What can or can't God do? What flexibility is there in the precise manner by which he executes his decrees? This book is a readically new interpretation of one of the key concepts of medieval religious philosophy: the concept of the power of God. In it Dr Moonan provides a thought-provoking and illuminating analysis of the arguments advanced by the medieval schoolmen to tackle this problem, concentrating in particular on the distinction they made between `absolute' and `ordained' divine power. In doing so, Dr Moonan brings to light some challenging and important new insights on the work of some of the most important thinkers of the Middle Ages - particularly Albert, Bonaventure, and Aquinas. Dr Moonan also discusses the secular predecessors who influenced these theologians, hitherto, largely overlooked by modern scholars, and as well as tracing the development of their ideas, he advances the case for their relevance and central position in modern religious philosophy today. This is a stimulating and ground-breaking book, which will not only help to clarify one of the notorious puzzles of medieval religious philosophy, but also provide an important challenge to theologians and philosophers today.