Bishop of Caesarea in Palestine, disciple and biographer of Eusebius, the historian, whose successor in the See of Caesarea he became in 340. Nothing is known of the date or country of his birth, but he was probably a Syrian; and throughout his life bore the nickname of monophthalmos (one-eyed); no doubt from a personal defect (S. Hier. Viri III., XCVIII), but possibly with a maliciously figurative reference, also, to his general shiftiness of conduct and his rare skill in ambiguous statement. He was a prelate of great learning, a patron of studies (S. Hier., Epist. ad. Marcellam, 141), and was the author of a treatise on Ecclesiastes. He also wrote six books of miscellanies (symmikta zetemata) or essays on various subjects which have come down to us only in fragments. The student may consult these fragments in detail in Fabricius, "Bibliotheca Graeca", vii, 336, and ix, 254 sqq. (ed. Harless). He is remembered chiefly for his bitter opposition to St. Cyril of Jerusalem and for the part he was afterwards enabled to play in the more acute stages of the Arian controversy. There is a significant passage in the famous twenty-first oration of St. Gregory Nazianzen, in which that champion of orthodoxy speaks of "the tongue of the Arians" (Orat., xxi, 21) in dubiously complimentary terms.

If, as seems probable, it is Acacius who is there referred to, it can only be said that the story of his career fully justifies the implication so darkly made. He was one of those imperial prelates so effectively described by Newman (Arians 4th Cent., 4th ed., 274) as "practised in the gymnastics of the Aristotelic school"; and his readiness in debate and genius for intrigue, joined to the prestige he already possessed as the friend and successor of the great Church historian of Caesarea, naturally singled him out as the likeliest spokesman and guiding spirit of the Court faction, even before their first great leader, Eusebius of Nicomedia, had passed away. He was one of the notorious "ninety" who signed the ambiguous creeds at Antioch, in the presence of Constantius in 341 (Sozomen, III, v), on the occasion of the dedication of the Golden Basilica. For his part in this transaction and for his open advocacy of a policy of reticence towards the Nicaean formula, we find his name mentioned in the list of those who were deposed by the Council of Sardica in 347 (Athanasius, Hist. Ar., XVII; Epist. ad. Ægypt., VII). Refusing to acquiesce in the sentence passed upon him, he withdrew with the other bishops of the Court faction to Philippopolis, where he in turn helped to secure a sentence of excommunication and deposition against his judges and also against Pope Julius, the patron and defender of St. Athanasius, and against Hosius of Cordova (Soc., II, xvi; Soz., III, xiv; Theod., II, xxvi; Labbe, Conc., II, 625-629). These penalties which were inflicted on him at the hands of the orthodox did nothing, of course, to diminish his prestige. If we may trust the testimony of St. Jerome, his credit with Constantius was so great during all these years that when Pope Liberius was deposed and driven into exile, in 355 or 357, Acacius was able to secure the intrusion of Felix the Antipope in his place.

The year 358 marks the culmination of his acrimonious and undignified quarrel with Cyril of Jerusalem. The misunderstanding, which dated. back to a period not long after Cyril's installation, had arisen ostensibly. over a question of canonical precedence, but was most probably rooted in the chagrin that Acacius characteristically felt at being unable to sway Cyril's policy entirely to his own liking. Charges and counter-charges of heresy followed for some years, until Acacius managed to secure the deposition of Cyril, through the assistance of the Palestinian bishops, whom he had induced to examine a wholly ridiculous charge of contumacy. Cyril went into exile, but was restored to his church within two years by a decision of the famous Council of Seleucia. But the extraordinary credit enjoyed by Acacius with the weak-minded Constantius was able to undo this act of ordinary justice, and, in 360, Cyril was condemned once more — this time through the influence which Acacius was able to exercise at the Synod of Constantinople. Cyril was forced to yield. He left his see and remained in exile until the accession of Julian, in 361. The fact, however, that Acacius received a temporary check in the reinstatement of Cyril, at the hands of the Synod of Seleucia, must not blind the reader to the real weight of his influence either in the Council itself or in the ecclesiastical politics of the time. He was among the foremost of the Arianizing prelates who succeeded in carrying through the idea of a divided Synod to solve the problems created by the Sirmian manifesto. In this sense he may be charged with the bulk of the mischief created by the definitions of Ariminum and Seleucia. The turbulent and unscrupulous faction which rallied to the support of his ideas in both gatherings was entirely his creation and rightly bore his name — oi peri Akakion.

The detailed account of his activities at Seleucia belongs rather to the history of that gathering than to the present sketch of his life; but some notice of his mode of procedure will not be out of place here. The number of bishops present has been variously estimated as somewhere between one hundred and fifty and one hundred and sixty (Gwatkin, Studies in Arianism, V, note G, where the original authorities are ably discussed). The Semi-Arians were in a large majority; and Acacius had a well-disciplined following, which, with the Anomoeans whom he had won to his side, by holding out hopes of a compromise, amounted to some forty in all. The first critical stage of events was soon marked by the re-adoption of the Semi-Arian Creed of Antioch, known popularly as the "Creed of the Encaenia", or "Creed of the Dedication" (he en tois egkainiois) which was a negatively unsatisfactory profession of faith — the only distinct character about it being that it was Anti-Nicene in scope and had been framed by men who had deliberately confirmed the deposition of St. Athanasius. The next stage of events was more significant still; for it gave Acacius and his followers the opportunity to reveal their strength. Silvanus of Tarsus proposed to confirm the famous Lucianic Creed, when Acacius and his party arose and left the assembly, by way of protest. In spite of this move the Creed was signed the next morning with closed doors; a proceeding which Acacius promptly characterized as a "deed of darkness." On Wednesday Basil of Ancyra and Macedonius of Constantinople arrived with Hilary of Poitiers, Cyril of Jerusalem, and Eustathius. Cyril was already under censure; and Acacius refused to bring his followers back to the synod until he and some other accused bishops who were present had withdrawn. After a stormy debate his plan was agreed to and Leonas, the Comes, or representative of Constantius at the deliberation, rose and read a copy of a new Creed which Acacius had put into his hands. While not expressly repudiating the Lucianic formulas, it nevertheless objected to the terms homoousion and homoiousion as being alike unscriptural. This led to a very heated discussion, and on Thursday Acacius found himself bluntly attacked by Eleusius, the ex-soldier and Semi-Arian Bishop of Cyzicus.

On Friday Acacius refused once more to take part in any further deliberations and Leonas joined with him, on the plea, as he averred, that the Emperor had not sent him to preside over a council of bishops who could not agree among themselves. The majority thereupon convened without them and deposed Acacius and some fifteen other prelates. That astute leader, however, did not wait for the formal vote of deposition against him, but set out immediately, with eight others, for Constantinople. On arriving there he discovered that his object had already been secured by the advent of a number of disaffected deputies from Ariminum. The famous conference of Niké (near Hadrianople) had taken place and the homoios, without the supposed safeguard of the kata panta, had been adopted. This led to a fresh synod held at the suggestion of Constantius in the imperial city itself. It meant the complete triumph of the indefatigable Acacius. Homoean ideas were established at Constantinople; and, although their influence never lasted very long in the West, they enjoyed a fluctuating but disquieting supremacy in the East for nearly twenty years longer. Acacius returned to his see in 361 and spent the next two years of his life in filling the vacant sees of Palestine with men who were thought to sympathize with his policy of theological vagueness and Anti-Nicenism. With characteristic adroitness he consented to a complete change of front and made a public profession of adherence to the Nicaean formularies on the accession of Jovian in 363. When the Arian Valens was proclaimed Augustus in 364, however, Acacius once more reconsidered his views and took sides with Eudoxius; but his versatility this time served him to little purpose. When the Macedonian bishops met at Lampsacus, the sentence previously passed against him was confirmed and he is heard of no more in authentic history. Baronius gives the date of his death as 366.

For bibliography see ACACIANS.

CORNELIUS CLIFFORD