It is, however, appropriate to re-establish the historical facts in their tragic and cruel reality.
The Mazdaean minorities which were not sided with Khorassan for organizing resistance to the invader withdrew into closed communities. For some centuries they were able to maintain a clandestine activity in the rural districts. Whilst certain fire-temples discreetly kept to their worship, it was in Fars province that the theologians preserved their religious knowledge in the Pahlavi writings. Being faced with the majority establishment of the Islamic faith and to forestall massive conversions, this resurgence of the Mazdaean religious culture culminated in the 8th and 9th centuries (2nd and 3rd of the Hegira). It was, nevertheless, soon followed by a massive exodus of Zoroastrians who, refusing conversion or the status and capitation (jizya) of infidels (dhimmi), fled towards Gujarat (8th/10th centuries) where they founded the Parsi colonies of India.
At the same period a nostalgic new literature of ancient Mazdaean Iran arose in the Iranian east, an intellectual step marked by Firdausi’s incomparable Shah Namah.
But the Arab authors and historians manifestly wished to ignore the culture of ancient Mazdaean Iran whose riches were appropriated by Islam in crushing the Sassanian empire. It suffices to mention the names of scholars, astronomers, mathematicians, doctors and philosophers of origin, to ascertain that the whole of the intellectual prestige of early Islamic civilization came from Iran, through the direct cultural borrowing of the Muslim occupier from the Mazdaean occupied, and by the inclinations of new dynasties favourable to Mazdaean thought, like the Barmacids who contributed to the accession to power of the Abbasids, the Samanids and the Buyids.
If early medieval Islam transmitted this cultural heritage to the west, with the collapse of the Musulman empire divided and weakened since the 8th century, and after repeated blows of the Mongols and the Crusades, Islamic decadence followed the end of Persian influence (Baghdad 1258-1401) and was to darken into obscurantism.
But from the beginnings of Islam in Iran (at Kufa and Basra), it was Manichaeism, much tended to be eclipsed because it no longer existed, which had played the role of catalyst between Iranian thinking and Islamic dogmas — in particular with the notions of “spiritual light”, “column of light”, “light of Mahomet”, etc. 
One cannot follow in their isolated developments the Muslim authors who had striven to recoup some religious concepts from ancient Persia into Iranian Islam, and to pass over in silence the sufferings of the Mazdaean folk crushed by centuries of physical and doctrinal occupation, to the gain of a Persian esoterism which had borrowed from the Zoroastrians whatever had made it great. With the help of Sufi syncretism, Ismaili gnosis and certain theological schools (Isfahan), enriched by neo-Platonism, elaborated a Shi’ite theosophy peculiarly tinged with Manichaean and Mazdaeo-Zoroastrian ideas. The concept of the Khvarenah. inspired the Ismaili A. Y. Sejestani (10th century), then above all the theosophy of Light of the 12th century S. Y. Sohrawardi, called the “Shaikh al-Ishraq”, and the “oriental theosophies” (Ishraqiyun) which followed until the philosophical school of Molla Sadra Shirazi (17th century).
These closed circles claimed to “restore” within an Islamic milieu the ancient Zoroastrian wisdom ever represented by the Zardushtis of Iran and the Parsis of India who ignored these minority syncretic ventures .
Henry Corbin, a French specialist in Islamism and the religions of Arabia, had devoted an important part of his studies to Persian Islam in which he accords, after the German Max Horten  a particular and remarkable role to Shihaboddin Yahya Sohrawardi (1155-1191), in fact a role truly overestimated by the French scholar.
Sohrawardi had well concealed the Avestic origin of his borrowings, it remaining no less true that he could not “resuscitate” a religion to which he did not belong and whose followers still exist, not solely under the Muslim occupation of Iran, but also in India. Noting the inevitable misunderstanding H. Corbin did not for all that, linger over the Zoroastrians in Iran or in exile, and still continued to call Sohrawardi the “resurrector of the wisdom of ancient Persia” or of the “Zoroastrian theosophy of ancient Persia” .
In this respect, it is most surprising to read that Sohrawardi, the “shaikh al-Ishraq” himself explains in commenting on the presentation of his school’s theosophy (translated from the Persian):
If there are certain obscurities in my propositions, it is not because my writing is difficult; know, however, that all the ancient philosophers before me, being affeared of ignorant people, expressed their ideas through arcane means whose allusions are grasped by erudite folk. To explain our philosophy, we have gainfully utilized Light and Darkness. And you should not think that this reference to Light and Darkness is connected with Mani, the unbelievers and Zoroastrians, because in the end the propositions of those folk lead to the denial of religion and culminate in dualism [the underscoring is ours]. 
Can one find a more flagrant refutation of the supposed recuperation of the ancient Zoroastrian wisdom by Sohrawardi? Let us not start to pretend that the second part of the discourse condemns the Zoroastrians solely through fear of Koranic orthodoxy. The discourse is sufficiently clear and the first part displays a method of dissimulation whose avowal was already dangerously subversive in the eyes of the mollahs, rendering all other subterfuge unnecessary.
Had Sohrawardi wished to distance himself from the non-Muslim heretics to be favourably regarded by the mollahs, he could have rejected the “dualists” and “unbelievers”, but nothing obliged him to pinpoint the subjected minority Zardushtis (Zoroastrians) who had formerly fought against Manichaeism and came to be regarded, exceptionally, as “People of the Book”, Ahl al-kitab, by Iranian Islam. His error shows too that he mistakenly confounded the fundamental monotheism of the Avesta with Zurvanite dualism. Some obvious errors arise from his criticism of Zoroastrianism. The Zoroastrian doctrine was different — non-dualist — and opposed to many an idea of Manichaeism. As to the placing in parallel with that of the “unbelievers”, it is the very depths for one of the oldest and most venerable theist faiths in the world! Besides, the Zoroastrian faith hinged upon the worship of Truth (Rta/Arta/Asha) known even to the great Greek authors (Plato, Xenophon, Strabo), as a fundamental ethic of the ancient Persian wisdom which Sohrawardi had not retained (?) and who nevertheless denounced all subterfuge tending to dissimulate the source which nourished his own philosophy, whilst rejecting the pre-Islamic religions concerned as miscreated and heretical…
This capital text of Sohrawardi’s effectively shows that he had only the feeblest knowledge of the Zoroastrian religion which he accused of dualism (?) Most of all it proves that far from claiming kinship with Zoroastrianism, this Muslim gravely confounded (and reproved) the followers of Mani, dualists and atheists alike as Zoroastrians !
Against what H. Corbin believed to have grasped from Sohrawardi “as the will to continue the heritage of the Prophet and the Sages of Iran” because he utilized part of Avestic terminology to construct his very personal theosophy of Light, that which this Sunnite mystic, born in Azarbaijan and died in Syria, speaks of here is seen to be confirmed by the differences between Manichaeism, Zoroastrianism and the thinking of the “shaikh al-Ishraq”, in fact truly Sohrawardian, and its lacunae .
Besides, can the metaphysical speculations of Muslim mystics suggest mutatis mutandis that there could have been an assent or spiritual continuity from Mazdaean Iran to Shi’ite Iran, on the pretext that the second had unilaterally and in isolation recuperated certain concepts from the first? It is evident that the Shi’ite authors who had brought about this intellectual fantasy, had taken from Zoroastrianism whatever had served their very peculiar vision of Shi’ism, without lingering further on everything which, in the Avesta, totally went against this offensive assimilation of Mazdaean elements kneaded into an Islamic doctrine. By way of example, that Sohrawardi believed himself the “resurrector of the wisdom of ancient Persia” (H. Corbin), is an ill-considered formula to reduce the old Zoroastrian religion, ever-present in Iran and India, to Islamo-neo-Platonic speculations and to the later mix of Book IV of the Denkart, whereas the authentic Mazdaean religion and its descendants are purely and simply covered over in the operation.
H. Corbin wrote: «Sohrawardi, repatriating (?) the Hellenized Magi into an Iran become Islamic, marked eo facto the integration of the Iranian epic with the Abrahamic tradition» is hustling things somewhat, when all an occupied people and an ethnic group in diaspora still remain the legitimate heirs of the Iranian epic, an integral part of their religion and their history.
It is true that Zoroaster’s religion knew of many trials and regenerations of this kind throughout history, particularly in an Abrahamic setting?
To associate Sufism or Shi’ite mysticism with early Mazdaeism is to commit a serious confusion between an esoteric movement of a mystical vocation and an ancient mother-religion with a life-affirming philosophy and of the world whose ethic is opposed to contemplative Muslim asceticism.
Without doubting the spiritual values of Sufism, all attempts at identification of this movement of ascetic piety and renunciation of the world can only be made with Mazdaeism aside from a sound knowledge of the religion of Zarathushtra and its virile ethics. Above all, this syncretist procedure collides against the inability of the Muslim movement to emerge from Arabism and to distance itself from Koranic dogmatism, in particular the Shahadah, “abridgement of the Sufi doctrine and method” and to rid itself of its religious tradition, notably its spiritual filiations ascending directly to the Prophet through Hasan and Ali .
To sustain this thesis, one should retain of the Avestic thinking only what serves a particular vision, and build an isolated syncretism contradicted by inherent doctrines and events. It is also to seriously confound two radically different cultures: one a fundamentally agricultural society with elaborated structures where since Zarathushtra’s times the woman had a status unique in antiquity, and a nomadic and trading society, scorning land cultivation, practising slavery and extolling absolute masculine priority.
The Muslim thinkers who speculated on this philosophical fusion disregarded the Zoroastrians of Iran who were subjected to the persecutions and daily vexations of the occupier as well as those of the sizeable Indian diaspora . Moreover, they remained entirely in the margin of the Zoroastrian ethic which they claimed to fulfil in their Koranic schema. Thus, the Avestic good thoughts (humata) which they thought to possess in secretly “restoring” Zarathushtra’s thinking within a Muslim surrounding, they completely lacked its good utter¬ances (hukhta) and even more its good actions (huvarshta), meditation upon which urged them to act in favour of dispossessed Zoroastrians. This was also to ignore that the Pars is taken refuge in India had to intervene in favour of their Iranian cousins to the extent of obtaining the quashing in 1882 of the shameful jizya (the tax paid by infidels) imposed upon them by the Islamic regime from the time of the Arab conquest .
Above all, it hardly needs to be stated that one cannot claim to “restore” a religion in a hostile medium in the guise of a metaphysics elaborated upon an arbitrary and singularly different syncretism of this mystique, and to refuse to see what, in its very principles, is opposed to this spiritual assimilation.
How, for example, can one not invoke the Pahlavi books which, from the early centuries of Arab occupation, bear traces of an apologist confrontation with Islam, in particular with the speculative kalam of the Mu’tazilites? 
For defending the validity of these metaphysical connexions, can one disregard the typically Indo-Iranian structure of the Avesta? Or fail to recognize the Indo-European culture to the point of wishing to fuse together two such contradictory ideologies? Or again, to imagine that the tri-functional division of Indo-European religions and societies (demonstrated by Georges Dumezil) was assimilable by Islamic structures and the Koranic religion?
Even better, if there exists within Mazdaeism a concept truly irreducible to all Islamization, it is indeed that of the Victorious Light, of the Khvarenah (Persian Farrah), of the “Iranian Glory” which “belongs to Ahura Mazda”, and not to Allah and his Prophet, and which the demon Azhi Dahaka (Zohak) who in the Avesta represented the “Arab race” (sic) sought to vainly seize . Now, the theme of Victorious Light is very precisely the philosophy most laid claim to by the Muslim “ishraqiyun” theosophists . This “Aryan and Mazdaean Glory” (airyanem hvareno mazdadhatem) is “unseizable” (Yasht 19.45), which is to say it belongs to the sacred and inviolable heritage of pre-Islamic Mazdaean Iran (“to the Aryan peoples, born and to be born and to the saintly Zarathushtra”), and not only to the Kayanid sovereigns nor to the “Caliph of God upon His Earth” . The Iranian Glory may only come back to a sovereign, a tradition or a regime legitimately Mazdaean, and only in the inheriting of the Zoroastrian religion upto the Saoshyant (Soshans), the Saviour descended from Zarathushtra .
According to H. Corbin, Sohrawardi was conversant with the three spiritual categories of the Mazdaean Glory  Thereupon, a question arises: Did Sohrawardi and other claimants to this important Mazdaean concept in Iranian Islam know of the inviolable restrictions of the Avesta as outlined above? Interesting as is the thinking of Sohrawardi, whom the author does not reckon among the great ones of Persian philosophical history (see A. A. Halabi, op. cit.), its synthesis being everything one could wish for, it is not all from Zoroastrianism.
To invoke and sublimate these borrowings of Avestic dogmas and concepts by Shi’ite Islam, must one disregard as many “specialists on ancient Iran as specialists on Muslim philosophy” as H. Corbin claimed?  Indeed, the reason of this non-scientific proposition is that this daring theory has neither historical ground nor has it ever been accepted by the Zoroastrians themselves, because it merely lays on a tiny Shi’ite hermeneutical attempt at abusive syncretism.
If it is true that theological and philosophical elements from ancient Persia had transformed the thinking of Islam since the early centuries of its installation in Iran, it may be doubted that the theosophical speculations on Zoroastrian wisdom, transposed into an esoterical Islamic terminology, had rendered Shi’ism comparable with, and/or superior to Zoroastrianism.
Before the Islamic revolution in Iran, by forgetting history one could ignore the reality of Shi’ism. Above all, should one disregard the excesses to which the followers of this religious and political sect had so often abandoned themselves since the beginnings of the Shi’ah .
Must one also pass over in silence the lucid and prophetic judgement of the wise Montesquieu in the Esprit des Lois: «the religion of the Gabars (the Zoroastrians) had formerly made the kingdom of Persia to flourish: it corrected the evil effects of despotism … the Muhammadan religion today destroys that same empire» (XXIV.II)? Defenders of this sublimation of the ancient Persian wisdom in Iranian Islam, they would now invoke through a philosophical subtlety, that the Islam of the ayatollahs and mollahs reflects only the exoterism of the established religion which they would darken into an even greater contradiction since Shi’ism styles itself precisely as “the esoterism of Islam” according to the teachings of the Imams themselves .
It did not suffice for Mazdaean Iran to have been crushed by an Islam of the most “exoteric” and offensive kind; it must still be that in an “esoteric” milieu some of the unattached of Shi’ism lay claim to the faith of Zoroaster to “interpret it” in Koranic terminology, poetic but quite different.
Furthermore, last but not the least, it cannot be forgotten that today, as yesterday, any religion kills when it brings about a schizoid rupture between action and thought, when the ideological finality justifies the most barbaric means, in total contradiction to the Zoroastrian ethic by which the Sage of ancient Iran reconciled faith and deeds, to attempt the veritable moral and spiritual transfiguration of humanity, beyond the dream of esoteric speculation of this kind.