In those same years Alexandria saw the rise of the most challenging heresy in the history of the Church. About 318 a priest from the Egyptian town of Baucalis startled his bishop with strange opinions about the nature of Christ. A learned Catholic historian describes him generously:

Arius… was tall and thin, of melancholy look, and an aspect that showed traces of his austerities. He was known to be an ascetic, as could be seen from his costume- a short tunic without sleeves, under a scarf that served as a cloak. His manner of speaking was gentle; his addresses were persuasive. The consecrated virgins, who were numerous in Alexandria, held him in great esteem; and he counted many stanch supporters among the higher clergy.

Christ, said Arius, was not one with the Creator, he was rather the Logos, the first and highest of all created beings. Bishop Alexander protested, Arius persisted. If, he argued, the Son had been begotten of the Father, it must have been in time; the Son therefore could not be coeternal with the Father. Furthermore, if Christ was created, it must have been from nothing, not from the Father’s substance; Christ was not “consubstantial” with the Father. The Holy Spirit was begotten by the Logos, and was still less God than the Logos. We see in these doctrines the continuity of ideas from Plato through the Stoics, Philo, Plotinus, and Origen to Arius; Platonism, which had so deeply influenced Christian theology, was now in conflict with the Church. Bishop Alexander was shocked not only by these views but by their rapid spread even among the clergy. He called a council of Egyptian bishops at Alexandria, persuaded it to unfrock Arius and his followers, and sent an account of the proceedings to other bishops. Some of these objected; many priests sympathized with Arius; throughout the Asiatic provinces clergy as well as laity divided on the issue, and made the cities ring with such “tumult and disorder… that the Christian religion,” says Eusebius, “afforded a subject of profane merriment to the pagans, even in their theaters.” Constantine, coming to Nicomedia after overthrowing Licinius, heard the story from its bishop. He sent both Alexander and Arius a personal appeal to imitate the calm of philosophers, to reconcile their differences peaceably, or at least to keep their debates from the public ear. The letter, preserved by Eusebius, clearly reveals Constantine’s lack of theology, and the political purpose of his religious policy.

I had proposed to lead back to a single form the ideas which all people conceive of the Deity; for I feel strongly that if I could induce men to unite on that subject, the conduct of public affairs would be considerably eased. But alas! I hear that there are more disputes among you than recently in Africa. The cause seems to be quite trifling, and unworthy of such fierce contests. You, Alexander, wished to know what your priests were thinking on a point of law, even on a portion only of a question in itself entirely devoid of importance; and you, Arius, if you had such thoughts, should have kept silence…. There was no need to make these questions public… since they are problems that idleness alone raises, and whose only use is to sharpen men’s wits… these are silly actions worthy of inexperienced children, and not of priests or reasonable man.