Abstract: As a scholar of medieval and renaissance literature, C.S. Lewis was deeply interested in the imaginative effects of the new heliocentric model of the universe theorised by Copernicus and verified by Kepler and Galileo. As a writer of fiction, Lewis held that success in imaginative composition came through suggestion rather than through statement; a good story's principal achievement was the atmosphere which it allowed the reader to inhabit, an atmosphere which should constitute the reader's mode of attention, not the reader's focus of attention. In his Chronicles of Narnia (The Lion, the Witch and the Wardrobe; Prince Caspian; The Voyage of the ‘Dawn Treader’; The Silver Chair; The Horse and his Boy; The Magician's Nephew; The Last Battle), Lewis drew upon his academic expertise in Ptolemaic astronomy and astrology, constructing each story so that it embodied and expressed the qualitative atmosphere associated with one of the seven planets of the pre-Copernican cosmos (respectively, Jupiter; Mars; Sol; Luna; Mercury; Venus; Saturn), planets which he described as ‘spiritual symbols of permanent value’. In each Chronicle, the arc of the narrative, countless points of ornamental detail, and the portrayal of the Christological figure of Aslan, are all governed by this cosmologically based imaginative intention. The Chronicles therefore are not, first and foremost, Biblical allegories, as critics have previously assumed, but attempts to communicate seven ancient archetypes through the genre of romance. The occasioning of the first story is argued to be the famous debate at Oxford's Socratic Club in which Lewis's Christian Idealism was critiqued by the philosopher, Elizabeth Anscombe. In sum, Planet Narnia contends that the Chronicles are the product of a subtler writer and thinker than has hitherto been recognised, whose abiding interests were hiddenness, immanence, and knowledge by acquaintance.

Keywords: planet, atmosphere, astrology, Jupiter, Mars, Sol, Luna, Mercury, Venus, Saturn