The presence of Father Christmas [in The Lion, the Witch and the Wardrobe] bothered many of Lewis’s friends, including J.R.R. Tolkien. Tolkien, whose Middle-earth was free of the legends and religions of our world, objected to Narnia’s hodgepodge of motifs: the fauns and dryads lifted from classic mythology, the Germanic dwarfs and contemporary schoolboy slang lumped in with the obvious Christian symbolism.
But Lewis embraced the Middle Ages’ indiscriminate mixing of stories and motifs from seemingly incompatible sources. The medievals, he once wrote, enthusiastically adopted a habit from late antiquity of “gathering together and harmonizing views of very different origin: building a syncretistic model not only out of Platonic, Aristotelian and Stoical, but out of pagan and Christian elements.” . . .
The unifying principle of Narnia, unlike the vast complex of invented history behind Middle-earth, isn’t an illusion of authenticity or purity. Rather, what binds all the elements of Lewis’s fantasy together is something more like love. Narnia consists of every story, legend, myth or image — pagan or Christian — that moved the author over the course of his life.