Early in the fourth century the Alexandrian priest Arius launched a doctrine that would sunder the church. God's son cannot be God, he reasoned, but only a sublime creation. From the same city rose Athanasius in reply: Christ had two natures, one human, one divine, else how could he intercede between eternal God and temporal man? (317:3)
Bishop Gregory of Nazianzus joined the fray: his preachings against the Arians won him the title "the Theologian." From Antioch rang the eloquence of John Chrysostom, the "Golden-mouthed"; applause punctuated his anti-Arian sermons. As the great fathers defined the Son of God they laid firm footings for the coming definition of the third in the Trinity, the Holy Spirit. (317:4)
"O... what a wound did my ears receive," sighed Constantine over the Arian "squabbles." Calling the heresy "unworthy of men of sense," he ordered bishops to Nicea in 325; when they damned Arianism, he put teeth in the verdict by exiling its leaders. But his successor recalled them and banished their foes. As the battle seesawed, Athanasius trudged into five exiles totalling nearly 20 years. Though Arianism had died in the East by the end of the fourth century, it lingered into the seventh among Germanic tribes as the faith spread westward. (317:5)
Thus exiling replaced mere shunning of heretics. The in 386 the Spanish heretic Priscillian was executed; this ominous precedent would echo in horrors such as inquisitions and internecine wars. Indeed, Christians down through the ages slew more Christians than ever the Romans had martyred.