Arianism

Arianism is a nontrinitarian belief that asserts that Jesus Christ is the Son of God, created by God the Father, distinct from the Father and therefore subordinate to the Father. Arian teachings were first attributed to Arius (c. AD 250–336), a Christian presbyter in Alexandria, Egypt. The teachings are opposed to mainstream Christian teachings on the nature of the Trinity and on the nature of Christ. The Arian concept of Christ is that the Son of God did not always exist, but was created by God the Father. This belief is based on an interpretation of a verse in the Gospel of John (14:28): "You heard me say, 'I am going away, and I am coming back to you.' If you loved me, you would be glad that I am going to the Father, for the Father is greater than I."

Trinitarianism was formally affirmed by the first two Ecumenical Councils. All mainstream branches of Christianity therefore consider Arianism to be heterodox and heretical. The Ecumenical First Council of Nicaea of 325 deemed it to be a heresy. At the regional First Synod of Tyre in 335, Arius was exonerated. After his death, he was again anathemised and pronounced a heretic again at the Ecumenical First Council of Constantinople of 381. The Roman Emperors Constantius II (337–361) and Valens (364–378) were Arians or Semi-Arians.