The aspects of Judaism regarded as integral to the developmental histories of Islam and Christianity are generally acknowledged and appear to have contributed its being deemed monotheistic. In contrast, the debate on Zoroastrian “monotheism” appears to have continued since before the Muslim conquest of the Sassanian empire more than 1300 years ago. The “problem” of monotheism, for theologians encountering Zoroastrianism, actually appears to be a “solution” to a familiar problem in “monotheistic” theologies: why does an omniscient, omnipotent, and omnipresent deity allow bad things to happen? Sometimes called “dualism,” Zoroastrian cosmology includes an acknowledgement of (and explanations for) the “chaos” that exists beyond, and in contrast to, “order.” This allows Ahura Mazda to be associated with only “good,” “true,” and “orderly” things, whereas the opposite of these things cannot, by definition, be associated with the deity. The eventual personification of those opposite concepts, in the form of Angra Mainyu, has been looked to as influential in Christian and Muslim constructions of “Satan.”¹ Like the presence of other deities in the Hebrew Bible, the figure of “the devil” or “Satan” in these cosmologies seems to have given rise to any number of explanations (and terms) for defining monotheism “despite.” The case of Zoroastrianism reveals that the criteria for deeming religions monotheistic may not just include shared answers, but shared questions.²