Acacius (surnamed Monophthalmus, from his having but one eye), was the disciple of Eusebius of Caesarea, in Palestine, whom he succeeded in the see of Caesarea in 340. He was one of the chiefs of the Arian party, and a man of ability and learning, but unsettled in his theological opinions. He was deposed as an Arian by the Synods of Antioch (A.D. 341) and Seleucia (359). Subsequently he subscribed the Nicene creed, and therefore fell out with the Anomaeans, with whom he had before acted. He died A.D. 363. St. Jerome (de Scrip. cap. 98) says that he wrote seventeen books of commentaries upon Holy Scripture, six on various subjects, and very many treatises, among them his book Adversus Marcellum, a considerable fragment of which is contained in Epiphanius, Haeres. 72. Socrates (lib. 2, cap. 4) says that he also wrote a life of his predecessor, Eusebius. — Cave, Hist. Lit. anno. 340; Lardner, Works, 3, 583.