Zoroaster is credited with authorship of the Gathas as well as the Yasna Haptanghaiti, a series of hymns composed in his native Avestan dialect that comprise the core of Zoroastrian thinking. Little is known about Zoroaster; most of his life is known only from these scant 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 AD that historicizes legends and myths.