Now this is cool--a large group of scholars have organized a blog devoted to C.S. Lewis. You can find it here. Here is a smaple post about the Narnia series:
Ever since they were published in the 1950s, C.S. Lewis's seven Chronicles of Narnia have puzzled readers. The puzzle has to do with the fact that the seven stories have no obvious unifying theme.
Three of the books seem to be clear Biblical allegories. The Lion, the Witch and the Wardrobe is a retelling of the Gospel story. The Magician’s Nephew gives us a version of the creation account from the Book of Genesis. The Last Battle reimagines the end of the world and the final judgement, as told in the Book of Revelation.
But the other four Narnia Chronicles have no obvious scriptural foundation. Why does the Christ-like figure of Aslan enter the story among dancing trees in Prince Caspian? Why does he fly in a sunbeam in The Voyage of the ‘Dawn Treader'? Why is he mistaken for two lions in The Horse and His Boy? Why does he not appear in Narnia at all in The Silver Chair?
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To find the real solution to the mystery of Narnia's apparently haphazard symbolism, we need to look more closely at the professional interests of C.S. Lewis.
Although Lewis is best known for his Chronicles of Narnia, he was not a professional writer of fiction. His career was in the academic world. He taught at Oxford from 1924-1954, and for the last nine years of his life he was Professor of Medieval and Renaissance Literature at the University of Cambridge.
As a literary historian, Lewis had a particular interest in medieval cosmology. According to this old view of the cosmos, Earth was the centre of everything. It was circled by the seven planets in their spheres. Each of these seven planets was believed to possess particular characteristics and to exert special influences upon people on the Earth and even upon the metals in the Earth's crust. The place where Lewis writes most about this old cosmology is in his book, The Discarded Image.
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C.S. Lewis secretly based the Chronicles of Narnia on the seven heavens. The imagery associated with each planet provided him with his symbolic raw materials. The planetary symbols govern the shape of each story, countless points of ornamental detail and, most importantly, the portrayal of the central character, Aslan.
Read it all here.