Kapadia divulges another fact, "You need to distinguish between the Parsis, who are by definition those whose father is a Parsi, and Zoroastrians, who are followers of the religion, initiated by Zarathushtra
Pithawala, "Era of Lord Zarathushtra - As Deciphered from the Letters in His Holy Name," in: N.
Bulsara, The Religion of Zarathushtra as Taught by Himself and His Disciples (Bombay, 1938).
and His Antagonists: A Sociolinguistic Study with English and German Translation of His Gathas.
Heidel-berg: Winter, 1959), his 1991 re-edition includes the YH, as the title suggests (The Gathas of Zarathushtra
and the Other Old Avestan texts, Heidelberg: Winter, 1991), and the three volumes of Jean Kellens and Erie Pirart's Les text vieil-avestiques (Wiesbaden: Reichert, 1988, 1990, 1991) also treat it along with the Gathas.
That dichotomy appears to have been initially personified, although not in absolute dualist terms, by the devotional poet who later came to be regarded as a prophet, namely Zarathushtra
(Zoroaster, sometime ca.
The Gathas of Zarathushtra
and the Other Old Avestan Texts, part I: Introduction--Text and Translation; part II: Commentary.
However, with regard to similarities between the birth stories of Muhammad and Zarathushtra
Zoroastrian eschatology clearly had roots in the preachings of the prophet Zarathushtra