Any scholarly investigation must begin with the definition of terms and for purposes of this writing the terms which must be defined at the outset are those describing the peoples whose societies and religions serve as comparative subjects for this study. Because the focus of this work concerns the origins of specific religions, the path of this argument begins with the chronologically latest peoples and works backward. The opposite path will be taken to explain the boundaries which will mark out the various religious societies included in this study. For the sake of clarity and simplicity, I offer the following list of terms:

1. Indo-Iranian: The Indo-Iranian religion has been reconstructed using textual evidence from early Zoroastrian and Vedic Indian religions of a “common linguistic and literary tradition, including that of oral religious poetry, [which] is evidenced in themes, concepts, terminology and the poetic syntax of the Gathas [early Zoroastrian texts] that echo those of the Rig Veda [early Vedic texts].”¹ For our purposes, it is important to consider that it is the Indo-Iranian religion which serves as the earliest comprehensible religious ancestor of the developmental lines which culminate in Zoroastrianism and Hinduism. Scholar of Iranian languages Prods Oktor Skjærvø notes the geography and period of the Indo-Iranians: “The closer relationship between the languages and literatures of the ancient Iranians and Indo-Aryans proves they were once a single people, who probably lived in Central Asia east and southeast of the Aral Sea as far back as the third millennium BCE.”²

2. Ancient Iranian: Within the lineage of development from the religion of the Indo-Iranians to Zoroastrianism, the ancient Iranian religion could be considered 'proto-Zoroastrianism'. For our purposes the ancient Iranian religion must be described as a development of the Indo-Iranian religion as it took on a particularly Iranian/Zoroastrian character and which can be contrasted with the Indo-Aryan/Vedic Indian religion.³ Skjærvø begins his book The Spirit of Zoroastrianism by identifying the earliest roots of Zoroastrianism in this ancient religious society: “...in the second millennium BCE among Iranian tribes in Central Asia.”⁴ Additionally, I will defer to Skjærvø's linguistic definition of the term 'Iranian': “Iranians are here defined as speakers of Iranian languages. These include the ancient languages Avestan, Old Persian, Middle Persian = Pahlavi, and others, from which modern Persian (Farsi), Kurdish, Pashto (Afghan), and many others are descended.”⁵

3. Zoroastrianism: For this research, I consider the development of the Zoroastrian religion, as we might know it today, to be the result of a developmental process which does not bear a definitive chronological marker as might be found in the origins of Christianity or Islam.⁶ The closest marker of transition from the religion of the ancient Iranians to Zoroastrianism could be associated with the composition of oral poetry/scripture attributed to the religion's 'prophet' Zarathustra.⁷ It is important to resist Jewish or Christian notions of reformation and prophet-centered religious revolution, for it would seem that the effort of Zarathustra produced both documentation, of a sort, of the religious culture which permeated his life as well as inspiration for developments toward what we might recognize as Zoroastrianism today. Scholar of religion Jamsheed Choksy describes the name and position of Zarathustra in the context of the ancient Iranian religion: “

In established Mazdean or Zoroastrian belief, Zarathushtra (later called Zarduxsht and Zardosht, also known as Zoroaster from the ancient Greek rendering Zoroastres) is acknowledged as the prophet who founded the Iranian religion of Mazda-worship now named after him. But, rather than viewing himself as a prophet or religious founder who created a new confessional community, Zarathushtra may have regarded himself as a devotional poet. In that role, he would have been continuing longstanding Indo-European and Indo-Iranian practices of praising order and certain spiritual entities associated with the maintenance of order while ascribing blame for disorder to other spiritual entities.⁸

4. Persian: I will begin the first chapter of this argument with a quote from Herodotus concerning the Persian religion. Although it is beyond the scope of this paper to delve into the fascinating discussion of whether or not all of the Achaemenid rulers, themselves, were Zoroastrian, it is sufficient for this study that Herodotus' observation of Persian religious custom, directly or indirectly, reveals a curious difference between Zoroastrianism and the neighboring polytheisms of the Near East. Skjærvø writes: “The Achaemenids (the dynasty founded by Cyrus the Great) were, to our knowledge, the first Iranians to use writing, inspired by their literate neighbors...The earliest known is the Bisotun (Behistun) inscription (520 BCE), in which Darius I (522-486 BCE) narrates how he came to power and united the Iranian lands...as well as his relationship with Ahura Mazd.”⁹ For our purposes, it is important to consider the presence and relevance of Zoroastrianism in “...three great Iranian [Persian] empires, the Achaemenids (550-330 BCE), the Arsacids/Parthians (247 BCE-224 CE), and the Sasanians (224-650).”¹⁰

5. Indo-Aryan: Skjærvø writes: “Their [that is, Iranian languages] closest non-Iranian relatives are the Indo-Aryan (Indic) languages (Sanskrit, Hindi, etc.).”¹¹ The religion of the earliest Indo-Aryan speakers serves, in this writing, in comparison and contrast to that of the ancient Iranians as it developed from the 'mother' religion of the Indo-Iranians. Before the Indo-Aryans moved into and through the Indus River Valley, their religious culture had individuated from that of the ancient Iranians: it belongs to a lineage in which we find the Vedic religion and eventually the modern Hindu religions of India.

6. Israelite: In contrast to the development lineage of Indo-Iranian, ancient Iranian, and Zoroastrian religions, there is a strong argument to be made that the pre-Jewish (defined below) Israelite religion existed, as such, before the late 6^th century BCE destruction of Solomon's Temple and the Babylonian Exile. Biblical scholar Glenn S. Holland describes the early history of the Israelites: “According to their own traditions, the Israelites first entered Syria-Palestine as nomadic herders of sheep and goats, living in autonomous family groups united by blood and a common allegiance to their god. The people later settled into agricultural communities and fortified cities, primarily in the central hilly country of Palestine and in the Jordan Valley, away from trade routes controlled by the Philistines and the Canaanite cities.”¹² Just as with Indo-Iranian society, it is difficult to be precise regarding the earliest history of the Israelites. For purposes of this research it is important to consider the history of the Israelites in two general phases: mobile and settled. I will argue that the earliest Israelite society was mobile and that settlement was as significant a change to the circumstances of the people and their religion as would be the eventual Exile.

7. Judaism: The Jewish religion is here considered to be that which developed after the destruction of the Temple, during the time of the Exile. Biblical scholar Mark S. Smith writes that some scholars “...including T. J. Meek, date the emergence of monotheism around the time of the “Exile” (587– 538). Faced with the prospect of overwhelming earthly powers, Judeans exalted their deity in absolute terms. There is no doubt that this camp has an easier task in criticizing those who hold an early date for monotheism.”¹³ Although I will argue that the roots of what would come to be understood as the monotheism of Judaism can be found in the monotheistic worldview of the Israelites, I must position my usage of the term Judaism in the camp which Smith describes. The period of Exile corresponds with a marked development (however we might characterize it) in the religion of the Israelites toward what we might recognize as Rabbinic (and eventually modern) Judaism.

In the way of defining one additional term, it is important to consider the use of the category of 'monotheism' as it might apply to Zoroastrianism or Judaism.