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.
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.
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.
In 355 Valens and Ursacius obtained the exile of the Western confessors Eusebius, Lucifer of Cagliari, Hilary of Poitiers, and Liberius followed.
In the Lent of 358, Basil, along with many bishops, was holding the dedicatory feast of a new church he had built at Ancyra when he received a letter from George of Laodicea, relating how Eudoxius had approved of Aëtius, and begging Macedonius of Constantinople, Basil, and the rest of the assembled bishops to decree the expulsion of Eudoxius and his followers from Antioch, else that great see were lost.
In consequence, the Synod of Ancyra published a long reply addressed to George and the other bishops of Phoenicia in which they recite the Creed of Antioch (341), adding explanations against the "unlikeness" of the Son to the Father taught by the Arians and Anomoeans, (from anomoios), and showing that the very name of father implies a son of like substance (homoiousios, or homoios kat ousian) Anathematisms are appended in which Anomoeanism is explicitly condemned and the teaching of "likeness of substance" enforced.
Legates were dispatched to the Council at Sirmium: Basil, Eustathius of Sebaste, an ascetic of no dogmatic principles, Eleusius of Cyzicus, a follower of Macedonius, and the priest Leontius, one of the emperor's chaplains.
They arrived just in time, for the emperor had been lending his ear to a Eudoxian, but he now veered round, issuing a letter (Sozomen, IV, xiv) declaring the Son to be "like in substance" to the Father, and condemning the Arians of Antioch.
Basil persuaded Constantius to summon a general council, Ancyra being proposed, then Nicomedia (both in Asia Minor), but as the latter city was destroyed by an earthquake, Basil was again at Sirmium in 359 where the Arianizers had meanwhile regained their footing; with Germinius of Sirmium, George of Alexandria, Ursacius and Valens, and bishop (later saint) Marcus of Arethusa, he held a conference which lasted until night.
At Seleucia, in 359, the Semi–Arians were in a majority, being supported by such men as St. Cyril of Jerusalem, his friend Silvanus of Tarsus and even Hilary of Poitiers, but they were unable to obtain their ends.
Basil, Silvanus and Eleusius, therefore, went as envoys to Constantinople, where a council was held in 360, which followed Rimini in condemning homoiousios together with homoousios and allowed homoios alone, without addition.
Macedonius organized a party which confessed the Son to be kata panta homoios, while it declared the Holy Ghost to be the minister and servant of the Father and a creature.