Dualistic religions form a spectrum from the extreme and absolute of Zoroastrianism, becoming more and more attenuated through the Zoroastrian heresy Zervanism, Gnosticism, and Manicheism to Christianity, Judaism, and Islam, where dualism almost ceases to exist. All these religions, however different from one another, stand together in their distance from monism. All posit a God who is independent, powerful, and good, but whose power is to a degree limited by another principle, force, or void. The dualism of Zoroastrianism or of Manicheism is overt; that of Judaism and Christianity is much more covert, but it exists, and it exists at least in large part owing to Iranian influence. The dualism of Christianity and that of Iran differ in one essential respect. The latter is a division between two spiritual principles, one good and the other evil; Christianity borrowed from the Greeks the idea that spirit itself is considered good, as opposed to matter, which is considered evil. But the dualism introduced by Zarathushtra was a revolutionary step in the development of the Devil, for it posited, for the first time, an absolute principle of evil, whose personification, Angra Mainyu or Ahriman, is the first clearly defined Devil.
(Jeffrey Burton Russell, The Devil: Perceptions of Evil from Antiquity to Primitive Christianity [Ithaca and London: Cornell University Press, 1977], 99 [footnote omitted])
Keith Burgess-Jackson, J.D., Ph.D. 