Now looking at how Zoroastrianism influenced Judaism and how the concept of Yahweh was expanded, taking on a richer content. This was not an easy task because of the exclusivity of Judaism, so there must have been enough of a similarity between the two creeds to create an attraction with minimal resistance. In addition, it is possible that the loftier concepts of Ahura Mazda were already latent qualities of Yahweh simply waiting for an opportunity for expression. Certainly, the prophets who arose during the exile give evidence of this readiness to change Yahweh from an angry god demanding appeasement to a more personal god of wisdom, holiness, justice and love. The anthropomorphic Yahweh was giving way to the Yahweh of pure spirit; albeit, a spirit with an exclusive covenant with the Jews.
But along with this more mature comprehension of Yahweh which the Hebrews absorbed from the Persian Ahura Mazda, there also came an exposure to the problem of evil. Up to this point Judaism had no philosophy to explain the presence of evil. They believed that Yahweh, who was supreme over both good and evil, looked with favor on the good and punished the evil; but, there was no explanation for the source of evil. The books of the Old Testament written during and after the period of exile reveal how Judaism struggled with this new concept.
After the exile the Jews awoke to a realization of the spiritual, antagonistic powers of evil, as they had not known them before. It is not unlikely that the author of Deutero-Isaiah may be rebuking Persian dualism in the words, quoted above, "I form the light and create darkness, " etc.. An instance in the development of these ideas may be indicated in the books of Samuel and Chronicles, the former compiled several centuries before the latter. In Samuel, Yahveh is angry with Israel and moves David to number them. In Chronicles, Satan "provoked David to number Israel." (The conception of Satan in Zechariah, Psalms and Job we probably may attribute to foreign influence.) He is represented as planning man's ruin, causing ills and disasters, and even exercising a sort of government. But the Jewish dualism is different from the Persian in this, that Yahveh is never eclipsed or held in subjection even for a time. He is always supreme. The work of Yahveh's creation, as it is told in the early allegorical parables of Genesis, may be marred by the presence of evil, but neither here nor elsewhere is Yahveh's power limited. He is always stronger than Satan and all the powers of evil. Yahveh, too, existed before the evil came into being. The Jewish dualism was not complete. (George William Carter, Zoroastrianism and Judaism, The Gorham Press, Boston, 1918, pgs 53-54.)
And neither were the original teachings of Zoroaster completely dualistic, but by the time of the Jewish exile, Zoroastrianism had adopted the concept of the equality of good and evil along with their respective gods.95:6.5 Original Zoroastrianism was not a pure dualism; though the early teachings did picture evil as a time co-ordinate of goodness, it was definitely eternity-submerged in the ultimate reality of the good. Only in later times did the belief gain credence that good and evil contended on equal terms.
TUB has given us a remarkable revelation concerning the origin of evil but we must not forget about the evolution of the concept of good vs. evil because its discovery, long, long ago, was one of the most momentous events in the evolution of religion on this planet. It's discovery allowed for the idea that gods can be "all good" or "all evil", with the "all good" god finally emerging as the victor. Evolutionary religion still awaits this victory; revelatory religion realizes that it has already happened; and true religion knows that it never really existed in the first place. 87:4.5 When the doctrine of good and bad spirits finally matured, it became the most widespread and persistent of all religious beliefs. This dualism represented a great religio-philosophic advance because it enabled man to account for both good luck and bad luck while at the same time believing in supermortal beings who were to some extent consistent in their behavior. The spirits could be counted on to be either good or bad; they were not thought of as being completely temperamental as the early ghosts of the monospiritism of most primitive religions had been conceived to be. Man was at last able to conceive of supermortal forces that were consistent in behavior, and this was one of the most momentous discoveries of truth in the entire history of the evolution of religion and in the expansion of human philosophy.