With the growth of our knowledge of the language of the sacred texts, we have now a clear idea also of the history of Zoroastrian literature and of the changes and chances through which with varying fortunes the scriptures have passed. The original Zoroastrian Avesta, according to tradition, was in itself a literature of vast dimensions. Pliny, in his 'Natural History,' speaks of two million verses of Zoroaster; to which may be added the Persian assertion that the original copy of the scriptures was written upon twelve thousand parchments, with gold illuminated letters, and was deposited in the library at Persepolis. But what was the fate of this archetype? Parsi tradition has an answer. Alexander the Great--"the accursed Iskander," as he is called--is responsible for its destruction. At the request of the beautiful Thais, as the story goes, he allowed the palace of Persepolis to be burned, and the precious treasure perished in the flames. Whatever view we may take of the different sides of this story, one thing cannot be denied: the invasion of Alexander and the subjugation of Iran was indirectly or directly the cause of a certain religious decadence which followed upon the disruption of the Persian Empire, and was answerable for the fact that a great part of the scriptures was forgotten or fell into disuse. Persian tradition lays at the doors of the Greeks the loss of another copy of the original ancient texts, but does not explain in what manner this happened; nor has it any account to give of copies of the prophet's works which Semitic writers say were translated into nearly a dozen different languages. One of these versions was perhaps Greek, for it is generally acknowledged that in the fourth century B.C. the philosopher Theopompus spent much time in giving in his own tongue the contents of the sacred Magian books.