Mazda is not immanent in the world, and His creation is represented by the Amesha Spentas and the host of other Yazatas, through whom the works of God are evident to humanity, and through whom worship of Mazda is ultimately directed.

The political power of the pre-Islamic Iranian dynasties lent Zoroastrianism immense prestige in ancient times, and some of its leading doctrines were adopted by other religious systems. It has no major theological divisions (the only significant schism is based on calendar differences), but it is not uniform.

Zoroastrians believe that there is one universal and transcendent God, Ahura Mazda. He is said to be the one uncreated Creator to whom all worship is ultimately directed.[6] Ahura Mazda's creation—evident as asha, truth and order—is the antithesis of chaos, which is evident as druj, falsehood and disorder. The resulting conflict involves the entire universe, including humanity, which has an active role to play in the conflict.[6]

The religion states that active participation in life through good thoughts, good words, and good deeds is necessary to ensure happiness and to keep chaos at bay. This active participation is a central element in Zoroaster's concept of free will,

Ahura Mazda will ultimately prevail over the evil Angra Mainyu or Ahriman, at which point the universe will undergo a cosmic renovation and time will end. In the final renovation, all of creation—even the souls of the dead that were initially banished to "darkness"—will be reunited in Ahura Mazda, returning to life in the undead form. At the end of time, a savior-figure (a Saoshyant) will bring about a final renovation of the world (frasho.kereti), in which the dead will be revived.[6]

While the Iranian authorities do not permit proselytizing within Iran, Iranian Zoroastrians in exile have actively encouraged missionary activities, with The Zarathushtrian Assembly in Los Angeles and the International Zoroastrian Centre in Paris as two prominent centres.

In Zoroastrian tradition, life is a temporary state in which a mortal is expected to actively participate in the continuing battle between truth and falsehood.

On the fourth day after death, the soul is reunited with its fravashi, in which the experiences of life in the material world are collected for the continuing battle in the spiritual world.

Zoroastrianism emerged out of a common prehistoric Indo-Iranian religious system dating back to the early 2nd millennium BCE.[9] According to Zoroastrian tradition, Zoroaster was a reformer who exalted the deity of Wisdom, Ahura Mazda, to the status of Supreme Being and Creator, while demoting various other deities and rejecting certain rituals.

Although older, Zoroastrianism only enters recorded history in the mid-5th century BCE. Herodotus' The Histories (completed c. 440 BCE) includes a description of Greater Iranian society with what may be recognizably Zoroastrian features, including exposure of the dead.

Following the unification of the Median and Persian empires in 550 BCE, Cyrus the Great and, later, his son Cambyses II curtailed the powers of the Magi after they had attempted to sow dissent following their loss of influence. In 522 BCE, the Magi revolted and set up a rival claimant to the throne. The usurper, pretending to be Cyrus' younger son Smerdis, took power shortly thereafter. Owing to the despotic rule of Cambyses and his long absence in Egypt, "the whole people, Persians, Medes and all the other nations" acknowledged the usurper, especially as he granted a remission of taxes for three years (Herodotus iii. 68).

According to the Behistun Inscription, pseudo-Smerdis ruled for seven months before being overthrown by Darius I in 521 BCE.

Whether Cyrus II was a Zoroastrian is subject to debate. It did, however, influence him to the extent that it became the non-imposing religion of his empire, and its beliefs later allowed Cyrus to free the Jews and allow them to return to Judea when the emperor took Babylon in 539 BCE. Darius I was a devotee of Ahura Mazda, as attested to several times in the Behistun inscription. However, whether he was a follower of Zoroaster has not been conclusively established, since devotion to Ahura Mazda was (at the time) not necessarily an indication of an adherence to Zoroaster's teaching. Darius I and later Achaemenid emperors, though acknowledging their devotion to Ahura Mazda in inscriptions, appear to have permitted religions to coexist. Nonetheless, it was during the Achaemenid period that Zoroastrianism gained momentum. A number of the Zoroastrian texts that today are part of the greater compendium of the Avesta have been attributed to that period. It was also during the later Achaemenid era that many of the divinities and divine concepts of proto-Indo-Iranian religion(s) were incorporated in Zoroastrianism, in particular those to whom the days of the month of the Zoroastrian calendar are dedicated. This calendar is still used today, a fact that is attributed to the Achaemenid period. Additionally, the divinities, or yazatas, are present-day Zoroastrian angels (Dhalla, 1938). Almost nothing is known of the status of Zoroastrianism under the Seleucids and Parthians, who ruled over Persia following Alexander the Great's invasion in 330 BCE. According to later Zoroastrian legend (Denkard and the Book of Arda Viraf), many sacred texts were lost when Alexander's troops invaded Persepolis and subsequently destroyed the royal library there.

When the Sassanid dynasty came into power in 228 CE, they aggressively promoted the Zurvanite form of Zoroastrianism and, in some cases, persecuted Christians.[10] When the Sassanids captured territory, they often built fire temples there to promote their religion. After Constantine, the Sassanids were suspicious of Christians, not least because of their perceived ties to the Christian Roman Empire. Thus, those Christians loyal to the Patriarchate of the Church of the East—which broke with Roman Christianity in the Nestorian schism—were tolerated and even sometimes favored by the Sassanids. A form of Zoroastrianism was also prominent in the pre-Christian Caucasus region (especially modern-day Azerbaijan). During the periods of their suzerainty over the Caucasus, the Sassanids made attempts to promote the religion there as well. Well before the 6th century CE, Zoroastrianism had spread to northern China via the Silk Road, gaining official status in a number of Chinese states.[citation needed] Remains of Zoroastrian temples have been found in Kaifeng and Zhenjiang. By the 13th century, the religion had faded from prominence in China. However, Zoroastrianism (as well as later Manicheism) may still have influenced elements of Buddhism, especially in terms of light symbolism.

In time, a tradition evolved by which Islam was made to appear as a partly Iranian religion. One example of this was a legend that Husayn, son the fourth caliph Ali and grandson of Islam's prophet Muhammad, had married a captive Sassanid princess named Shahrbanu. This "wholly fictitious figure"[17] was said to have borne Husayn a son, the historical fourth Shi'a imam, who claimed that the caliphate rightly belonged to him and his descendants, and that the Umayyads had wrongfully wrested it from him. The alleged descent from the Sassanid house counterbalanced the Arab nationalism of the Umayyads, and the Iranian national association with a Zoroastrian past was disarmed. Thus, according to scholar Mary Boyce, "it was no longer the Zoroastrians alone who stood for patriotism and loyalty to the past."[17] The "damning indictment" that becoming Muslim was equivalent to becoming Un-Iranian only remained an idiom in Zoroastrian texts.[17] With Iranian (especially Persian) support, the Abbasids overthrew the Ummayads in 750, and in the subsequent caliphate government—that nominally lasted until 1258—Muslim Iranians received marked favor in the new government, both in Iran and at the capital in Baghdad. This mitigated the antagonism between Arabs and Iranians, but sharpened the distinction between Muslims and non-Muslims. The Abbasids zealously persecuted heretics, and although this was directed mainly at Muslim sectarians, it also created a harsher climate for non-Muslims.[18] Although the Abbasids were deadly foes of Zoroastrianism, the brand of Islam they propagated throughout Iran became in turn ever more "Zoroastrianized", making it easier for Iranians to embrace Islam. The 9th century was the last in which Zoroastrians had the means to engage in creative work on a great scale, and the 9th century has come to define the great number of Zoroastrian texts that were composed or re-written during the 8th to 10th centuries (excluding copying and lesser amendments, which continue for some time thereafter). All of these works are in the Middle Persian dialect of that period (free of Arabic words), and written in the difficult Pahlavi script (hence the adoption of the term "Pahlavi" as the name of the variant of the language, and of the genre, of those Zoroastrian books). If read aloud, these books would still have been intelligible to the laity. Many of these texts are responses to the tribulations of the time, and all of them include exhortations to stand fast in their religious beliefs.

Another popular means to distress Zoroastrians was to maltreat dogs, as these animals are sacred in Zoroastrianism.

Crucial to the present-day survival of Zoroastrianism was a migration from the northeastern Iranian town of "Sanjan in south-western Khorasan",[21] to Gujarat, in western India. The descendants of that group are today known as the Parsis—"as the Gujaratis, from long tradition, called anyone from Iran"[21]—who today represent the larger of the two groups of Zoroastrians.

It is believed that key concepts of Zoroastrian eschatology and demonology have had influence on the Abrahamic religions.[25][26] On the other hand, Zoroastrianism itself inherited ideas from other belief systems and, like other "practiced" religions, accommodates some degree of syncretism.[27]

Many traits of Zoroastrianism can be traced back to the culture and beliefs of the prehistorical Indo-Iranian period, that is, to the time before the migrations that led to the Indians and Iranians becoming distinct peoples. Zoroastrianism consequently shares elements with the historical Vedic religion that also has its origins in that era.

They are therefore thought to have descended from a common Proto-Indo-Iranian religion. However, Zoroastrianism was also strongly affected by the later culture of the Iranian Heroic Age (1500 BCE onwards), an influence to which the Indic religions were not subject.

together with the Vedas, which represent the oldest texts of the Indian branch of Indo-Iranian culture, it is possible to reconstruct some facets of prototypical Indo-Iranian beliefs. Since these two groups of sources also represent the oldest non-fragmentary evidence of Indo-European languages, the analysis of them also motivated attempts to characterize an even earlier Proto-Indo-European religion, and in turn influenced various unifying hypotheses like those of Carl Gustav Jung or James George Frazer. Although these unifying notions deeply influenced the modernists of the late 19th and early 20th century, they have not fared well under the scrutiny of more recent interdisciplinary peer review.

Zoroastrianism, on the other hand, rejects every form of asceticism, has no dualism of matter and spirit (only of good and evil), and sees the spiritual world as not very different from the natural one, and the word "paradise" (via Latin and Greek from Avestan pairi.daeza, literally "stone-bounded enclosure") applies equally to both. Manichaeism's basic doctrine was that the world and all corporeal bodies were constructed from the substance of Satan, an idea that is fundamentally at odds with the Zoroastrian notion of a world that was created by God and that is all good, and any corruption of it is an effect of the bad. From what may be inferred from many Manichean texts and a few Zoroastrian sources, the adherents of the two religions (or at least their respective priesthoods) despised each other intensely.

Zoroastrianism is a tradition that has nourished and sustained the lives of its adherents for countless generations. It combines cosmogonic dualism and escathological monotheism in a manner unique to itself among the religions of the world. Zoroastrianism proclaims a movement through time from dualism to monotheism.[30]

Zoroastrianism was founded by the Prophet Zoroaster (or Zarathustra) in ancient Iran. However, it is debated to exactly when he lived, as estimates range from 1700 BCE[32] to 500 BCE.[33] The precise date of the founding of Zoroastrianism is uncertain. An approximate date of 1500–1200 BCE has been established through archaeological evidence and linguistic comparisons with the Hindu text, the Rig Veda. However there is no way of knowing exactly when Zoroaster lived, as he lived in what, to his people, were prehistoric times.[34]

Zoroaster's birth and early life are little documented. What is known is recorded in the Gathas—the core of the Avesta, which contains hymns thought to be composed by Zoroaster himself.

This vision radically transformed his view of the world, and he tried to teach this view to others. Zoroaster believed in one creator God, teaching that only one God was worthy of worship.

Zoroaster taught against over-ritualising religious ceremonies.

Zoroaster died in his late 70s.

This concept of asha versus the druj should not be confused with the good-versus-evil battle evident in western religions, for although both forms of opposition express moral conflict, the asha versus druj concept is more systemic and less personal, representing, for instance, chaos (that opposes order); or "uncreation", evident as natural decay (that opposes creation); or more simply "the lie" (that opposes truth and righteousness). Moreover, in his role as the one uncreated creator of all, Ahura Mazda is not the creator of druj, which is "nothing", anti-creation, and thus (likewise) uncreated. Thus, in Zoroaster's revelation, Ahura Mazda was perceived to be the creator of only the good (Yasna 31.4), the "supreme benevolent providence" (Yasna 43.11), that will ultimately triumph (Yasna 48.1).

asceticism is frowned upon in Zoroastrianism. In later Zoroastrianism, this was explained as fleeing from the experiences of life, which was the very purpose that the urvan (most commonly translated as the "soul") was sent into the mortal world to collect.

The avoidance of any aspect of life, which includes the avoidance of the pleasures of life, is a shirking of the responsibility and duty to oneself, one's urvan, and one's family and social obligations.

Central to Zoroastrianism is the emphasis on moral choice, to choose the responsibility and duty for which one is in the mortal world, or to give up this duty and so facilitate the work of druj. Similarly, predestination is rejected in Zoroastrian teaching. Humans bear responsibility for all situations they are in, and in the way they act toward one another. Reward, punishment, happiness, and grief all depend on how individuals live their lives.[38] In Zoroastrianism, good transpires for those who do righteous deeds. Those who do evil have themselves to blame for their ruin. Zoroastrian morality is then to be summed up in the simple phrase, "good thoughts, good words, good deeds" (Humata, Hukhta, Hvarshta in Avestan), for it is through these that asha is maintained and druj is kept in check.

Achaemenid era (648–330 BCE) Zoroastrianism developed the abstract concepts of heaven and hell, as well as personal and final judgment, all of which are only alluded to in the Gathas.

However, the Zoroastrian personal judgment is not final. At the end of time, when evil is finally defeated, all souls will be ultimately reunited with their Fravashi. Thus, Zoroastrianism can be said to be a universalist religion with respect to salvation.

Ahura Mazda first created seven abstract heavenly beings called Amesha Spentas, who support him and represent beneficent aspects, along with numerous yazads, lesser beings worthy of worship. He then created the universe itself in order to ensnare evil. Ahura Mazda created the floating, egg-shaped universe in two parts: first the spiritual (menog) and 3,000 years later, the physical (getig). Ahura Mazda then created Gayomard, the archetypical perfect man, and the first bull.[38]

While Ahura Mazda created the universe and mankind, Angra Mainyu, whose instinct is to destroy, miscreated demons, evil yazads, and noxious creatures (khrafstar) such as snakes, ants, and flies. Angra Mainyu created an opposite, evil being for each good being, except for humans, which he found he could not match. Angra Mainyu invaded the universe through the base of the sky, inflicting Gayomard and the bull with suffering and death. However, the evil forces were trapped in the universe and could not retreat.

Zoroastrianism also includes beliefs about the renovation of the world and individual judgment (cf. general and particular judgment), including the resurrection of the dead.

Zoroastrian hell is reformative; punishments fit the crimes, and souls do not rest in eternal damnation. Hell contains foul smells and evil food, and souls are packed tightly together although they believe they are in total isolation.[38] In Zoroastrian eschatology, a 3,000-year struggle between good and evil will be fought, punctuated by evil's final assault. During the final assault, the sun and moon will darken and mankind will lose its reverence for religion, family, and elders. The world will fall into winter, and Angra Mainyu's most fearsome miscreant, Azi Dahaka, will break free and terrorize the world.[38] The final savior of the world, Saoshyant, will be born to a virgin impregnated by the seed of Zoroaster while bathing in a lake. Saoshyant will raise the dead – including those in both heaven and hell – for final judgment, returning the wicked to hell to be purged of bodily sin. Next, all will wade through a river of molten metal in which the righteous will not burn. Heavenly forces will ultimately triumph over evil, rendering it forever impotent. Saoshyant and Ahura Mazda will offer a bull as a final sacrifice for all time, and all men will become immortal. Mountains will again flatten and valleys will rise; heaven will descend to the moon, and the earth will rise to meet them both.[38]