2. An Egyptian bishop belonging to the seventh century.
He was first bishop of Phasis A. D. 620, and afterwards patriarch of Alexandria, A. D. 630-640.
It was owing to the favour of Heraclius, the emperor, that he was appointed over the latter place.
In 633 he attempted to make peace between the Theodosians or Severians and the Catholics, and for that purpose held a synod at Alexandria, in which he proposed a Libellus Satisfactionis in nine chapters.
This treatise was to be subscribed by the Theodosians, and then they were to be admitted into the bosom of the church.
But the seventh chapter favoured the Monotholite heresy, and led to much disputation.
In 638, Heraclius published an Ecthesis or formula of faith drawn up by Sergius, in which he clearly stated that there was but one will in Christ.
This was subscribed by Cyrus, a circumstance that served to confirm its truth in the eyes of many. Cyrus died A. D. 640. Besides the Libellus Satisfactionis, he wrote three letters to Sergius, patriarch of Constantinople, which are still extant. Both are printed in the Concilia, vol. vi.
Cave, Histor. Literary.
vol. i.; Murdock's Moshein,
vol. i.; Guerike's Handbuch,
vol. i.; Gieseler's Text-book,
by Cunningham, vol. i.