Eusebius, surnamed PAMPHILI, an ecclesiastical writer of the early church, born in Palestine about 265, died about 340. But little is known of his youth, save that he began his studies in Antioch, then visited the Thebaid, where he spent some time in completing his knowledge of Scripture and theology, after which he opened a school at Caesarea. A splendid library founded or much enlarged by the bishop Pamphilus, his protector, enabled Eusebius to collect vast treasures of erudition. In the persecution of Diocletian (303) he fled from the city, but soon returned for the purpose of ministering to the wants of Pamphilus, who had been cast into prison, and was in 309 put to death. Eusebius assumed his name in memory of their friendship. Pauli-nus, bishop of Tyre, next gave him an asylum, but persecution drove him into Egypt, where he suffered imprisonment until the abdication of Diocletian set him free, and allowed him to return to Caesarea, of whose church he became bishop in 315. About this time some points of resemblance between his theological views on the Trinity and those of the heresi-arch Arius caused him to contract a friendship for the latter. At the council of Nice he sat at Constantine's right hand, and made the first draft of the Nicene creed.

He subscribed the solemn profession of faith in the divinity of the Son, with a reservation founded on a confusion of the eternal birth of the Logos with the temporal birth of the incarnate Word, but he refused peremptorily to subscribe the decrees condemnatory of the Arian doctrine. A letter which he addressed to his diocesans after the council in explanation of his position and his views, together with his unremitting exertions in favor of Arius, caused him to be accused of heresy. His formulas and terminology continued to be employed by the Semi-Arians long after he had himself given expression to more orthodox opinions in his work De Ecclesiastica Theologia. In the long Arian controversies subsequent to the council of Nice he was the uncompromising opponent of Athanasius. He prevailed on the emperor to convene a council in 331 in Caesarea, before which Athanasius was summoned, but refused to appear, and was accused by Eusebius of disobedience to the laws of the empire. His influence with Constantine caused a second council to be assembled in Tyre in 335, in which he urged and obtained the deposition of Atha-nasius, and afterward procured his banishment to Gaul. On Sept. 14, 335, the bishops who had composed the council of Tyre assembled in Jerusalem for the dedication of a new church.

Eusebius pronounced on the occasion his "Panegyric of Constantine," caused Arius to be admitted to the communion of the church, and wrote to the bishops of Christendom to inform them of these proceedings. Shortly after this the same prelates met in Constantinople under the leadership of Eusebius, who had Marcellus, bishop of Ancyra, condemned for Sabellianism, and besought in vain Alexander, bishop of the imperial city, to receive Arias solemnly to his communion. After witnessing the tragic death of Arius on this occasion, Eusebius returned to Caesarea, and continued until his death with equal assiduity the publication of his great works and his opposition to Athanasius. He has been justly called the father of ecclesiastical history. Theological writers, both ancient and modern, are much divided with regard to his orthodoxy; some, like the historians Sozomen and Socrates, defend him strenuously; while others, with St. Jerome, Photius, and the seventh general council, condemn him as a heretic. His principal works are: "A Defence of Origen," in six books, in the first five of which the bishop Pamphilus cooperated; "Evangelical Preparation," in 15 books, and the "Evangelical Demonstration," in 20; Chronicon, a conspectus of universal history down to the 20th year of Constantine; "Ecclesiastical History;" a "Life of Constantine;" five books " On the Incarnation;" " Commentaries on Isaiah;" Onomasticon, or a nomenclature of nations according to the Hebrew books; 30 books "Against Porphyrius;" "Topics;" "Topography of Judea and the Temple;" "Commentaries on the Psalms;" "Concordance of the Four Gospels;" " Commentary on the First Epistle to the Corinthians;" and " Treatise on the Fulfilment of Christ's Prophecies." His Chronicon was translated into Latin by St. Jerome, who continued it down to the sixth consulate of Valens and Valentin-ian; and it was published by Scaliger (2 vols. fol., Amsterdam, 1G58). The whole work was in a fragmentary state until the discovery in 1784 of an Armenian version, which was published by Mai and Zohrab in 1818, and explained afterward by Niebuhr. His "Ecclesiastical History " was continued by Sozomen, Socrates, and Theodoret, and translated by Rufinus into Latin, and brought down to 395 (Rome, 1474). The principal editions are those of Stephens (Paris, 1544), Valois (Paris, 1G59), Reading (Cambridge, 1720), Heinichen (3 vols. 8vo, Leipsic, 1827), and Burton (Oxford, 1838; reprinted, with an introduction by W. Bright, Oxford, 1872). It has been translated into French by Louis Cousin; into German by Hedio (1545) and Stroth (1778); and into English by Hanmer (1577), Parker (1703), Cater (1736), Dalrymple (1778), and Cruse (reprinted in Bohn's "Ecclesiastical Library"). A Greek edition (with Latin translation) of the complete works of Eusebius is contained in Migne's Patrologia Groeca (Paris, 1857-'66, vols. xix. to xxiv.). The best Latin edition of the works then extant is that of Paris, 1581.