From a review by Peter Brown in the New York Review of Books of “The Nativist Prophets of Early Islamic Iran: Rural Revolt and Local Zoroastrianism” by Patricia Crone (Cambridge University Press):

…As [Crone] presents it, Zoroastrianism as practiced preserved one basic principle: the world was good. It was good because it was suffused with an energy of light that was a direct continuation of the energy of God himself. As Crone puts it with memorable crispness: to Zoroastrians, the light of the sun and of the holy fires that they worshiped was not a symbol—it was a sample. It was a living piece of God. A world permeated with so precious a substance had to be kept pure. The safety of a divine order, fully present in the here and now, was at stake in every aspect of nature and of human society.

This amounted to a call to action. A Zoroastrian was a militant for the right order of things. Given the ravages of a constant, opposing force of evil, the order of things had to be defended and restored by means of constant efforts of reform. The world demanded not flight but perpetual vigilance, even social engineering. Only in this way would creation recover its original, undamaged radiance. It would shine again like gold, “excellent, without decay.”

And the Zoroastrians of the villages had no doubt as to how this radiance would be restored—by community of property combined with equal access to women. To outside observers, Christian or Muslim, this seemed either hilarious or obscene: “abstemious wife-sharing is always reported as if it were a merry free-for-all.” But this was not how the villagers saw it. What mattered for them was how to keep together the precious deposit of family land. For family land to break up; for each portion to follow a separate household; worse than that, for these portions to be irrevocably lost to outsiders, through the violence of the powerful and the pressure of agrarian debt: this was the sure way to impoverishment and the death of the village. Polyandrous marriage was the solution. For the Zoroastrians of the village, only a community of women could maintain the divine integrity of the land.

In reflecting on these topics, many Zoroastrians proved themselves to be far from boneheads. They examined the origins of private property with considerable moral rigor. They claimed that private property had been caused by the cold, life-denying impulse of “desire”—by an antisocial lust for land. They also denounced the swaggering “resource polygyny” of the nobility—the corralling of women as wives and concubines at the expense of potential non-noble spouses. Both desires caused “envy.” And envy lay at the root of the conflicts that destroyed the harmony of God’s creation. This was what a shadowy intellectual, Zardūsht son of Khrōsak, had thought already in the mid-third century. These ideas were taken up by Mazdak in the 530s. As a result of the preaching of Mazdak, a protracted jacquerie rocked the Iranian plateau. The villagers emptied the granaries and the harems of the nobility, until the Mazdakites were suppressed with exemplary (and much-praised) savagery by the great shah Khosrau I (531–579).