Manichaeism, once the state religion of Persia and long a vigorous contender for converts throughout the ancient Near East, is best remembered for the simplicity of its teachings about divine power. For Manicheans, the universe was ruled by a Lord of Light and a Lord of Darkness, who fought continuously for supremacy. All that was good was a gift from the Lord of Light, and all that was evil was an affliction visited by the Lord of Darkness. This...