Thomas Aquinas (1224/6-1274) was one of the greatest of the medieval philosophers. His Summa Theologiae is his most important contribution to Christian theology, and one of the main sources for his philosophy. This volume offers most of the Summa's first 26 questions, including all of those on the existence and nature of God. Based on the 1960 Blackfriars translation, this version has been extensively revised by Brian Davies and also includes an introduction by Brian Leftow which places the questions in their philosophical and historical context. The result is an accessible and up-to-date edition of Aquinas' thoughts on the nature and existence of God, both of which have continuing relevance for the philosophy of religion and Christian theology.