Now, it was with this dualism, this transformed survival of the sun and cloud myth, that the Jews came into association during their memorable exile in Babylon. Prior to that time their theology, as hinted above, had no devil in it. But in that belief in spirits which they held in common with all semi-civilised races, as a heritage from barbarous ancestors, there were the elements out of which such a personality might be readily evolved. Their _satan_, or "accuser," as that word means, is no prince of the demons, like the Beelzebul of later times; no dragon or old serpent, as of the Apocalypse, defying Omnipotence and deceiving the whole world; but a kind of detective who, by direction of Yahweh, has his eye on suspects, and who is sent to test their fidelity. In all his missions he acts as the intelligent and loyal servant of Yahweh. But although therefore not regarded as bad himself, the character and functions with which he was credited made easy the transition from such theories about him to theories of him as inherently evil, as the enemy of goodness, and, therefore, of God. He who, like Vritra, was an object of dread, came to be regarded as the incarnation of evil, the author and abettor of things harmful to man. Persian dualism gave concrete form to this conception, and from the time of the Exile we find Satan as the Jewish Ahriman, the antagonist of God. Not he alone, for "the angels that kept not their first estate" were the ministers of his evil designs, creatures so numerous that every one has 10,000 at his right hand and 1000 at his left hand, and because they rule chiefly at night no man should greet another lest he salute a demon. They haunt lonely spots, often assume the shape of beasts, and it is their presence in the bodies of men and women which is the cause of madness and other diseases.[28]
From the period when the Apocryphal books, especially those having traces of Persian influence, were written,[29] this doctrine of an arch-fiend with his army of demons received increasing impetus. It passed on without check into the Christian religion, and wherever this spread the heathen gods, like the _devas_ of Brahmanism among the Iranians, were degraded into demons, and swelled the vast crowd of evil spirits let loose to torment and ruin mankind.