In the 4th-century, a group of Christians led by a fellow named Arius, a priest of the city of Alexandria (Egypt), argued that Christ was not God, but a superior being created by the Father. This led to an event called the “Arian controversy,” which would be the catalyst for the creation of what we today call orthodox Christian doctrine—beliefs that are true, established and approved by the universal Church.
The defining event of the Arian controversy was the Council of Nicea (325 A.D.), from where we get the Nicene Creed. The major opponents of Arianism were Alexander of Alexandria and Athanasius of Alexandria.
Athanasius argued that the doctrine of salvation was dependent upon the incarnation and full divinity of the Word; only God could save humanity, a task no mere creature was able to accomplish. Furthermore, if Christ was a created being that meant Christians were worshiping a creature. This put them into the category of pagan idol worship and meant the Church had been in serious error for three whole centuries. To Athanasius, this was highly unlikely. It was Arius who was mistaken, not Alexander or himself. Athanasius writes:
He put on the creature, that He as creator might once more consecrate it, and be able to recover it. But a creature could never be saved by a creature, any more than the creatures were created by a creature, if the Word was not creator. Accordingly let them not lie against the divine Scriptures nor give offense to simple brethren; but if they are willing let them change their mind in their turn, and no longer worship the creature instead of God.
Through their firm stance against Arian heresy, Alexander and Athanasius paved the way for what we call today Nicene orthodoxy—that Jesus is fully human and fully God.
This event led to the formulation of the Nicene Creed. Included in this Creed are five anti-Arian clauses that deserve mentioning:
First, the phrase that Christ is “God of God, light of light, true God of true God” declares the Word coequal with the Father and affirms the incarnation.
Second, by declaring that the Son is “begotten, not made,” the Creed affirms that the Son is not a created being, but coeternal with the Father.
Third, at the end of the Creed it is declared that any person holding to Arian beliefs (e.g. “that there was when He was not”, “that the Son of God is of a different substance or essence” than the Father, “that He is created, or mutable” ) was condemned by the Church.
Finally, one last important rejection of Arian theology would prove to be a substantial contribution in shaping Christian doctrine. Arians, believing the Son to be a superior being created by the Father, suggested the Creed should say that He was “of similar substance” as the Father. Although some at the council seemed ready to accept this wording, Athanasius, was not. Convinced that the Church’s foundation and future rested upon a clear conviction that Jesus could only be “of the same substance” as the Father (not just “of similar substance), He swung a majority of the council to reject Arianism.
If it were not for the threat of Arianism in the 4th-century, the Church today would not have the sound theology that has grounded it over the centuries. The rejection of Arian heresy shaped how Christians view Christ in light of salvation. Without a fully divine Saviour, there could be no salvation for human souls. This is why Nicene orthodoxy was the most important cause in the history of the Church and why we owe our belief that the infant Jesus is God to 4th-century theologians.