What Happened at the Council of Nicaea?

Novels and internet rumors credit this council with picking the books of the Bible. The real history is more interesting: a fight over whether Jesus was truly God, settled in a creed Christians still recite.

Why the emperor called a council

In AD 325, the Roman Emperor Constantine, who had legalised Christianity only twelve years earlier, summoned bishops from across the empire to the city of Nicaea (modern İznik, Turkey). He wanted the church settled and unified — not out of theological conviction but because a fractured church threatened a fractured empire. Somewhere between 250 and 300 bishops attended; tradition rounds the number to 318, making it the first council to claim the whole church, not just one region, as its audience.

The dispute: was the Son equal to the Father?

The trigger was a priest in Alexandria named Arius. He taught that the Son — Christ, God's Word — was the first and greatest of God's creations, but not eternal and not equal to the Father: “there was a time when he was not,” in Arius's own phrase. Alexandria's own bishop condemned the teaching, but it spread fast enough that Constantine felt he had to intervene.

Arius could point to real texts. Paul calls Christ “the firstborn of every creature” — read one way, that sounds like Christ had a beginning.

Nicaea's bishops read it differently: “firstborn” as supremacy and inheritance, not birth order — the same sentence goes on to say “by him were all things created” and “he is before all things,” language that puts Christ on the creating side of that line, not the created side. John's opening had already said as much.

What the council produced: the Nicene Creed

The bishops answered with a creed — a short, memorised statement of belief — declaring the Son “begotten, not made, of one substance (homoousios in Greek) with the Father.” That one word, homoousios, “same substance,” was the council's real achievement: a technical term borrowed from Greek philosophy to close the loophole Arius's language left open. The creed was revised and expanded at a second council, in Constantinople in 381, into the form most churches still recite today as the Nicene Creed.

What else the council did

Nicaea also settled a running dispute over when to celebrate Easter (fixing it to a Sunday, independent of the Jewish Passover calendar different regions had been following) and issued twenty church-discipline rules — how bishops are chosen, what to do with clergy who had lapsed under persecution, and similar administrative matters. None of this touched what belongs in the Bible.

The myth: did Nicaea decide the Bible's books?

No. This is the single most common misconception about the council, popularised by novels like The Da Vinci Code, and nothing in the council's own surviving records supports it. The twenty canons Nicaea actually passed are preserved and say nothing about scripture's contents. The New Testament's list of 27 books was never voted on at any single meeting; it took shape gradually over the following century through the separate, slower process described in the companion article below.

Arianism didn't disappear overnight

Nicaea settled the question on paper, not in practice. Constantine himself later favoured Arian-leaning bishops, several Germanic peoples who came to Christianity in the following century did so through Arian missionaries, and the argument dragged on for decades before Nicene Christianity became the empire's settled default.