Mani, a third-century preacher, healer and public sage from Sasanian Mesopotamia, lived at a pivotal time and place in the development of the major religions. He frequented the courts of the Persian Empire, debating with rivals from the Judaeo-Christian tradition, philosophers and gnostics, Zoroastrians from Iran and Buddhists from India. The community he founded spread from north Africa to south China and lasted for over a thousand years. Yet the...