en the principles of good and evil,
(2) that the human soul is both the prize to be won by this war and the battleground upon which this war is fought,
(3) that the duty of human beings is to choose to be on the side of good, which will ultimately prevail.
The good is embodied in the god Ahura Mazda, which means "the good lord"; the name later wore down to the form Ormuzd. Evil is embodied in the spirit Angra Mainyu, which means "the evil spirit"; this name later wore down to Ahriman. The two were conceived as being almost equal and opposite; everything about Angra Mainyu is a dark, distorted parody of Ahura Mazda's characteristics--and this is apparently the source of the later Christian concept of Satan as the "ape of God."
Zoroastrianism was not, however, ultimately dualistic; it was, in fact, history's first great monotheistic religion. A central belief was that, although the war would last for ages, finally Ahura Mazda would prevail, and the forces of Angra Mainyu would be either destroyed or redeemed. (One can see an ultimate source for some Christian beliefs, such as that in the Last Judgment, in these Zoroastrianism concepts.) The Parsis of India were the last enclave of Zoroastrianism, having fled there after the onslaught of militant Islam. The beliefs of recent Parsi immigrants to America, where their faith community is growing very rapidly (they were not allowed to proselytize in India and were in danger of dying out), show that their concepts are no more dualistic than those of any other monotheistic religion.
Manichaeism, in contrast, was absolutely and ultimately dualistic. Mani (crucified by a Persian emperor about A.D. 275) took the Zoroastrian concept of opposing spiritual principles and defined them as absolutely equal and opposite, never able to overcome one another. He also divided ordinary reality in half, defining all that is spiritual and abstract as being on the side of the good, all th...