Arianism

The heresy propagated by Arius denying the Divinity of Jesus Christ. Following views which Gnostics had popularized, he regarded the Son of God as standing midway between God and creatures; not like God without a beginning, but possessing all other Divine perfections, not of one essence, nature, substance with the Father and therefore not like him in Divinity; an attribute of the Divine nature, the Logos, or Word, Reason. The heresy for a time threatened to rend asunder the Catholic Church, especially when favored by the emperors of the East. It was the root source of many heresies. Its antagonist Athanasius contended for half a century for the term consubstantial (Greek: Homoousion, one and the same, as against Homoiousion, like only) to express the identity of the Son in essence, nature, substance with the Father, which was adopted at the Council of Nicaea in 325. This decision established the doctrine of the Divinity of Christ, and although it did not end the struggle of the Arians for ascendancy, it defeated their efforts to anticipate Mohammed and to introduce Unitarianism as Catholic belief.