This research revolves around the comparison of these two religions, their respective antecedents, and thus developmental lines. I will argue that a large number of similarities, particular parallel circumstances and religious developments, make the respective religions of the ancient Iranians and early Israelites more alike to one another than to neighboring religious societies. One of these similarities is the eventual development of monotheism in Zoroastrianism and Judaism. This is not to say that each religion expresses monotheism in identical fashion; as we shall see in Chapter 2, the differences between the theologies of monotheistic religions in the modern world support the notion that the religious framework connected with monotheism extends beyond a divine headcount. While many adherents of both Zoroastrianism and Judaism throughout history might identify as monotheists, there are still characteristics of each religion which complicate the seemingly simple effort of categorization.

Although the use of the name Zoroastrianism identifies it with the holy personage of Zarathustra (and a Hellenized spelling, at that), it is a religion which has long been characterized by the worship of Ahura Mazda. Consider the explanation of scholar of religions Jenny Rose: “Some adherents choose to refer to their religion by the ancient Iranian terms Mazdayasna ('worship of Ahura Mazda'), daena Mazdayasni ('the religion of Mazda worship') or daena vanguhi. This latter term, usually translated as 'the good religion', occurs in the Gathas, the oldest texts of the religion.”¹ In addition to acknowledging the various 'spirits' and other deities which have been (and continue to be) present to various extents in the belief system of Zoroastrianism, it is important to note the position of the deity as the focal point of worship in the ancient and modern religions. Philologist Almut Hintze argues against applying an Abrahamic, or biblical, definition of monotheism onto the religion² and suggests “...that Zoroastrianism has its own particular form of monotheism – which is the Zoroastrian way.”³ Skjærvø explains that categories of 'monotheism', 'dualism', and 'polytheism' have variously fit Zoroastrianism at different times throughout its history and he writes that “although stringent terminology is useful...categorizing seems less important than describing as accurately as possible the form of the system in the various periods.”⁴ Although the scholarly debate around such categorization cannot be concisely resolved within this writing, I will argue, in line with Skjærvø, that we must avoid overemphasizing the terminology of numeric monotheism as a shorthand for the belief, practices, and perspectives which belong to each religious system: I suggest that, in both religions, these aspects derive from monotheistic worldviews.⁵

There appears to be significantly less debate surrounding the eventual development of monotheism in the Jewish religion than in Zoroastrianism. This is not to say that the categorization of monotheism easily fits all aspects of Judaism – nor can it easily be applied to the (preceding) Israelite religion. It is cogent to this argument to acknowledge that the type of monotheism that is, (according to Hintze) by definition, a feature of Jewish and Christian religions is itself monotheism done 'a Jewish way' and 'a Christian way' respectively. I point this out to offer a reminder that the category must be defined by both the Zoroastrian and Jewish 'ways' of expressing monotheism. Because I will argue in this writing that the religion of the Israelites developed the kernel of monotheistic thinking which would be refined into the monotheism of Judaism, it is vital to remember that many aspects of the former made their way into the latter. Mark S. Smith notes: “...the Bible as a whole simply does not teach the existence of only one God.”⁶ Smith's comments point to the importance of the Hebrew Bible beyond its use as historical documentary of a long-dead people, but as the scriptural canon of a living religion in the modern world. Smith reminds us that however monotheistic Judaism (as well as Christianity and Islam) might be understood, the significance of a corpus of scripture which bears evidence⁷ of historical (numeric) polytheism in a modern context reveals the difficult of such categorization.