Mazdaism (also known as Zoroastrianism or the religion of Zarathustra) is one of the world's oldest religions. Its historical and geographical origins are highly disputed. The historicity of its founder, Zarathustra, has been called into question, as has the traditional interpretation of the religion's founding texts, the Avesta. The antiquity of the religion has ensured it an important place among historians of ancient world religions. This is not the case for the non-imperial history of Mazdeism, which begins with the Arab conquests of Iran and the Islamization of the Iranian world. The fact that Mazdean communities occupied only a marginal place in Islamized Iranian society (and in Indian society for Parsis) until their "rediscovery" by European travelers and their emancipation in the 19th (for Parsis) and 20th (for Iranian communities) centuries, has allowed historians to see them as a "remnant" of a greater past, to forget or ignore them.
As a result, almost half of the history of Mazdeism has been left to a few specialists, or not studied at all. The religion is known substantially as it was in the late Sassanid period and the early centuries of Islam. This image of religion has been used both to interpret earlier religious expressions (especially Achaemenid and Parthian), and to measure later developments. This has produced a stationary image of the whole religion.
In recent decades, however, the general history of Mazdaism (from its origins to the present day) has been written twice, by Mary Boyce and Michael Stausberg. The former has brought all her historical and philological powers to bear, but her thesis of a great historical continuity produced by the prophet Zarathustra's readings has provoked many objections. The second has largely confined itself to a descriptive approach. We are still faced with the question posed almost fifty years ago by Marijan Molé: is a history of Mazdeism possible?
In these four lessons, we shall formulate an answer to Molé's question: a history of Mazdeism is only possible when we recognize four distinct phases and endeavor to consider what the links between these phases might have been. First place must be given to sociological considerations and to the project of rethinking the importance and use of so-called sacred texts, which have been the focus of Western scholarly interest.