Semi-Arianism

Semi-Arianism was a position regarding the relationship between God the Father and the Son of God, adopted by some 4th-century Christians. Though the doctrine modified the teachings of Arianism, it still rejected the doctrine that Father, Son, and Holy Spirit are co-eternal, and of the same substance, or consubstantial, and was therefore considered to be heretical by many contemporary Christians.

Arius held that the Father, Son, and Holy Spirit were three separate essences or substances (ousia) and that the Son and Spirit derived their divinity from the Father, were created, and were inferior to the Godhead of the Father. Semi-Arians asserted that the Son was "of a similar substance" (homoiousios) as the Father but not "of the same substance" (homoousios).

Arianism was the view of Arius and his followers, the Arians, that Jesus was subordinate to, and of a different being (ousia) to God the Father. Arians opposed the view that the three persons of the Trinity were of one being or substance. Arianism spread among the Church of Alexandria and the Eastern Mediterranean. After the First Council of Nicaea condemned Arianism as heresy, many Christians adopted compromise views in which they remained in communion with Arians without adopting Arianism itself. Various formulae, such as the homoiousian and the homoean, were proposed to compromise between Arian teachings (heteroousios) and the doctrine of one substance (homoousios) asserted in the Nicene Creed.

After the 325 Council of Nicea anathemized Arianism: the majority of the Eastern bishops, who agreed to the deposition of Athanasius of Alexandria at Tyre in 335 and received the Arians to communion at Jerusalem on their repentance, were not Arians. The Dedication Council of Antioch in 341 put forth a creed which was unexceptionable but for its omission of the Nicene formula "of One Substance." Even disciples of Arius such as bishop George of Laodicea (335–47) and Eustathius of Sebaste (c. 356–80) joined the moderate party, and after the death of Eusebius of Nicomedia, the leaders of the court faction, Ursacius of Singidunum, Valens of Mursa and Germinius of Sirmium, were not tied to any formula, for Emperor Constantius II himself hated Arianism, though he disliked Athanasius yet more. When Marcellus of Ancyra was deposed in 336, he was succeeded by Basil. Marcellus was reinstated by the Council of Serdica and bishop Julius of Rome in 343, but Basil was restored in 350 by Constantius, over whom he gained considerable influence. He was the leader of a council at Sirmium in 351, held against Photinus who had been a deacon at Ancyra, and the canons of this synod begin by condemning Arianism, though they do not quite come up to the Nicene standard. Basil had afterwards a disputation with the Anomoean Aëtius.

After the defeat of Magnentius at Mursa in 351, Valens, bishop of that city, became the spiritual director of Constantius. In 355 Valens and Ursacius obtained the exile of the Western confessors Eusebius, Lucifer of Cagliari, Hilary of Poitiers, and Liberius followed. In 357 they issued the second Creed of Sirmium, or "formula of Hosius", in which homoousios and homoiousios were both absent. Eudoxius seized the See of Antioch, and supported Aëtius and his disciple Eunomius.

The Third Council of Sirmium in 357 was the high point of Arianism. The Seventh Arian Confession (Second Sirmium Confession) held that both homoousios (of one substance) and homoiousios (of similar substance) were unbiblical and that the Father is greater than the Son. (This confession was later known as the Blasphemy of Sirmium.)

But since many persons are disturbed by questions concerning what is called in Latin substantia, but in Greek ousia, that is, to make it understood more exactly, as to 'coessential,' or what is called, 'like-in-essence,' there ought to be no mention of any of these at all, nor exposition of them in the Church, for this reason and for this consideration, that in divine Scripture nothing is written about them, and that they are above men's knowledge and above men's understanding;

It has been noted also that the Greek term "homoousian", which Athanasius of Alexandria favored, was actually a term that was reported to be put forth and favored also by Sabellius, and was a term that many followers of Athanasius took issue with and were uneasy about. The Semi-Arians also objected to the term. Their objection to the term "homoousian" was that it was considered to be "un-Scriptural, suspicious, and of a Sabellian tendency." This was because Sabellius also considered the Father and the Son to be "one substance", meaning that, to Sabellius, the Father and Son were "one essential Person" interacting with creation as necessary.