When at Alexandria, after Achillas who had succeeded Peter the Martyr, Alexander had taken up the office of bishop, since peace and quiet from persecutions were granted to our people, and the glory of the Churches rejoiced in the merits of the Confessors, the prosperity of our affairs was thrown into turmoil by domestic strife. For a certain presbyter at Alexandria, Arius by name, a man religious in outward appearance and form rather than in virtue, but wickedly greedy of glory, praise, and novelty, began to put forward certain corrupt notions concerning the faith of Christ, things which had never before come into question: he attempted to cut off and separate the Son from that eternal and ineffable substance, or nature, of God the Father. This matter threw very many in the Church into confusion.
But although Bishop Alexander, gentle and quiet by nature, desired by constant admonitions to recall Arius from his depraved undertaking and impious assertions, yet the matter did not proceed according to his wish, because the contagion of that pestilent assertion had already infected very many—and not only at Alexandria, but spread through other cities and provinces as well. Believing it would be ruinous if he were to conceal such things, he disclosed the matter to very many of his fellow-bishops. The controversy became more widely known. The report reached even to the ears of the religious emperor, who indeed cared with all zeal and diligence for those things which are ours.
Then, by the counsel of the bishops, he convened an episcopal council at the city of Nicaea (in the year 325), and there commanded Arius to appear before three hundred and eighteen bishops in session, and that judgment be passed upon his propositions and questions.