Arianism is named for Arius, a teacher in the early fourth century AD. An important debate among early Christians was the subject of Christ’s deity. Was Jesus truly God in the flesh, or was Jesus a created being? Arius held that Jesus was created by God as the first act of creation, that Jesus was the crowning glory of all creation. Arianism is the view that Jesus is a created being with some divine attributes, but He is not eternal. Jesus, according to Arius, is inferior to the Father and possesses a different essence and nature from God. Also, there was a time when God was not the Father—namely, before the Son was created.
Semi-Arianism was a position adopted by some fourth-century Christians. Semi-Arianism somewhat softened the teachings of Arianism by admitting that the Son was “of a similar substance” (homoiousious) as the Father, while rejecting that He was “of the same substance” (homoousious). The importance of this debate concerns the nature of Jesus as well as the doctrine of the Trinity. Is Jesus eternal God? Are God the Father, God the Son, and God the Spirit all to be identified as the One God? The answers to these questions determine to whom we should pray and offer worship.
Semi-Arianism tried to take a middle-of-the-road position concerning Arianism, but it still failed to provide the proper biblical perspective on the nature of Jesus Christ. A “similar” essence is still a “different” essence. In the Bible, Jesus is presented as both fully human and fully divine. If He is fully divine, then He is also eternal and cannot be a created being of God the Father. Jesus’ nature is not simply “like” the Father’s; He shares the Father’s exact nature (John 10:30; Colossians 2:9).
Semi-Arianism is not a theologically sound compromise between Arius’s position and orthodoxy. On the issue of Jesus’ divinity, there is no true compromise. Either Jesus was created, or He was not; He is either God in the flesh, or He is not. The Council of Nicaea in AD 325 rejected both Arianism and Semi-Arianism as heresy.
In the decades after Nicaea, however, Semi-Arianism continued to thrive, having the support of most bishops and the Emperor Constantius II. The orthodox bishop Athanasius was forced into exile. It was not until after the Council of Constantinople in 381, which upheld the Nicene Creed, and the work of the Cappadocian Fathers that Arianism finally lost influence in the church. Today, Semi-Arianism lives on in the Mormon teaching that Jesus is an actual son of God the Father and is thus a created being.
John 1:18 says, “No one has ever seen God, but the one and only Son, who is himself God and is in closest relationship with the Father, has made him known.” This verse, with its plain statement that Christ “is himself God,” refutes the Arian view (that the Son is of a different substance from the Father) and the Semi-Arian view (that the Son is only “similar” in substance to the Father). The Son makes the Father known to us. If Semi-Arianism were true, then the Father would still be a mystery, because a Son who is unlike His Father would be unable to fully reveal the Father.