Manicheism, in its essential duality of good and evil, is much older than Manes. The earliest savages peopled the earth with spirits, some friendly, some hostile to man: the reduction of these friendly and hostile spirits to two several heads, and the neglecting to confess one, supreme over good and evil alike, (cf. Isa. xlv, 6, 7) was the genesis of Manicheism.
Of God and His Creatures: 1.42