Zoroastrianism is the religion and philosophy based on the teachings ascribed to the prophet Zoroaster, after whom the religion is named. The term Zoroastrianism is in general usage, essentially synonymous with Mazdaism, i.e., the worship of Ahura Mazda, exalted by Zoroaster as the supreme divine authority.
Zoroastrianism is uniquely important in the history of religion because of its possible formative links to both Western and Eastern religious traditions. As "the oldest of the revealed credal religions", Zoroastrianism "probably had more influence on mankind directly or indirectly than any other faith". 
The term Zoroastrianism was first attested by the Oxford English Dictionary in 1874 in Archibald Sayce's Principles of Comparative Philology. The first surviving reference to Zoroaster in Western scholarship is attributed to Thomas Browne (1605–1682), who briefly refers to the prophet in his 1643 Religio Medici. The OED records 1743 (Warburton, Pope's Essay) as the earliest reference to Zoroaster. 
The term Mazdaism is a typical 19th century construct, taking Mazda- from the name Ahura Mazda and adding the suffix -ism to suggest a belief system. The March 2001 draft edition of the OED also records an alternate form, Mazdeism, perhaps derived from the French Mazdéisme, which first appeared in 1871. The Zoroastrian name of the religion is Mazdayasna, which combines Mazda- with the Avestan language word yasna, meaning "worship, devotion".
In the English language, an adherent of the faith commonly refers to him- or herself as a Zoroastrian or, less commonly, a Zarathustrian. An older, but still widespread expression is Behdin, meaning "follower of Daena", for which "Good Religion" is one translation. In the Zoroastrian liturgy, the term Behdin is also used as a title for an individual who has been formally inducted into the religion (see navjote for details).
Although older (roughly early first millennium BCE, see Zoroaster), 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. (See Towers of Silence).
Perhaps more importantly, The Histories is a primary source of information on the early period of the Achaemenid era (648–330 BCE), in particular with respect to the role of the Magi. According to Herodotus i.101, the Magi were the sixth tribe of the Medians (until the unification of the Persian empire under Cyrus the Great, all Iranians were referred to as Mede or Mada by the peoples of the Ancient World), who appear to have been the priestly caste of the Mesopotamian-influenced branch of Zoroastrianism today known as Zurvanism, and who wielded considerable influence at the courts of the Median emperors.
Following the unification of the Median and Persian empires in 550 BCE Cyrus II and later his son Cambyses II curtailed the powers of the Magi after they had attempted to seed 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. The "Magi", though persecuted, continued to exist. A year following the death of the first pseudo-Smerdis (named Gaumata), a second pseudo-Smerdis (named Vahyazdāta) attempted a coup. The coup, though initially successful, failed.
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 would later allow Cyrus to free the Jews from captivity and allow them to return to Judea when the emperor took Babylon in 539 BCE. Darius I was certainly a devotee of Ahura Mazda, as attested to several times in the Behistun inscription. But 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, Book of Arda Viraf), many sacred texts were lost when Alexander's troops invaded Persepolis and subsequently destroyed the royal library there. Diodorus Siculus's Bibliotheca historia completed c. 60 BCE, which is to a great extent an encapsulation of earlier works, appears to substantiate Zoroastrian legend (Diod. 17.72.2–17.72.6). According to one archaeological examination, the ruins of the palace of Xerxes bear traces of having been burned (Stolze, 1882). Whether a vast collection of (semi-)religious texts "written on parchment in gold ink", as suggested by the Denkard, actually existed remains a matter of speculation, but is unlikely. Given that many of the Denkards statements-as-fact have since been refuted among scholars, the tale of the library is widely accepted to be fictional. (Kellens, 2002)
When the Sassanid dynasty came into power in 228 CE, they aggressively promoted the Zurvanite form of Zoroastrianism and in some cases persecuted Christians and Manichaeans. When the Sassanids captured territory, they often built fire temples there to promote their religion. 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 Babylon — which had broken with Roman Christianity when the latter condemned Nestorianism — were tolerated and even sometimes favored by the Sassanids. Nestorians lived in large numbers in Mesopotamia and Khuzestan during this period.
A form of Zoroastrianism was apparently also the chief religion of pre-Christian Caucasus region, or at least was prominent there. During periods of Sassanid suzerainty over the Caucasus the Sassanids made attempts to promote the religion there as well.
Well before the 6th century Zoroastrianism had spread to northern China via the Silk Road, gaining official status in a number of Chinese states. Remains of Zoroastrian temples have been found in Kaifeng and Zhenjiang, and according to some scholars, remained as late as the 1130s, but by the 13th century the religion had faded from prominence in China. However, many scholars assert the influence of Zoroastrianism (as well as later Manicheism) on elements of Buddhism, especially in terms of light symbolism.
See also: Persecution of Zoroastrians. In the 7th century, and over the course of at least 16 years (several decades in the case of some provinces), the Sassanid dynasty was overthrown by the Arabs. Although the administration of the state was rapidly Islamicized and subsumed under the Umayyad Caliphate, "there was little serious pressure" exerted on newly-subjected peoples to adopt Islam. Islamic jurists considered only Muslims to be perfectly moral, and "unbelievers might as well be left to their inequities, so long as these did not vex their overlords."
There were also practical considerations: "because of their sheer numbers, the conquered Zoroastrians had to be treated as dhimmis (despite doubts [of the validity of this identification] that persisted down the centuries)," which made them eligible for protection. Thus, in the main, once the conquest was over (with its concordant slaughter, enslavement, looting and destruction) "local terms were agreed on", and the Arab governors protected the local populations in exchange for tribute. The Arabs adopted the Sassanid tax-system, both the land-tax levied on land owners and the poll-tax levied on individuals. The Arabs called this poll-tax jizya, which Muslims were immediately exempted from, and so eventually came to be understood as a tax levied only on non-Muslims (i.e. the dhimmis). In time this poll-tax came to be used as a means to humble the non-Muslims, and a number of laws and restrictions evolved to emphasize the inferior status of them. But under the early orthodox caliphs, as long as the non-Muslims paid their taxes and adhered to the dhimmi laws, administrators were enjoined to leave non-Muslims "in their religion and their land." (Caliph Abu Bakr, qtd. in).
Thus, though subject to a new leadership and harassed, once the horrors of conquest were over, the Zoroastrians were able to continue in their former ways. But there was however a slow but steady social and economic pressure to convert.  The nobility and city-dwellers were the first to convert, with Islam more slowly being accepted among the peasantry and landed gentry. "Power and worldly-advantage" now lay with followers of Islam, and although the "official policy was one of aloof contempt, there were individual Muslims eager to proselytize and ready to use all sorts of means to do so."
And, 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 the fourth caliph Ali and grandson of Islam's prophet Muhammad, had married a captive Sassanid princess named Shahrbanu. This "wholly fictitious figure" was said to have borne Hussain a son, the historical fourth Shi'a caliph, 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. "So, it was no longer the Zoroastrians alone who stood for patriotism and loyalty to the past." The "damning indictment" that becoming Muslim was equivalent to becoming Un-Iranian only remained an idiom in Zoroastrian texts.
With Iranian support (especially Persian support), the Shi'ite Abbasids overthrew the Ummayads in 750, and in the subsequent caliphate government - that nominally lasted until 1258 - Iranians received marked favor (if they were Muslim) in the new government, both in Iran and at the capital in Baghdad. This too 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 directly mainly at Muslim sectarians, it also created a harsher climate for non-Muslims. And 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-10th centuries (excluding copying and lesser amendments, which continue for some time thereafter). All of these works are in Middle Persian (free of Arabic words) dialect of that period, 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 understandable to the laity. Many are these texts are responses to the tribulations of the time, and all of them include exhortations to stand fast in their religious beliefs. Some, such as the Denkard, are doctrinal defenses of the religion, while others are explanations of theological aspects (such as the Bundahishn's) or practical aspects (e.g. explanation of rituals) of it. About sixty such works are known to have existed, of which some are known only from references to them in other works.
Two decrees in particular encouraged the transition to a preponderantly Islamic society. The first edict, adapted from a Arsacid and Sassanid one (but in those to the advantage of Zoroastrians), was that only a Muslim could own Muslim slaves or indentured servants. Thus, a bonded individual owned by a Zoroastrian could automatically become a freeman by converting to Islam. The other edict was that if one male member of a Zoroastrian family were to convert to Islam, he would instantly inherit all its property.
Under Abbasid rule, Muslim Iranians (who by then were in the majority) increasingly found ways to taunt Zoroastrians, and distressing them became a popular sport. For example, in the 9th century, a deeply venerated cypress tree in Khorasan (which Parthian-era legend supposed had been been planted by Zoroaster himself) was felled for the construction of a palace in Baghdad, 2000 miles away. In the 10th century, on the day that a tower of silence had been completed at much trouble and expense, a Muslim official contrived to get up onto it, and to call the adhan (the Muslim call to prayer) from its walls. This was made a pretext to annex the building. Another popular means to distress Zoroastrians was to maltreat dogs, these animals being sacred in Zoroastrianism. Such baiting, which was to continue down the centuries, was indulged in by all; not only by high officials, but by the general uneducated population as well.
But despite these economic and social incentives to convert, Zoroastrianism remained strong in some regions, particularly in those furthest away from the Caliphate capital at Baghdad. In Bukhara (in present-day Uzbekistan), resistance to Islam required the 9th century Arab commander Qutaiba to convert his province four times. The first three times the citizens reverted to their old religion. Finally, the governor made their religion "difficult for them in every way", turned the local fire temple into a mosque, and encouraged the local population to attend Friday prayers by paying each attendee two dirhams. The cities where Arab governors resided were particularly vulnerable to such pressures, and in these cases the Zoroastrians were left with no choice but to either conform or to migrate to regions that had a more amicable administration.
Among these migrations were those to cities in (or on the margins of) the great salt deserts, in particular to Yazd and Kerman, which remain centers of Iranian Zoroastrianism to this day. Yazd became the seat of the Iranian high priests during Mongol Il-Khanate rule, when the "best hope for survival [for a non-Muslim] was to be inconspicuous." Crucial to the present-day survival of Zoroastrianism was a migration from the northeastern Iranian town of "Sanjan in south-western Khorasan", 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" - and who today represent the larger of the two groups of Zoroastrians.
Also in Khorasan in the northeastern Iran, a 10th century Iranian nobleman brought together four Zoroastrian priests to transcribe a Sassanid-era Middle Persian work titled Book of the Lord (Khwaday Namag) from Pahlavi script into Arabic script. This transcription, which remained in Middle Persian prose (an Arabic version, by al-Muqaffa, also exists), was completed in 957 and subsequently became the basis for Firdausi's Book of Kings. It became enormously popular among both Zoroastrians and Muslims alike, and also served to propagate the Sassanid justification for overthrowing the Arsacids (i.e. that the Sassanids had restored the faith to its "orthodox" form after the Hellenistic Arsacids had allowed Zoroastrianism to become corrupt).
The hope for a restoration of a Zoroastrian state (expressed in the 9th century Zoroastrian texts, and in the Shahnameh) declined in the 10th and 11th centuries. By then, local Iranian dynasties, "all vigorously Muslim," had emerged as largely-independent vassals of the Caliphs. In the 16th century, in one of the early letters between Iranian Zoroastrians and their co-religionists in India, the priests of Yazd lamented that "no period [in human history], not even that of Alexander, had been more grievous or troublesome for the faithful than 'this millennium of the demon of Wrath'."
It is believed that key concepts of Zoroastrian eschatology and demonology have had influence on the Abrahamic religions.   On the other hand, Zoroastrianism itself inherited ideas from other belief systems and, like other practiced religions, accommodates some degree of syncretism .
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. However, Zoroastrianism was also strongly affected by the later culture of the Iranian Heroic Age (1500 BCE onwards), an influence that the Indic religions were not subject to. Moreover, the other culture groups that the respective peoples came to interact with were different, for instance in 6th-4th century BCE Western Iran with Fertile Crescent culture, with each side absorbing ideas from the other. Such inter-cultural influences notwithstanding, Zoroastrian scripture is essentially a product of (Indo)Iranian culture, and—representing the oldest and largest corpus pre-Islamic Iranian ideology—is considered a reflection of that culture. Then, 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 characterise 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. The study of pre-Islamic Iran has itself undergone a radical change in direction since the 1950s, and the field is today disinclined to speculation.
Zoroastrianism is often compared with the Manichaeism, which is nominally an Iranian religion but has its origins in the Middle-Eastern Gnosticism. Superficially, such a comparison may be apt as both are uncompromisingly dualistic and Manichaeism nominally adopted many of the Yazatas for its own pantheon. Gherardo Gnoli, in Eliade, Mircea (ed.), The Encyclopaedia of Religion, MacMillan Library Reference USA, New York, 1993, volume 9, page 165, has this to say: "...we can assert that Manichaeism has its roots in the Iranian religious tradition and that its relationship to Mazdaism, or Zoroastrianism, is more or less like that of Christianity to Judaism". As religious types they are however poles apart: Manichaeism equated evil with matter and good with spirit, and was therefore particularly suitable as a doctrinal basis for every form of asceticism and many forms of mysticism. 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.
Many aspects of Zoroastrianism are present in the culture and mythologies of the peoples of the Greater Iran, not least because Zoroastrianism, was a dominant influence on the people of the cultural continent for a thousand years. Even after the rise of Islam and the loss of direct influence, Zoroastrianism remained part of the cultural heritage of the Iranian language-speaking world, in part as festivals and customs, but also because Ferdowsi incorporated a number of the figures and stories from the Avesta in his epic Shāhnāme, which in turn is pivotal to Iranian identity.
See main article: Avesta. The Avesta is the collection of the sacred texts of Zoroastrianism. Although the texts are very old, the compendium as we know it today is essentially the result of a redaction that is thought to have occurred during the reign of Shapur II (309–379 CE). However, some portions of the collection have been lost since then, especially after the fall of the Sassanid empire in 651 CE, after which Zoroastrianism was supplanted by Islam. The oldest existing copy of an Avestan language text dates to 1288 CE.
The most ancient of the texts of the Avesta are in an old or Gathic Avestan. The majority of the texts are however from a later period: most are probably from the Achaemenid era (648–330 BCE), with a few being even younger. All the texts are believed to have been transmitted orally for centuries before they found written form, and in existing copies, the Avestan language words are written in Din dabireh script, a Sassanid era (226–651 CE) invention.
The various texts of the Avesta are generally divided into topical categories, but these are by no means fixed or canonical. Some scholars prefer to place the five categories in two groups, one liturgical and the other general.
The texts of the Avesta are complemented by several secondary works of religious or semi-religious nature, which although not sacred and not used as scripture, have a significant influence on Zoroastrian doctrine. They are all of a much later date — in general from between the 9th and 12th centuries — with the youngest treatises dating to the 17th century. Some of these works quote passages that are believed to be from lost sections of the Avesta.
The most important of these secondary texts (of which there some 60 in all) are:
The use of the expression Zend-Avesta to refer to the Avesta, or the use of Zend as the name of a language or script, are relatively recent and popular mistakes. The word Zend or Zand, meaning "commentary, translation", refers to supplementaries in Middle Persian not intended for use as theological texts by themselves but for religious instruction of the (by then) non-Avestan-speaking public. In contrast, the texts of the Avesta proper remained sacrosanct and continued to be recited in Avestan — which was considered a sacred language.
In a general sense, all the secondary texts mentioned above are also included in the Zend rubric since they too often include commentaries on the Avesta and on the religion.
Ahura Mazda is the beginning and the end, the creator of everything which can and cannot be seen, the Eternal, the Pure and the only Truth. In the Gathas, the most sacred texts of Zoroastrianism thought to have been composed by Zoroaster himself, the prophet acknowledged devotion to no other divinity besides Ahura Mazda.
Daena (din in modern Persian) is the eternal Law, whose order was revealed to humanity through the Mathra-Spenta ("Holy Words"). Daena has been used to mean religion, faith, law, even as a translation for the Hindu and Buddhist term Dharma, often interpreted as "duty" but can also mean social order, right conduct, or virtue. The metaphor of the 'path' of Daena is represented in Zoroastrianism by the muslin undershirt Sudra, the 'Good/Holy Path', and the 72-thread Kushti girdle, the "Pathfinder".
Daena should not be confused with the fundamental principle asha (Vedic rta), the equitable law of the universe, which governed the life of the ancient Indo-Iranians. For these, asha was the course of everything observable, the motion of the planets and astral bodies, the progression of the seasons, the pattern of daily nomadic herdsman life, governed by regular metronomic events such as sunrise and sunset. All physical creation (geti) was thus determined to run according to a master plan — inherent to Ahura Mazda — and violations of the order (druj) were violations against creation, and thus violations against Ahura Mazda. 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, 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).
In this schema of asha versus druj, mortal beings (humans and animals both) play a critical role, for they too are created. Here, in their lives, they are active participants in the conflict and it is their duty to defend order, which would decay without counteraction. Throughout the Gathas, Zoroaster emphasizes deeds and actions, and accordingly 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.
Thus, central to Zoroastrianism is the emphasis on moral choice, to choose between 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 to one another. Reward, punishment, happiness and grief all depend on how individuals live their life.
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.
Through accumulation several other beliefs were introduced to the religion that in some instances supersede those expressed in the Gathas. In the late 19th century the moral and immoral forces came to be represented by Spenta Mainyu and its Satanic antithesis Angra Mainyu, the 'good spirit' and 'evil spirit' emanations of Ahura Mazda respectively. Although the names are old, this opposition is a modern western-influenced development popularized by Martin Haug in the 1880s, and was in effect a realignment of the precepts of Zurvanism (Zurvanite Zoroastrianism), which had invented a third deity, Zurvan, in order to explain a mention of twinship (Yasna 30.3) between the moral and immoral. Although Zurvanism had died out by the 10th century the critical question of the "twin brothers" mentioned in Yasna 30.3 remained, and Haug's explanation provided a convenient defence against Christian missionaries who disparaged the Parsis (Indian Zoroastrians; originally Iranians that migrated to India and retained their Zoroastrian faith) for their 'dualism'. Haug's concept was subsequently disseminated as a Parsi interpretation, thus corroborating Haug's theory and the idea became so popular that it is now almost universally accepted as doctrine.
Achaemenid era (648–330 BCE) Zoroastrianism developed the abstract concepts of heaven, hell, personal and final judgment, all of which are only alluded to in the Gathas. Yasna 19 (which has only survived in a Sassanid era (226–650 CE) Zend commentary on the Ahuna Vairya invocation), prescribes a Path to Judgment known as the Chinvat Peretum or Chinvat bridge (cf: As-Sirāt in Islam), which all souls had to cross, and judgment (over thoughts, words, deeds performed during a lifetime) was passed as they were doing so. 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.
In addition, and strongly influenced by Babylonian and Akkadian practices, the Achaemenids popularized shrines and temples, hitherto alien forms of worship. In the wake of Achaemenid expansion shrines were constructed throughout the empire and particularly influenced the role of Mithra, Aredvi Sura Anahita, Verethregna and Tishtrya, all of which, in addition to their original (proto-)Indo-Iranian functions, now also received Perso-Babylonian functions.
Although the worship of images would eventually fall out of favour (and be replaced by the iconoclastic fire temples), the lasting legacy of the Achaemenids was a vast, complex hierarchy of Yazatas (modern Zoroastrianism's Angels) that were now not just evident in the religion, but firmly established, not least because the divinities received dedications in the Zoroastrian calendar, thus ensuring that they were frequently invoked. Additionally, the Amesha Spenta, the six originally abstract terms that were regarded as direct emanations or aspects or "divine sparks" of Ahura Mazda, came to be personified as an archangel retinue.
Small Zoroastrian communities may be found all over the world, with a continuing concentration in Western India, Central Iran and Southern Pakistan. Zoroastrians of the diaspora are primarily located in Great Britain and the former British colonies — in particular Canada and Australia. Zoroastrian communities comprised two main groups of people: those of South Asian Zoroastrian background, who are known as Parsis (or Parsees), and those of Central Asian background.
See main article: Zoroastrians in Iran.
See main article: Zoroastrianism in Azerbaijan. Communities exist in Tehran, as well as in Yazd, Kerman and Kermanshah, where many still speak an Iranian language distinct from the usual Persian. They call their language Dari (not to be confused with the Dari of Afghanistan). Their language is also called Gabri or Behdinan (literally "Of the Good Religion"). Sometimes their language is named for the cities in which it is spoken, Yazdi or Kermani. Iranian Zoroastrians were historically called Gabrs, originally without a pejorative connotation but in the present-day derogatorily applied to all non-Muslims.
There is some interest among Iranians, as well as people in various Central Asian countries such as Tajikistan and Uzbekistan, in their ancient Zoroastrian heritage; some people in these countries take notice of their Zoroastrian past. At the instigation of the government of Tajikistan, UNESCO declared 2003 a year to celebrate the "3000th anniversary of Zoroastrian culture", with special events throughout the world.
See main article: Parsi people. Following the fall of the Sassanid Empire in 651 many Zoroastrians migrated. Among them were several groups who ventured to Gujarat on the western shores of the Indian subcontinent, where they finally settled. The descendants of those refugees are today known as the Parsis. The year of arrival on the subcontinent cannot be precisely established and Parsi legend and tradition assigns various dates to the event.
In the Indian subcontinent these Zoroastrians enjoyed tolerance and even admiration from other religious communities. From the 19th century onward the Parsis gained a reputation for their education and widespread influence in all aspects of society, partly due to the divisive strategy of British colonialism which favored certain minorities. Parsis are generally more affluent than other Indians and are stereotypically viewed as among the most Anglicised and "Westernised" of the various minority groups. They have also played an instrumental role in the economic development of the region over many decades; several of the best-known business conglomerates of India are run by Parsi-Zoroastrians, including the Tata, Godrej, and Wadia families.
In 2004 the number of Zoroastrians worldwide was estimated at between 124,000 and 190,000. India's 2001 Census found 69,601 Parsi Zoroastrians. In Pakistan they number 5,000, mostly living in Karachi, they have been reinforced in recent years with a number of Zoroastrian refugees from Iran. Anglo America is thought to be home to 18,000–25,000 Zoroastrians of both South Asian and Iranian background. A further 3,500 live in Australia (mainly in Sydney). Iran's figures of Zoroastrians have ranged widely; the last census (1974) before the revolution of 1979 revealed 21,400 Zoroastrians.
Some 10,000 adherents remain in the Central Asian regions that were once considered the traditional stronghold of Zoroastrianism, i.e. Bactria (see also Balkh) which is in Northern Afghanistan, Sogdiana, Margiana and other areas close to Zoroaster's homeland.
In the Indian census of 2001 the Parsis numbered 69,601, representing about 0.006% of the total population of India, with a concentration in and around the city of Mumbai. Due to a low birth rate and high rate of emigration, demographic trends project that by 2020 the Parsis will number only about 23,000 or 0.002% of the total population of India. The Parsis would then cease to be called a community and will be labelled a "tribe". By 2008, the birth-to-death ratio was 1:5 - 200 births per year to 1,000 deaths.
See main article: List of Zoroastrians. Noted Parsis from India include the pioneering Indian industrialist and philanthropist Jamshedji Tata; the industrialist and founder of Indian Civil aviation J. R. D. Tata; Indian political activists Pherozeshah Mehta, Dadabhai Naoroji and Bhikaiji Cama; conductor Zubin Mehta, countertenor Bejun Mehta, composer Kaikhosru Shapurji Sorabji, and rock artist Freddie Mercury (Farrokh Bulsara); British actor and Film Producer Ray Panthaki; nuclear scientist Homi J. Bhabha, the similarly named philosopher Homi K. Bhabha; Field Marshal Sam Manekshaw, author and screenwriter Sooni Taraporevala (of the films Salaam Bombay and Mississippi Masala), authors Rohinton Mistry and Firdaus Kanga. Parsis famed for their philanthropy include Jamsetjee Jeejebhoy and the eponymous Cowasji Jehangir Readymoney, both of whom were knighted for their munificence. The Indian industrial families Tata family, Godrej family and Wadia family are also of Parsi Zoroastrian background. Noted members of the more recently arrived Irani community include Bollywood director Ardeshir Irani and cricketer Ronnie Irani. Noted Pakistani Parsis include Ardeshir Cowasjee, a renowned writer and editor for The Dawn newspaper of Pakistan, founded and established by that country's founding father, Mohammed Ali Jinnah whose wife was a Parsi, as well as writer Bapsi Sidhwa and Byram Avari of the Avari family involved in the service industry.
Merwan Sherier Irani (1894 to 1969) known as Meher Baba by his devotees, an Indian religious leader from the 20th century often cited his Zoroastrian beliefs.
Noted Iranian Zoroastrians include Dr. Farhang Mehr, former deputy prime minister of Iran, Boston University professor emeritus, longtime activist for religious freedom, and subject of the biography "Triumph Over Discrimination" by Lylah M. Alphonse.
Notable converts to Zoroastrianism include Swedish artist and author Alexander Bard.