The Muʿtazila was a school of rationalist Islamic theology, known as kalām, and one of the important currents of Islamic thought. Muʿtazilīs stressed the primacy of reason and free will, and developed an epistemology, ontology and psychology which provided a basis for explaining the nature of the world, God, man and the phenomena of religion such as revelation and divine law. In their ethics, Muʿtazilīs maintained that good and evil can be known solely through human reason. The present volume reflects some of the research by members of the “Muʿtazilite Manuscripts Project Group”.