CALIXTUS I., or Callistus III, pope from 217 to 222, was little known before the discovery of the book of the Philosophumena. From this work, which is in part a pamphlet directed against him, we learn that Calixtus was originally a slave and engaged in banking. Falling on evil times, he was brought into collision with the Jews, who denounced him as a Christian and procured his exile to Sardinia. On his return from exile he was pensioned by Pope Victor, and, later, was associated by Pope Zephyrinus in the government of the Roman church. On the death of Zephyrinus (217) he was elected in his place and occupied the papal chair for five years. His theological adversary Hippolytus, the author of the Philosophumena, accused him of having favoured the medalist or Patripassian doctrines both before and after his election. Calixtus, however, condemned Sabellius, the most prominent champion of that system. Hippolytus accused him also of certain relaxations of discipline. It appears that Calixtus reduced the penitential severities applied until his time to those guilty of adultery and other analogous sins. Under Calixtus and his two immediate successors, Hippolytus was the leader of a schismatic group, organized by way of protest against the election of Calixtus. Calixtus died in 222, in circumstances obscured by legends. In the time of Constantine the Roman church reckoned him officially among the martyr popes.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)