Saint Callixtus I (also referred to as Callistus I) was elected as the sixteenth Bishop of Rome, in AD217, succeeding Pope Zephyrinus. During the papacy of Pope Zephyrinus, Callixtus remained his close aide and participated in the former Pontiff’s efforts to protect the Church's doctrines from heresies.

Historians testify that Pope Callixtus remained as a slave in the household of a Christian official in the Roman court. He was at first incharge of the financial matters of the household. Upon incurring a financial loss, he had to flee from his Master, was later caught and returned to the household. However, a quarrel with a Jew saw him being sent to the Sardinian mine as a forced slave labourer.

It was Pope Victor I’s campaign to release all Christians in forced slavery in mines that earned him his freedom. Although his name did not appear in Pope Victors I’s list of slaves to be released, Callixtus’s insistence that he too should be freed convinced the Roman governor to free him from slavery. He was later sent to a place called Anzio by Pope Victor I.

Pope Zephyrinus, who had succeeded Pope Victor I, recalled Callixtus to Rome and ordained him a deacon. Callixtus assisted Pope Zephyrinus in his administrative affairs and provided material and theological assistance in dealing with heresies. Thus, Callixtus became the Pope's chief adviser and archdeacon.

Saint Hippolytus was highly critical of Pope Zephyrinus and Callixtus and also reluctant to accept the Pope's teachings in their entirety. When Callixtus assumed Papacy after the demise of Pope Zephyrinus, Saint Hippolytus declined to accept his election. Hippolytus proclaimed himself a Pope and thus became the first anti-pope, breaking away from the church in AD235. During the reign of Pope Callixtus, Saint Hippolytus turned out to be his greatest opponent.

Theological differences and debates further deepened the division between these two great personalities. While Saint Hippolytus taught that only Christ, the Son of God, was incarnated, Pope Callixtus believed that both the Father and the Son were incarnated. Such divergent studies and views led Saint Hippolytus to declare himself as the first Antipope in the history of the Church. In AD235, Saint Hippolytus realized his mistake and returned to the church and afterwards attained Martyrdom.

Callixtus's election as pope was made more acceptable by his gentle and merciful approach to sinners who accepted him. Many sins that were considered unforgivable (murder, adultery) were forgiven by Pope Callixtus for the love of Christ and absolution for those who committed such sins. After making atonement such persons were to receive the Eucharist. His compassionate approach even led to relaxation of marriage laws.

Pope Callixtus allowed marriages between women of the higher castes and men of the lower castes (commoners, slaves) in the Church, which was unthinkable at the time and strictly against the Roman law. Many of his actions and decisions of such kind made Saint Hippolytus to assume that the Pope was a heretic.

Pope Callixtus' short reign was filled with many controversies and problems. He was called to eternal rest in AD222.
-edit & trans. SM