"Zoroaster (/ˈzɒroʊæstər/, UK also /ˌzɒroʊˈæstər/; Greek: Ζωροάστρης, Zōroastrēs), also known as Zarathustra (/ˌzærəˈθuːstrə/, UK also /ˌzɑːrə-/; Avestan: Zaraθuštra), Zarathushtra Spitama or Ashu Zarathushtra (Modern Persian: زرتشت, Zartosht), was an ancient Iranian prophet (spiritual leader) who founded what is now known as Zoroastrianism. His teachings challenged the existing traditions of the Indo-Iranian religion and inaugurated a movement that eventually became the dominant religion in Ancient Persia. He was a native speaker of Old Avestan and lived in the eastern part of the Iranian Plateau, but his exact birthplace is uncertain.
There is no scholarly consensus on when he lived. Some scholars, using linguistic and socio-cultural evidence, suggest a dating to somewhere in the second millennium BCE. Other scholars date him in the 7th and 6th century BCE as a near-contemporary of Cyrus the Great and Darius I. Zoroastrianism eventually became the official religion of Ancient Persia and its distant subdivisions from the 6th century BCE to the 7th century CE. Zoroaster is credited with authorship of the Gathas as well as the Yasna Haptanghaiti, hymns composed in his native dialect, Old Avestan and which comprise the core of Zoroastrian thinking. Most of his life is known from these texts. By any modern standard of historiography, no evidence can place him into a fixed period and the historicization surrounding him may be a part of a trend from before the 10th century CE that historicizes legends and myths."
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"Abraham Valentine Williams Jackson, L.H.D., Ph.D., LL.D. (February 9, 1862 – August 8, 1937) was an American specialist on Indo-European languages.
He was born in New York City on February 9, 1862. He graduated from Columbia University in 1883. He was a fellow in letters there from 1883 to 1886, and an instructor in Anglo-Saxon and the Iranian languages from 1887 to 1890. After study at the University of Halle from 1887 to 1889 he became an adjunct professor of English language and literature. In 1895, he was appointed public lecturer and also appointed to the newly founded professorship of Indo-Iranian languages at Columbia University, where he remained until 1935.
He was well known as a lecturer on English literature and the Orient. In 1901, during a visit to India and Ceylon, he received special attention from the Parsees, who presented to Columbia a valuable collection of Zoroastrian manuscripts in recognition of the instruction there given by him in their ancient texts. In 1903 he made a second journey to the Orient, this time visiting Iran. He also visited Central Asia sometime before 1918.
Jackson's grammar of Avestan, the language used in the Zoroastrian scriptures, is still considered to be the seminal work on the topic. Jackson was one of the directors of the American Oriental Society.
He died on August 8, 1937."
(from Wikipedia)
Zoroaster, the Prophet of Ancient Iran