ACACIUS OF CAESAREA: One of the most influential bishops in the large middle party which opposed the Nicene Creed during the Arian controversy. He was the disciple of Eusebius, and his successor in the bishopric of Csesarea. He took part in the Eusebian synod at Antioch in the spring of 341, and in another at Philippopolis in 343. By the orthodox council of Sardica in the same year he was regarded as one of the heads of the opposing party, and threatened with deposition. Common opposition to the Nicene doctrine held the party together until about 356. Thus, on the death of Maximus of Jerusalem (350 or 351), Acacius helped to get the vacant see for Cyril, who belonged rather to the opposite wing of the party, the later Homoiousians or Semi-Arians. That he fell out with Cyril and procured his deposition (357 or 358) was due partly to jealousy between the two sees, partly to the changed attitude of parties under Constantius (351-361). The two wings fell apart, and Acacius became the leader of the court party, the later Homoians, in the East. In 355 he seems to have been one of the few Easterns who represented the emperor at the Council of Milan; and, according to Jerome, his influence with Constantius was so great that he had much to do with setting up Felix as pope in the place of the banished Liberius. After the so-called Second Council of Sirmium (357) had avoided the controverted terms altogether and said nothing about the ousia ("substance"), it was undoubtedly Acacius who at the Council of Antioch (358) influenced Eudoxius to accept this compromise for the East. At the Synod of Seleucia (359) he took a prominent part. In obvious concert with the imperial delegates, he seemed to favor what Ursacius and Valens tried to carry in the Synod of Rimini, the acceptance of the so-called third Sirmian formula ("similar [homoios] according to the Scriptures . . . similar in all things"). He and his party, it is true, expressly condemned the anomoios ("dissimilar") theory, but they omitted the "in all things," which agreed as little with the real views of Acacius as with those of the Western Homoians. The council ended in a schism; the Homoiousian majority, in a separate session, deposed Acacius and other leading Homoians. But he was in touch with the court; and at the discussions in Constantinople which continued those of Seleucia, the imperial wishes, represented by Acacius, Ursacius, and Valens, prevailed. He was able to celebrate his victory the next year at the Council of Constantinople, and commanded the situation in the East. With the death of Constantius the day of this imperial orthodoxy was done; and under Jovian (363-364) Acacius succeeded in accepting the Nicene orthodoxy which was now that of the court. His name appears among the signatures of those who, at the Synod of Antioch presided over by Meletius (363), accepted the Nicene formula in the sense of homoios kat' ousian ("similar as to substance"). With the accession of the Arian Valens (364), the situation changed once more; and apparently Acacius changed with it. He and his adherents were deposed by the Homoiousian Synod of Lampsacus (365), after which he is heard of no more; probably he soon died. He was a voluminous writer, but nothing remains except the formula of Seleucia, a fragment in Epiphanius (Adversus haereses, lxxii. 6-10; MPG, xlii. 589-596) of his polemic against Marcellus, and scattered quotations in some of the Catenae. (F. Loofs.)
Along with Eunomius and Aetius, Acacius may be said to have given dialectic completeness to Arianism. In their polemics against the Nicene Symbol they laid chief stress on the fact that the Father was "unbegotten," depending for his being neither upon himself nor another, which could not be said of the Son. They insisted also upon the complete comprehensibility of God. A. H. N.