scientific text portions of the Avesta that were in the possession of the Greeks. Under Shapur II, Arderbad Mahrespandand revised the canon to ensure its orthodox character, while under Khosrow I, the Avesta was translated into Pahlavi. The compilation of the Avesta can be authoritatively traced, however, to the Sasanian Empire, of which only fraction survive today if the Middle Persian literature is correct. The later manuscripts all date from after the fall of the Sasanian Empire, the latest being from 1288, 590 years after the fall of the Sasanian Empire. The texts that remain today are the Gathas, Yasna, Visperad and the Vendidad, of which the latter's inclusion is disputed within the faith. Along with these texts is the individual, communal, and ceremonial prayer book called the Khordeh Avesta, which contains the Yashts and other important hymns, prayers, and rituals. The rest of the materials from the Avesta are called "Avestan fragments" in that they are written in Avestan, incomplete, and generally of unknown provenance. Middle Persian (Pahlavi) Middle Persian and Pahlavi works created in the 9th and 10th century contain many religious Zoroastrian books, as most of the writers and copyists were part of the Zoroastrian clergy. The most significant and important books of this era include the Denkard, Bundahishn, Menog-i Khrad, Selections of Zadspram, Jamasp Namag, Epistles of Manucher, Rivayats, Dadestan-i-Denig, and Arda Viraf Namag. All Middle Persian texts written on Zoroastrianism during this time period are considered secondary works on the religion, and not scripture. Nonetheless, these texts have had a strong influence on the religion. Zoroaster Zoroastrianism was founded by Zoroaster (or Zarathushtra) in ancient Iran. The precise date of the founding of the religion is uncertain and estimates vary wildly from 2000 BCE to "200 years before Alexander". Zoroaster was born - in either Northeast Iran or Southwest Afghanistan - into a culture with a polytheistic religion, which featured excessive animal sacrifice. and the excessive ritual use of intoxicants, and his life was influenced profoundly by the attempts of his people to find peace and stability in the face of constant threats of raiding and conflict. Zoroaster's birth and early life are little documented but speculated upon heavily in later texts. What is known is recorded in the Gathas, forming the core of the Avesta, which contain hymns thought to have been composed by Zoroaster himself. Born into the Spitama clan, he refers to