Religion in the Achaemenid Empire is a complex topic that forces one to confront a challenging set of sources, themes and arguments (Henkelman 2008, 60-63; Kellens 2017). The Empire's multi-ethnic structure, the Achaemenids' adoption of older imperial structures and capitals, and the traditional concept of place-bound divinity led to a plethora of co-existing practices and deities in the Empire. Texts created by the imperial administration and Greek outsiders, archaeological remains and epigraphically attested proclamations of the Great Kings all provide important clues in reconstructing the views and practices the Achaemenid Persians and the people of the Empire held and performed in relation to the gods. As with Achaemenid history in general, the key problem is that one is forced to rely on Greek authors, in particular Herodotus, for a fleshed out framework that allows one to make sense of the extant Achaemenid evidence. While it is generally agreed now that Herodotus (1.131f.) is at the very least misleading in his presentation of "Persian religion" (Waters 2014, 153f.), the interpretation and relative weight of the divergent and lacunose information given in the sources remains controversial. The following will focus on the controversies surrounding the aspects of religious worldview that a reader may encounter in the Achaemenid royal inscriptions and attempt to contextualise their account of religious thought and practice.
Despite some Greeks' literary exaggerations (e.g. Aesch. Pers. 156; cf. the more precise line 857), the Achaemenid kings were not gods, nor did they lay claim to divine origins. The royal inscriptions do, however, proclaim what may be best described as a symbiotic relationship between the king and a supreme creator-god called Ahura Mazda (Briant 2002, 240-254). Ahura Mazda accordingly takes precedence in many of these texts, which often open with a formula of exaltation and invocation. On the one hand, the Achaemenids are kings vašnā Auramazdāha, "by the favour of Ahura Mazdā", and on the other hand, Ahura Mazda "belongs" to the king (manā Auramazdā Auramazdāha adam; DSk). This supreme imperial god "bestowed the empire" (xšaçam frābara) on the kings. As these and similar expressions show, the Achaemenids' reign is legitimized by the gods, and the king is invested by them; i.e., he is their elect and their representative on earth (Gnoli 1974; Schmitt 1983).
Since Ahura Mazda is the main god of Zoroastrianism, one of the main points of contention has traditionally been "whether the Achaemenids were Zoroastrians", a question that is certainly too binary in that form (Knäpper 2011; Kellens 2017). Zoroastrianism, named after the Iranian priest Zarathustra/Zoroaster, whose dates remain disputed (1400~600 BCE; Boyce 1975, 190; Briant 2002, 93; Waters 2014, 152f.), was the dominant religion of pre-Islamic Iran, but it developed gradually over time in ways we cannot fully reconstruct. It adheres to a dualistic worldview, in which the forces of good and evil are locked in conflict. Zoroastrians worship Ahura Mazda, the "wise lord", as the supreme deity and creator of the earth and life. Through the spenta mainyu (the "benevolent/holy spirit") he fills the world with all that is good and truthful; its counterpart is the angra mainyu ("evil spirit") that breeds illness, corruption and death. Humanity is embroiled in this struggle between light and dark. Empowered to recognize the good creations of Ahura Mazda, humans can contain, but also succumb to the forces of evil. A binary pair of concepts, arta ("truth") and drauga ("lie"), derives from this same fundamental model and plays an important practical role in the life of believers and in the Zoroastrian liturgy, as does the division of the Iranian pantheon into good gods (ahuras) and bad gods (daevas) who exist in addition to Ahura Mazda (Hdt. 3.72; DB §52-55; DPd §3; Wiesehöfer 1994, 143f.).
Our written source material for this mature, vaguely monotheistic and dualistic Zoroastrianism was compiled in the Sassanian period (3rd~7th century CE, probably in the 4th century CE), but its development was then hampered by the spread of Islam. All extant manuscripts of this material hence derive from a single 9th century manuscript (Hoffmann/Narten 1989, 34-37; Kellens 1991, 107f.; Briant 2002, 93f.; Wiesehöfer 1994, 141). Its historical use is complicated by the fact that the Parthians and Sassanians, under the latter of which Zoroastrianism was clearly the dominant religion (Wiesehöfer 1994, 266f.; see for the complexity of religion in Iran under the Sassanians Boyce/Grenet/Beck 1991, 51-68) used Achaemenid models to legitimate themselves, and thus had an interest in creating continuity between themselves and the past (the Arsacid dynasty of the Parthian empire, founded by Arsakes I. in 247 BCE (Iust. 41.4-5), claimed to derive their lineage from Arsakes/Artaxerxes II (Georgius Syncellus 1.539.16-18 Dindorf); other points of contact are provided by the relief landscapes at Behistun and at Naqsh-i Rağab; Wiesehöfer 1994, 175f., 220f.). The only actual points of contact between the Sassanian Zoroastrian texts (including the Avesta) and the Achaemenid royal inscriptions are the name of the god Ahura Mazda and their focus on a „Manichean" worldview based on arta (truth) and drauga (the lie) (but cf. Skjærvø 1999, who detected further parallels). The inscriptions insist that the king, as the defender and embodiment of truth, upholds this order and defeats the lie with the aid of Ahura Mazda (e.g. DNa §5f., DNb, DPa, XPb). There is no mention of Zoroaster in the epigraphic or archival material, though when he first occurs in a probably authentic dialogue by the Greek philosopher Plato (Plat. Alc. 1, 122a; 4th century BCE), he is already connected to the Magi and their teachings on how to respect and care for the gods – note the plural. The language of the different layers of extant Zoroastrian texts and the Old Persian inscriptions further shows dialectal differences, indicating difference in their cultural and geographical provenance within Iran (Eastern vs. Western Iran; see Boyce 1975, 189 and for other such differences Jacobs 1987). In sum, the evidence weakens the case of those scholars wishing to declare the Achaemenids from Darius I onwards Zoroastrians in any clearly defined sense, i.e. in a codified form expressly linked to a founder figure.
The hypothesis that the Achaemenids were Zoroastrians is further weakened by the documentary evidence. While the great god of Mazdaism, Ahura Mazda, is clearly attested in the epigraphic material, there is no evidence for any significant practical cult of Ahura Mazda in the archives of Persepolis, which attest traditional, location-based religious pluralism instead (Henkelman 2008, ch. 3 & 304; Waters 2014, 151). The simple fact that Ahura Mazda is hardly mentioned in the Persepolis archives shows this quite clearly and always provided a significant obstacle to attempts to make the early Persian kings Zoroastrians. While Heidemarie Koch attempted to account for this problem by interpreting the most prominent offering found in these archives, the lan, as an offering to Ahura Mazda, and also considered other arguments, such as Ahura Mazda being unknown to the Elamite scribes or that worship of Ahura Mazda was an exclusive affair (Koch 1977; 1987; cf. also Knäpper 2011), Wouter Henkelman has shown persuasively that the tablets reflect the true realities of a multi-ethnic Empire (2008): "[I]t is not the corpus of inscriptions (and reliefs) that should inform us how the tablets should be understood [...]; it is the solid evidential basis of the archives that enables a new, broadly contextualized reading of the ideologically-charged inscriptions and the monumental iconography." (Henkelman 2017, 303).
The other gods (baga), to whom offerings were made by royal order or at least through the imperial administration, were hence not merely tolerated alongside the Zoroastrian deities (Kuhrt 2014). Instead, 'Achaemenid religion' was a synthesis of Persian, Median and Elamite elements. Given the epigraphic evidence from Babylon of Marduk, the highest local god, being named where Ahura Mazda occurs at Behistun (Voigtlander 1978, 63-65; Seidl 1999a+b; Rollinger 2016, 123; Waerzeggers 2015; the same can be said for Elamite Humban, who is most prominent in the Elamite area of Persepolis: Henkelman 2017), one should thus proceed on the assumption that Ahura Mazda was significant mainly in the context of ostentatious imperial communication to Persians, with the king adopting local religious roles of kingship throughout the Empire to demonstrate his piety and his role as mediator between the divine and the mundane world (Frye 1984, 120-123). Like these local roles, Ahura Mazda had a legitimizing function as the god of the king of kings (DNa §5; DNb §10; DSk). He provided the foundation of the empire's preconditions (earth, humanity and its happiness), its existence (by empowering the king to rule), its unity (by providing norms for the king to rule by), and continuity (by empowering the successors to take over and defeat their challengers).
Xerxes' notorious daiva inscription (XPh), in which he presents himself as destroying a sanctuary of evil gods (daiva) and enforcing worship of Ahura Mazda, should thus be interpreted in the light of this worldview. Adhering to Achaemenid rule and governance constituted 'worship' of Ahura Mazda in itself. The gods of rebels hence become daiva through the act of rebellion and the violation of arta it constituted (cf. DB §72). There is no evidence to support the argument that any actual cult of Ahura Mazda was ever imposed upon subject peoples by Xerxes, be it after the 'destruction' of the temple of Marduk at Babylon, the razing of the Acropolis at Athens (Ahn 1992, 111-113; Waters 2014, 118f., 156). Instead, as the Xanthos stele (TL 45 = TAM I 45) and the Babylonian copy of the Behistun inscription suggest, Ahura Mazda would simply, in an interpretatio Persica, be identified with the main, paternal deity of each local unit of the Empire, as long as the ethnos of this area remained loyal. We should hence not assume that Xerxes did anything out of the ordinary; he simply phrased traditional behaviour exhibited by Near-Eastern kings, i.e. presenting political disorder as religious destruction and neglect, which is remedied by the king's actions, in Mazdean terms (cf. e.g. DB §14; ABC 7.ii; C²Ba l. 1-8; Arr. Anab. 7.17.2; BM 36613 l. 8-10). All this served to communicate the king's charisma, which found expression in his relationship to the gods and the order of the land.
The elemental dimension of religion in the Achaemenid Empire, attested first and most prominently by Herodotus (Hdt. 1.131, 7.54; Curt. 3.3.8-11; Strab. 13.3.13f.), is never mentioned in the texts of the inscriptions. It does, however, seem to have contributed to where they were placed, as is suggested by the water cult in evidence in the gully above the spring and pool of Behistun (forthcoming; cf. Rollinger 2016), and their iconography, e.g. the fire altar depicted on Darius' tomb at Naqsh-i Rustam (Schmidt 1970, 80-87). The elemental strand of religious practice is prominent in specifically Zoroastrian beliefs (Boyce 1982, 113), but is demonstrably ancient (Boyce 1975, 150-156).
Ancestor worship is also attested, probably from Cambyses onwards (Arr. Anab. 6.29.7), but makes no appearance in the inscriptions beyond the general emphasis on dynastic continuity. The monumental cruciform tombs that are reliably identifiable down to Darius II have been interpreted as giving physical expression to beliefs in elemental purity, which are attested also in Herodotus (Hdt. 1.187; Boyce 1982, 111f.). The tombs can be interpreted as protecting elemental air, water, fire and earth from contamination by the dead matter of the corpse, which has polluting effects and is associated with drauga in Zoroastrian thought. That said, there is no explicit contemporary Achaemenid evidence explaining the rationale behind these structures and the forms change from Cambyses to Darius I (Jacobs 2010).
In the last royal inscriptions we possess, those of Artaxerxes II and III, Ahura Mazda is flanked by Mithra and Anahita (A2Sa, A²Sb, A2Sd, A2Ha); in one only Mithra is invoked, though the text is damaged (A²Hb). These inscriptions are mainly found on column bases from Ekbatana and Susa, but the change was clearly not universal: in the foundation inscription A²Hc, for example, Ahura Mazda is given alone in the traditional invocation formula (cf. also the damaged A²Se and A³Pa; Briant 2002, 676f.). This challenging evidence of change in the king's protective deities is a rare example of innovation in Persian royal epigraphy. It is backed up by Berossus' remark (BNJ 680 F11) that Artaxerxes II had an idol of Anahita set up for worship at Babylon and enforced her worship throughout the administrative centres of the empire (cf. Strab. 11.8.4; Briant 2002, 679; Brosius 1998; Waters 2014, 182f.). Finally, at least Mithra persists under Artaxerxes III, for whom we have hardly any inscriptions (A³Pa).
This change has been much debated in scholarship (Boyce 1982, 216-221). The later Achaemenids from Artaxerxes II on can be called Zoroastrians with some justification (Boyce 1982, 263) and it is likewise clear that there was religious change in the 4th century BCE that gradually integrated these two Indo-Iranian deities, the well-established god of covenants and a rather obscure water deity, into 'Zoroastrian' liturgy and royal legitimacy (Plut. Art. 4; Xen. Oec. 4.24; Yasht 5; Boyce 1970; Boyce 1982, 216-221; Boyce/Chaumont/Bier 1989; De Jong 1997, 103-106). Berossus' testimony suggests that like Ahura Mazda, worship of Anahita was intended to unify the Persian imperial elite, as was the expansion of iconic worship. Since the deities change in the most propagandistic genre available to the Achaemenid kings, the inscriptions, the inclusion of Anahita and Mithra was clearly a deliberate political act (Berossus BNJ 680 F11; Briant 2002, 204; Garrison 2011, 17). Deciding whether this change was a top-down imposition as the Greek sources say or a reaction to a bottom-up, local development, however, is complicated by the state of our evidence. It may be a response to changed local sensibilities, especially in Khuzistan, where the epigraphic material is most prominent. If it had a larger audience, as Berossus suggests, it may have been a response to growing, syncretistic cults of Anahita and Mithras, and thus an attempt to bolster dynastic legitimacy with an expanded imperial-level, Iranian cult in the centres of Empire (Briant 2002, 679f.). Finally, but perhaps least likely, it may be no more than a reflection of ongoing religious change within Zoroastrianism, given that the younger Avesta features many deities and Ahura Mazda increasingly loses the dominant role he plays in the older Gathas (Schwartz 1985, 667).
In any case, the reign of Artaxerxes II (404-359 BCE), marked by a very significant calendar reform, in which the names of Zoroastrian deities were substituted for the earlier Persian month-names, by the introduction of the Anahita cult and the worship of Mithra, and by the first mention of Zoroaster in Greek sources, was a turning point in the history of Zoroastrianism (Boyce 1982, ch. 13), elements of which persist today. The impact of Alexander's conquest, the spread of Greek concepts of divinity and worship, and the internal disputes within Zoroastrianism would nonetheless ensure that the history of religion in the areas once controlled by the Achaemenid Empire would remain exceedingly complex in the post-Achaemenid period (Boyce/Grenet/Beck 1991).
The inscriptions do not attest much beyond rather general, core tenets of Zoroastrianism and fail to mention numerous other core features (avoidance of pollution, elementalism, Zoroaster himself, divine personnel etc.). On the other hand, Herodotus' confused account of Persian religion and archaeological remains do attest to some of these missing features, such as spheres of aniconic worship and a concern with elemental purity. While Mary Boyce's and Heidemarie Koch's (1977, 1987) heavily Zoroastrian interpretations of the material are possible at a pinch, the balance of the evidence suggests that the religious world view put forward in the inscriptions may perhaps be best described as 'Mazdaism' in that it clearly lacked ambitions of monotheistic exclusivity and was not yet founded on a canon of texts, concepts and practices. This is shown by the occurrence of other gods in the inscriptions and corroborated by the Persepolis archives (Henkelman 2008). The intent of the religious elements in the inscriptions is to communicate the king's exceptional role in the order of the state and the world, an order that was echoed in his relationship to the gods.
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Henry Heitmann-Gordon & Sebastian Zellner
Henry Heitmann-Gordon & Sebastian Zellner, 'Religious world view', Achaemenid Royal Inscriptions online (ARIo) Project, The ARIo Project, a sub-project of MOCCI, 2020 [http://oracc.museum.upenn.edu/ario/understandingtheinscriptions/religiousworldview/]