leading prelate of Gaul and a celebrated preacher whose opposition to the heresy of semi-Pelagianism (q.v.) was one of the chief influences on its decline in the 6th century.

At age 20, he entered the monastery at Lérins, Fr., and, having been ordained priest, he became abbot of a monastic community on an islet in the Rhône River near Arles. Caesarius succeeded his kinsman Aeonius as archbishop of Arles, the see of which Pope Symmachus made primatial for Gaul and Spain. As primate, Caesarius convened various regional synods of importance, among which the second Council of Orange (529) is a landmark in the history of dogma because it decisively rejected Semi-Pelagian theories in favour of a moderate Augustinianism. Caesarius was no great theologian, but he was a great preacher whose many sermons were preserved and frequently used after his death. He wrote a directory for monks and a rule, Regula ad virgines, for the women's monastery of St. John's (later named after St. Caesarius), which he established and where he appointed his sister, St. Caesaria, as abbess.