Nature and spirit, that is, matter and spirit are thus united to form the cosmos, and the cosmos is the ‘Wheel’, the heavenly sphere, the embodiment of the finite Zurvan. As the Infinite, Zurvan is the father of both Ohrmazd and Ahriman; as the finite he is the weapon of the one as well as of the other. Thus the ‘weapons’ he gives his sons are himself in finite form. All that is good in him he gives to Ohrmazd; what is evil he gives to Ahriman, for Az is not only concupiscence, greed, and lust, it is also Varan, which means not only sexual desire but also religious doubt. Az, then, in this myth, must represent Zurvan’s doubt -that essential imperfection which lurked deep down in the godhead and, in the course of what perhaps we should call ‘aeveternity’, took shape and materialized in the form of Ahriman. Zurvan expiates his original sin by becoming embodied in the cosmos and suffering the evil effects of his sin to work themselves out in his own body. In this he, as macrocosm, prefigures the fate of each individual man; and just as he controls human destinies, so does the collective consciousness of mankind -the union of the Fravashis or external souls -control him.
– R.C. Zaehner, iranchamber.com