Semi-Arians a sect which arose in the 4th century, holding a modified form of Arianism. It was founded by Eusebius of Caesarea and the sophist Asterius. They were opposed alike to the strict definition of orthodox Nicene theologians like St. Athanasius, and to the equally strict definition which characterized the logical intellectualism of the old Arians. Its symbol was the Homoiousion, which they substituted for the orthodox Homoousion; that is, the Son was regarded not as of the same substance with the Father, but of a substance like in all things except in not being the Father's substance. They maintained, at the same time, that though the Son and Spirit were separated in substance from the Father, still they were so included in his glory that there was but one God. Unlike the Arians, they declared that our blessed Lord was not a creature, but truly the Son born of the substance of the Father; yet they would not allow him, with the orthodox, simply to be God as the Father was, but asserted that the Son, though distinct in substance from God, was at the same time essentially distinct from every created nature.
The Semi-Arian party first came into prominence at the Council of Nicaea (A.D. 325), under the leadership of Eusebius, bishop of Caesarea. During the fifty-six years that elapsed between the Council of Nicaea and that of Constantinople (A.D. 325-381) as many as eighty councils are on record, a large number of which were held by the Semi-Arian bishops in support of their contests with the orthodox and with their own sects. The Semi-Arian party had not one uniform definition of faith, but differed from each other on many important points; the only real bond of union was their opposition to the term which unequivocally expressed Catholic doctrine. Nothing, in fact, was more conspicuous than the unsettled variableness of the Semi- Arian creed. Two confessions of faith were drawn up at the Council of the Dedication (Socrates, Hist. Eccl. 2, 10), held at Antioch, A.D. 341; another by the bishops of Palestine, a few months afterwards (ibid. 2, 18); four years later (A.D. 345) at Antioch; at Sirmium (A.D. 351 [see Sozomen, Hist. Eccl. 4, 6]); and again at the same place seven years later (ibid.). From about this time a reaction went steadily on, until in A.D. 366
fifty-nine Semi-Arian bishops subscribed an orthodox formula, and were received into the Catholic Church (Socrates, Hist. Eccl. 4, 12). There is no evidence of any large number of the party afterwards existing. Many others, doubtless, came back to the Church, not a few plunged into the heresy of the Macedonians, SEE MACEDONIUS, and some, like Eudoxius of Antioch, became avowed Anomoeans. Consult Blunt, Dict. of Theology; id. Dict. of Sects, s.v.; Hagenbach, Hist. of Doctrines, vol. 1, § 92; Newman, Hist. of the Arians; Pusey, Councils of the Church, ch. 5. Gardner, Faiths of the World, s.v. SEE ARIANISM; SEE SABELLIUS.