In Zurvanism, Zurvan is the hypostasis of Time (and Space). The name, as it appears in Middle Persian, derives from Avestan zruvan-, 'time', with the same range of meaning as in the English language. The name "Zurvan", like 'time', also appears in other belief systems, but in those religions are only nominally related to the Zurvan of Zurvanism.
Although the details of the origin and development of Zurvanism remain murky (for a summary of the three opposing opinions, see Ascent and acceptance below), it is generally accepted that Zurvanism was a branch of greater Zoroastrianism (Boyce 1957:157-304); that the doctrine of Zurvan was a sacerdotal response to resolve a perceived inconsistency in the sacred texts (Zaehner, 1955, intro; See development of the "twin brother" doctrine below); and that this doctrine was probably introduced during the second half of the Achaemenid era (Henning, 1951; loc. Cit. Boyce 1957:157-304).
Zurvanism enjoyed royal sanction during the Sassanid era (226-651 CE) but no traces of it remain beyond the 10th century. Although Sassanid era Zurvanism was certainly influenced by Hellenic philosophy, whether Zoroastrian Zurvan was an adaptation of an antecedent or alien divinity of Time has not been conclusively established.
Non-Zoroastrian accounts of typically Zurvanite beliefs were the first traces of Zoroastrianism to reach the west, which misled European scholars to conclude that Zoroastrianism was a monist faith.
Most of what is known of Zurvanism during the Sassanid period is from contemporaneous Christian Armenian and Syriac sources. The Kartir inscription at Ka'ba-i Zartosht and the edict of Mihr-Narse are the only contemporaneous native sources that reveal anything about Zurvanism, the latter being the only native evidence from that period that is frankly Zurvanite. The few other Persian language commentaries on the religion of the Sassanid period were all composed after the fall of the empire.
While the Armenian and Syriac sources depict the religion of the Sassanids as having been distinctly Zurvanite, the later native commentaries are primarily Mazdean and with only one exception (10th c. Denkard 9.30) do not mention Zurvan at all. Of the remaining so-called Pahlavi texts only two, the Mēnōg-i Khrad and the "Selections of Zatspram" (both 9th c.) reveal a Zurvanite tendency. The latter is considered to be the latest Zoroastrian text that provides any evidence of the cult of Zurvan. The foreign accounts of the Zurvanite father-of-twins doctrine is substantiated by only a single Persian language source, the Ulema-i Islam ("Doctors of Islam", 13th c.), that, notwithstanding the title, is evidently by a Zoroastrian.
There is no hint of any worship of Zurvan in any of the texts of the Avesta, even though the texts (as they exist today) are the result of a Sassanid era redaction. Zaehner proposes that this is because the individual Sassanid monarchs were not always Zurvanite and that Mazdean Zoroastrianism just happened to have the upper hand during the crucial period that the canon was finally written down (Zaehner, 1955:48; Duchesne-Guillemin, 1956:108). In the texts composed prior to the Sassanid period, Zurvan appears twice, as both an abstract concept and as a minor divinity, but there is no evidence of a cult. In Yasna 72.10 Zurvan is invoked in the company of Space and Air (Vata-Vayu) and in Yasht 13.56, the plants grow in the manner Time has ordained according to the will of Ahura Mazda and the Amesha Spentas. Two other references to Zurvan are also present in the Vendidad, but although these are late additions to the canon, they again do not establish any evidence of a cult. Zurvan does not appear in any listing of the Yazatas (Dhalla, 1932).
Certain however is that by the Sassanid era (226–651 CE), the divinity "Infinite Time" was well established and enjoyed royal patronage. It was during the reign of Sassanid Emperor Shapur I (241-272) that Zurvanism appears to have developed as a cult and it was presumably in this period that Greek and Indic concepts were introduced to Zurvanite Zoroastrianism.
It is however not known whether Sassanid era Zurvanism and Mazdaism were separate sects, each with their own organization and priesthood, or simply two tendencies within the same body. That Mazdaism and Zurvanism competed for attention can been inferred from the works of Christian and Manichean polemicists, but the doctrinal incompatibilities were not so extreme "that they could not be reconciled under the broad aegis of an imperial church" (Boyce, 1957:308).
Following the fall of the Sassanid Empire in the 7th century, Zoroastrianism was gradually supplanted by Islam. The former continued to exist but in an increasingly decimated state and the remaining Zoroastrians appear to have gradually returned to the Mazdean doctrine prescribed by Zoroaster in the Gathas (see also legacy, below). By the 10th century, Zurvanism had ceased to exist, leaving Mazdaism the sole remaining form of Zoroastrianism.
Why the cult of Zurvan vanished (while Mazdaism did not) remains again an issue of scholarly debate. Arthur Christensen, one of the first proponents of the theory that Zurvanism was the state religion of the Sassanids, suggested that the rejection of Zurvanism in the post-conquest epoch was a response and reaction to the new authority of Islamic monotheism that brought about a deliberate reform of Zoroastrianism that aimed to establish a stronger orthodoxy (Boyce, 1957:305). Zaehner is of the opinion that the Zurvanite priesthood had a "strict orthodoxy which few could tolerate. Moreover, they interpreted the Prophet's message so dualistically that their God was made to appear very much less than all-powerful and all-wise. Reasonable as so absolute a dualism might appear from a purely intellectual point of view, it had neither the appeal of a real monotheism nor had it any mystical element with which to nourish its inner life." (Zaehner, 1961)
Another possible explanation postulated by Boyce (1957:308-309) is that Mazdaism and Zurvanism were divided regionally, that is, with Mazdaism being the predominant tendency in the regions to the north and east (Bactria, Margiana, and other satrapies closest to Zoroaster's homeland), while Zurvanism was prominent in regions to the south and west (closer to Babylonian and Greek influence). This is supported by Manichean evidence that indicates that 3rd century Mazdean Zoroastrianism had its stronghold in Parthia, to the northeast. Following the fall of the Persian Empire, the south and west were relatively quickly assimilated under the banner of Islam, while the north and east remained independent for some time before these regions too were absorbed. (Boyce, 1957:308-309). This could also explain why Armenian/Syriac observations reveal a distinctly Zurvanite Zoroastrianism, and inversely, could explain the strong Greek and Babylonian influence on Zurvanism (see types of Zurvanism, below).
As the priesthood sought to explain it, if the Malevolent Spirit (lit: Angra Mainyu) and the Benevolent Spirit (Spenta Mainyu, identified with Ahura Mazda) were twins, then they must have had a "father", who must have existed before them. The priesthood settled on Zurvan - the hypostasis of (Infinite) Time - as being "the only possible 'Absolute' from whom the twins could proceed" and which was the source of good in the one and the source of evil in the other (Zaehner, 1961).
The Zurvanite "twin brother" doctrine is also evident in Zurvanism's cosmogonical creation myth, that in its "classic" form, does not contradict the Mazdean model of the origin and evolution of the universe, which begins where the Zurvanite model ends. It may well be (as proposed by Cumont and Schaeder) that the Zurvanite cosmogony was an adaptation of an antecedent Hellenic Chronos cosmogony that portrayed Infinite Time as the "Father of Time" (not to be confused with Cronus, a Titan and father of Zeus) who the Greeks equated with Oromasdes, i.e. Ohrmuzd/Ahura Mazda.
The "classic" Zurvanite model of creation, preserved only by non-Zoroastrian sources, proceeds as follows: In the beginning, the great God Zurvan existed alone. Desiring offspring that would create 'heaven and hell and everything in between,' Zurvan sacrificed for a thousand years. Towards the end of this period, androgyne Zurvan began to doubt the efficacy of sacrifice and in the moment of this doubt Ohrmuzd and Ahriman were conceived: Ohrmuzd for the sacrifice and Ahriman for the doubt. Upon realizing that twins were to be born, Zurvan resolved to grant the first-born sovereignty over creation. Ohrmuzd perceived Zurvan's decision, which He then communicated to His brother. Ahriman then preempted Ohrmuzd by ripping open the womb to emerge first. Reminded of the resolution to grant Ahriman sovereignty, Zurvan conceded, but limited kingship to a period of 9000 years, after which Ohrmuzd would rule for all eternity (Zaehner, 1955:419-428).
Christian and Manichean missionaries considered this doctrine to be exemplary of the Zoroastrian faith and it was these and similar texts that first reached the west. Corroborated by Anquetil-Duperron's "erroneous rendering" of Vendidad 19.9, these led to the late 18th century conclusion that Infinite Time was the first Principle of Zoroastrianism and Ohrmuzd was therefore only "the derivative and secondary character." Ironically, the fact that no Zoroastrian texts contained any hint of the born-of-Zurvan doctrine was considered to be evidence of a latter-day corruption of the original principles. The opinion that Zoroastrianism was so severely dualistic that it was, in fact, ditheistic or even tritheistic would be widely held until the late 1800s (Dhalla, 1932:490-492; cf. Boyce, 2002:687).
According to Duchesne-Guillemin, this division is "redolent of Gnosticism or – still better – of Indian cosmology." The parallels between Zurvan and Prajapati of Rig Veda 10.129 had been taken by Widengren to be evidence of a proto-Indo-Iranian Zurvan, but these arguments have since been dismissed (Duchesne-Guillemin, 1956). Nonetheless, there is a semblance of Zurvanite elements in Vedic texts, and as Zaehner puts it "Time, for the Indians, is the raw material, the material prima of all contingent being."
While Zoroaster's Ormuzd created the universe with his thought, materialist Zurvanism challenged the concept that anything could be made out of nothing. This was a patently alien idea, discarding core Zoroastrian tenets in favor of the position that the spiritual world (including heaven and hell, reward and punishment) did not exist.
While the fundamental division of the material and spiritual was not altogether foreign to the Avesta (Geti and Mainyu, middle Persian: menog, are terms in Mazdaist tradition, where Ahura Mazda is said to have created all first in its spiritual, then later in its material form), the material Zurvanites redefined menog to suit Aristotelian principles to mean that which did not (yet) have matter, or alternatively, that which was still the unformed primal matter. Even this is not necessarily a violation of orthodox Zoroastrian tradition since the divinity Vayu is present in the middle space between Ormuzd and Ahriman, the void separating the kingdoms of light and darkness.
From the point of view of modern Zoroastrianism (which is today synonymous with Mazdaism), the cult of Zurvan is a dilemma that many would wish didn't exist. While the cult of Zurvan has no legacy that could not have reached modern Zoroastrianism by other means, the sheer force of Zurvanism's overt dualism still finds an echo in western scholarship. The incompatibility of Zurvanite dualism with the strongly monotheistic modern Zoroastrianism has left present-day Zoroastrians with the option of either ignoring that Zurvanism ever existed or that its precepts were downright heretical.
One such sacrilege is considered to be the Zurvanite interpretation of Yasna 30.3-5, which gives Zurvanism its "twin brother" (born of Zurvan) doctrine. It revokes Zoroaster's own characterization of Ahura Mazda as the one uncreated God (Yasna 45.2) and the omniscient Creator of all (Yasna 44.7). Zoroaster's doctrine of an uncreated God is also evident in Yasna 30.3, in the same passage that is the exogenesis of the "twin brother" principle.
The pessimism evident in Zurvanite fatalism is a stark contradiction of essentially optimistic Mazdaism and is a direct violation of what is perhaps Zoroaster's greatest contribution to religious philosophy: the concept of a free will. In Yasna 45.9, Ahura Mazda "has left to men's wills" to choose between doing good and doing evil. By leaving destiny in the hands of fate, the cult of Zurvan distanced itself from the most sacred of Zoroastrian tenets: that of the efficacy of good thoughts, good words and good deeds.
That the Zurvanite view of creation was an apostasy even for medieval Zoroastrians is apparent from the 10th century Denkard, which in a commentary on Yasna 30.3-5 turns what the Zurvanites considered the words of the prophet into Zoroaster recalling "a proclamation of the Demon of Envy to mankind that Ohrmuzd and Ahriman were two in one womb." (Denkard 9.30.4). Zaehner considers this passage of the Denkard to be an ingenious misinterpretation of Yasna 30.
That Zurvanism is altogether considered the heresy is however remarkable since the strict dualism that was implicit to the cult was more in line with the dualism alluded to in Zoroaster's own Gathas than with the polytheistic rationalizations of natural phenomena that Zoroastrianism had almost become by the end of the Achaemenid period. The fundamental goal of "classical Zurvanism" to bring the doctrine of the "twin spirits" in accord with what was otherwise understood of Zoroaster's teaching may have been excessive, but (according to Zaehner) it was not altogether misguided. In noting the emergence of an overtly dualistic doctrine during the Sassanid period, Zaehner (1961) asserted that
Thus, - according to Zaehner - while the direction that the Sassanids took was not altogether at odds with the spirit of the Gathas, the extreme dualism that accompanied a divinity that was remote and inaccessible made the faith less than attractive. Zurvanism was then truly heretical only in the sense that it weakened the appeal of Zoroastrianism.
Nonetheless, that Zurvanism was the predominant brand of Zoroastrianism during the cataclysmic years just prior to the fall of the empire, is, according to Duchesne-Guillemin, evident in the degree of influence that Zurvanism (but not Mazdaism) would have on the Iranian brand of Shi'a Islam. Writing in the historical present, he notes that "under Chosrau II (r. 590-628) and his successors, all kinds of superstitions tend to overwhelm the Mazdean religion, which gradually disintegrates, thus preparing the triumph of Islam." Thus, "what will survive in popular conscience under the Muslim varnish is not Mazdeism: it is Zervanite fatalism, well attested in Persian literature" (Duchesne-Guillemin, 1956:109). This is also a thought expressed by Zaehner, who observes that Ferdowsi, in his Shahnameh, "expounds views which seem to be an epitome of popular Zervanite doctrine" (Zaehner, 1955:241). Thus, according to Zaehner and Duchesne-Guillemin, Zurvanism's pessimistic fatalism was a formative influence on the Iranian psyche, paving the way (as it were) for the rapid adoption of Shi'a philosophy during the Safavid era.
According to Zaehner and Shaki, in Middle Persian texts of the 9th century, Dahri (from Ar.-Persian dahr, time, eternity) is the appellative term for adherents of the Zurvanite doctrine that the universe derived from Infinite Time. The later Persian and Arabic literature, the term would come to be a derogatory term for 'atheist' or 'materialist'. The term also appears - in conjunction with other terms for skeptics – in Denkard 3.225 and in the Skand-gumanig wizar where "one who says god is not, who are called dahari, and consider themselves to be delivered from religious discipline and the toil of performing meritorious deeds" (Shaki, 2002:587-588).