Designed as an introduction to the ideas of the Ikhwan, and employing an admirably succinct and lucid style, this book examines the writings of the Brethren, analyses the impact on them of thinkers such as Pythagoras, Plato, Aristotle and Plotinus, and locates their thought at the very heart of the medieval cauldron of Islamic Aristotelianism and Neoplatonism. It argues, controversially, that while the Brethren were profoundly influenced by Isma'ili thought, they were not themselves actually members of the Isma'ili sect of Islam.