Background
Saint was born in Rome, Italy.
Saint was born in Rome, Italy.
During the reign of Zephyrinus he acquired great influence in the Church, chiefly by opposing modalism, a doctrine holding that the Trinity represented only one person in three modes, or aspects.
Callistus was elected to succeed Zephyrinus as pope in 217. He became an energetic pontiff, particularly in establishing and codifying Church doctrine regarding the nature of the Trinity. He condemned modalism as heretical and excommunicated Sabellius, its most prominent champion. He also clashed with St. Hippolytus on the question of the Trinity, a quarrel that resulted in Hippolytus' setting himself up as the first antipope. It is believed that Callistus died a martyr. His feast day is October 14.