AETIUS (ah-et'i-oos) (fl. 35o), surnamed "the Atheist," founder of an extreme sect of Arians, was a native of Coele-Syria. He studied successively under the Arians, Paulinus, bishop of Antioch, Athanasius, bishop of Anazarbus, and the presbyter An tonius of Tarsus. At the first synod of Sirmium he won a dialectic victory over the homoiousian bishops, Basilius and Eustathius, who sought in consequence to stir up against him the enmity of Caesar Gallus. In 356 he went to Alexandria with Eunomius (q.v.) in order to advocate Arianism, but he was banished by Con stantius. Julian recalled him from exile, bestowed upon him an estate in Lesbos, and retained him for a time at his court in Constantinople. At the accession of Valens (364) he retired to his estate at Lesbos, but soon returned to Constantinople, where he died in 367. The Anomoean sect of the Arians, of whom he was leader, are sometimes called of ter him Aetians. His work De Fide has been preserved in connection with a refutation written by Epiphanius (Haer., lxxvi. 1o).
See A. Harnack, History of Dogma, vol. iv. passim.