Both resolve themselves on examination into mere figures of speech--phantoms of poetic imagery--abstract notions, clothed by language with an apparent, not a real, personality.
It was natural that, as time went on, Dualism should develop itself out of the primitive Zoroastrianism.

Language exercises a tyranny over thought, and abstractions in the ancient world were ever becoming persons.

The Iranian mind, moreover, had been strack, when it first turned to contemplate the world, with a certain antagonism; and, having once entered this track, it would be compelled to go on, and seek to discover the origin of the antagonism, the cause (or causes) to which it was to be ascribed.

Evil seemed most easily accounted for by the supposition of an evil Person; and the continuance of an equal struggle, without advantage to either side, which was what the Iranians thought they beheld in the world that lay around them, appeared to them to imply the equality of that evil Person with the Being whom they rightly regarded as the author of all good.

Thus Dualism had its birth.