Religion scholar Huston Smith called Frithjof Schuon the most important religious thinker of [the 20th] century. In the first section of this revised edition of his classic work, Schuon provides striking insights to age-old religious and philosophical controversies such as the problem of evil, predestination and free will, and the meaning of eternity in heaven and hell. In the second section, Schuon masterfully harmonizes the divergent theological claims of the three main branches of ChristianityOrthodoxy, Catholicism, and Protestantismin the light of universal metaphysical truth. The final section contains several chapters relating to Islamic esoterism and concludes with a remarkable chapter on the spiritual substance of the Prophet. This new edition contains 60 pages of completely new material, including a fully revised translation from the French original and previously unpublished selections from Schuons letters and other private writings. Also included are editors notes, a glossary, and an index.