"The Ikhwan al-Safa' or Brethren of Purity were a highly secretive group of tenth-century Shi'ite thinkers, their identities remaining unclear even today. Renowned for creating the legendary Rasa'il Ikhwan al-Safa', an encyclopedia of philosophical sciences, they proposed a coherent intellectual system that sought to reconcile human reasoning with prophetic revelation. With a spirit of tolerance uncommon to the era and an exceptional eclecticism of sources, their encyclopedia was popular and yet highly contentious, often characterized as heretical by Islamic theologians and leaders throughout history." "This fascinating survey provides a clear, objective and innovative introduction to the Brethren of Purity and their encyclopedic project, showing its critical place in the history of Arabic science, philosophy, and literature. Containing an illuminating guide to further reading and full of insight on the interpretation of the great work, this study will appeal to readers of all backgrounds."--BOOK JACKET.