heresiarch

noun

1. The founder of a heresy, or a major ecclesiastical proponent of such a heresy.

   “He died in 1223, and seems to have had no successor; not is it an ascertained point that more than one such hæresiarch was ever recognized.”

   “Sermons, whose writers played such dangerous tricks / Their own heresiarchs called them heretics, […]”

   “Nestorǐus, a celebrated Haeresiarch, was appointed patriarch of Constantinople a.d. 428, but in consequence of his heresy was deposed at the council of Ephesus, 431. […] Nestorius carefully distinguished between the divine and human nature attributed to Christ, and refused to give to the Virgin Mary the title of Theotocus (Θεοτόκος) or "Mother of God."”

   “Beautiful as Mr. [James Allanson] Picton's book was, its tendency was away from Christianity, and, followed to its logical conclusions, led to the renunciation of the Christian faith. He was illustrating an old truth, though to me then an undiscovered one, that a heresiarch may be, and often is, a very noble man, whatever may be the result to society of his views.”