As to the age of these books, however, and the period at which Zoroaster lived, there is the greatest difference of opinion. He is mentioned by Plato (Alcibiades, I. 37), who speaks of "the magic (or religious doctrines) of Zoroaster the Ormazdian" (_magedan Zoroastran ton Oromazon_[120]). As Plato speaks of his religion as something established in the form of Magism, or the system of the Medes, in West Iran, while the Avesta appears to have originated in Bactria, or East Iran[121], this already carries the age of Zoroaster back to at least the sixth or seventh century before Christ. When the Avesta was written, Bactria was an independent monarchy. Zoroaster is represented as teaching under King Vistaçpa. But the Assyrians conquered Bactria B.C. 1200, which was the last of the Iranic kingdoms, they having previously vanquished the Medes, Hyrcanians, Parthians, Persians, etc. As Zoroaster must have lived before this conquest, his period is taken back to a still more remote time, about B.C. 1300 or B.C. 1250[122] It is difficult to be more precise than this. Bunsen indeed[123] suggests that "the date of Zoroaster, as fixed by Aristotle, cannot be said to be so very irrational. He and Eudoxus, according to Pliny, place him six thousand years before the death of Plato; Hermippus, five thousand years before the Trojan war," or about B.C. 6300 or B.C. 6350. But Bunsen adds: "At the present stage of the inquiry the question whether this date is set too high cannot be answered either in the negative or affirmative." Spiegel, in one of his latest works,[124] considers Zoroaster as a neighbor and contemporary of Abraham, therefore as living B.C. 2000 instead of B.C. 6350. Professor Whitney of New Haven places the epoch of Zoroaster at "least B.C. 1000," and adds that all attempts to reconstruct Persian chronology or history prior to the reign of the first Sassanid have been relinquished as futile.[125] Döllinger[126] thinks he may have been "somewhat later than Moses, perhaps about B.C. 1300," but says, "it is impossible to fix precisely" when he lived. Rawlinson[127]| merely remarks that Berosus places him anterior to B.C. 2234. Haug is inclined to date the Gâthâs, the oldest songs of the Avesta, as early as the time of Moses.[128] Rapp,[129] after a thorough comparison of ancient writers, concludes that Zoroaster lived B.C. 1200 or 1300. In this he agrees with Duncker, who, as we have seen, decided upon the same date. It is not far from the period given by the oldest Greek writer who speaks of Zoroaster,--Xanthus of Sardis, a contemporary of Darius. It is the period given by Cephalion, a writer of the second century, who takes it from three independent sources. We have no sources now open to us which enable us to come nearer than this to the time in which he lived.