This volume examines the approaches of Fakhr-al-D n al-R z (d. 1209) and Thomas Aquinas (d. 1274) to the question of the eternity of the world, which was one of the most heated issues of debate between theologians and philosophers in the Middle Ages.The first chapter of the book gives some background to the discussion from Greek philosophy, early Judaeo-Christian and Muslim traditions. The second and the third chapters discuss the approaches of R z and Aquinas respectively to the question of the eternity of the world. The last chapter compares their approaches, brings out some similarities of their approaches between them as well as in relation to their own traditions, Islam and Christianity respectively.The book tries to show that though they were theologians, both R z and Aquinas were more in line with the philosophers than their fellow theologians.