindled,' and the writing process as the rearrangement of elements that God has provided. The writer takes 'things that lie to hand,' and puts them to new use. Like someone who plants a garden, the author is only one aspect of a 'casual stream.' ...Lewis drew extensively on 'elements' he found in literature. His skill lay not in inventing these elements, but in the manner he wove them together to create the literary landmark that we know as the Chronicles of Narnia (p.264).
As a writer, it is my desire to see the writing process as the rearrangement of elements that God has provided. The writer is not the creator but more of an artist, that takes the colors God has already provided, and firmly fixes the collected sayings; that are given by one Shepherd (paraphrase of Ecclesiastes 12:11).