For over half a century, scholars have labored to show that C. S. Lewis's famed but apparently disorganized Chronicles of Narnia have an underlying symbolic coherence pointing to possible unifying themes such as the seven sacraments, the seven deadly sins, and the seven books of Spenser's Faerie Queene. None of these explanations has won general acceptance, and the structure of Narnia's symbolism has remained a mystery. Michael Ward has finally solved the enigma. In Planet Narnia, he demonstrates that medieval cosmology, a subject that fascinated Lewis throughout his life, provides the imaginative key to the seven novels. Drawing on the whole range of Lewis's writings, including previously unpublished drafts of the Chronicles, Ward reveals how the Narnia stories were designed to express the characteristics of the seven medieval planets—Jupiter, Mars, Sol, Luna, Mercury, Venus, and Saturn—planets which Lewis described as spiritual symbols of permanent value and especially worthwhile in our own generation. Using these seven symbols, Lewis secretly constructed the Chronicles so that in each book, the plotline, the ornamental details, and most importantly, the portrayal of the Christ-figure of Aslan all serve to communicate the governing planetary personality. The cosmological theme of each Chronicle is what Lewis called 'the kappa element in romance,' the atmospheric essence of a story that is everywhere present but nowhere explicit. The reader inhabits this atmosphere and thus imaginatively gains knowledge of the spiritual character that the tale was created to embody. Planet Narnia is a ground-breaking study that will provoke a major revaluation not only of the Chronicles but of Lewis's whole literary and theological outlook. Ward uncovers a much subtler writer and thinker than has previously been recognized, whose central interests were hiddenness, immanence, and knowledge by acquaintance.