Martyr; antipope from 217 to 235; died Sardinia in 236. Little historically certain is known of his life due to the discordant traditions which are extant. After the death of Pope Zephyrinus he secured his election by a small band of followers in opposition to Callistus I whom he considered a heretic. He remained anti-pope during the reigns of Pope Urban I and Pope Pontian, and was banished to Sardinia in 235, where he became reconciled with the Church. Hippolytus was one of the most important and prolific theological writers of the Roman Church in the pre-Constantinian era. Most of his writings have been lost but his "Philosophumena" (Refutation of all Heresies) was discovered in a monastery at Mount Athos in 1842. Of the ten books the second, third, and part of the fourth are missing. The Philosophumena is written in Greek, as are all his writings, and discusses the early heresies under five headings: Ophites; Simonists; Basilidians; Docetae; Noetians. It comprises the most valuable source for the history of the early heresies. Feast, Roman Calendar, August 22,.