What was decided at Nicaea?

The dispute at the centre of it was Arius’ teaching about the relationship between the Father and the Son. Neither side held that Jesus was an ordinary man. In the confession he later gave Constantine, Arius called the Son "God the Word". Alexander of Alexandria, who condemned him, wrote that his party held the Word "was made out of nothing".

The creed the council issued settles it with a phrase and a word: the Son is "of the substance of the Father", "begotten, not made", "of one substance" with the Father. The word is homoousios. The anathema attached to it condemns anyone who says "there was a time when the Son of God was not", or that he is of a different substance, or a creature, or subject to change.

Alongside the creed the council issued twenty canons, and they are largely about running an institution: who may be ordained, what clergy may not do with money, whether bishops and clergy may move between cities. Canon II is a rule against ordaining recent converts too quickly.

The council also settled when Easter should be kept. Its letter to Alexandria says that churches in the East "who formerly followed the custom of the Jews" would keep it "at the same time with the Romans". That was a practical problem rather than a metaphysical one, though Constantine’s own letter on the decision gives a reason as well as a date: "Let us then have nothing in common with the detestable Jewish crowd."

No canon of Nicaea lists the books of scripture, and nothing else the council issued that survives touches the subject. The earliest surviving list of exactly the twenty-seven New Testament books comes forty-two years later, in a bishop’s Easter letter, and even that letter was an attempt to close the list in one church rather than the end of the argument.

This is one of the things most often attributed to Nicaea, and the council’s own documents, with the earliest accounts of it, are the reason we can be confident it is wrong.

Constantine convened the council, provided transport, and pressed for a resolution. Eusebius of Caesarea, who was there, wrote home that the emperor urged the bishops to agree "with the insertion, however, of that single word homoousios". How much he shaped the outcome, and whether he cared about the theology or about an empire-wide church that agreed with itself, is hard to settle from a small set of sources, most of them written by people with a stake in the answer.

Nicaea was not the first time a Roman emperor had summoned bishops to settle a church dispute. Constantine had already called them to Arles in 314 over the Donatist quarrel in Africa, down to the offer of a place on the imperial post. Arles gathered the West; Nicaea was the first time it was done for the whole empire, and the arrangement outlasted him: the bishops who met at Constantinople in 381 came "on the summons of the most religious Emperor Theodosius".

Nicaea is often described as the moment orthodoxy was fixed. In practice the controversy ran for most of the following century: bishops on both sides were exiled and recalled as imperial favour moved, and Constantine himself recalled Arius and restored two of the bishops banished after the council. "Arian" as the name of one coherent party is largely a category its opponents built a generation later.

Historians differ on how to read that. One account has Nicaea stating a position that then had to be fought for. Another has the council’s formula being genuinely unclear at the time, and acquiring its settled meaning only through the decades of argument that followed.

There are no minutes. What survives is the output, plus later accounts by writers who were not neutral and in most cases were not present. The debates and the negotiations over wording are reconstructed from fragments and from what the final text seems designed to exclude.

The one part that is not obscure is that it was not close, though even the numbers differ. Eusebius, who was there, says the bishops "exceeded two hundred and fifty". Socrates, writing later, reports three hundred and eighteen subscribing and five holding out over one word, and the council’s own letter to Alexandria names two bishops condemned with Arius.

A creed is not a historical summary. The text of 325 was a test, subscribed by bishops and closed with anathemas against anyone who said otherwise. Said aloud by a congregation, a creed states what a community holds rather than recording what a meeting concluded.

The version the Catholic Catechism calls "common to all the great Churches of both East and West" is not quite the one issued in 325. It is the longer creed associated with the council at Constantinople in 381, which has the clauses about the Holy Spirit, the church and the resurrection that the text of 325 lacks. That text has the Spirit proceeding from the Father. The Western churches later added the words "and the Son", and the addition became one of the disagreements that separated East and West.

The popular version of Nicaea survives because it answers a real question, which is how a set of beliefs came to be the required ones. That is a fair question and the council is part of the answer.

Replacing a story with a document is not the same as replacing it with nothing. The documents show an institution consolidating, under imperial pressure, around a formula that a handful refused at the time and a sizeable party resisted for decades afterwards. That is interesting on its own terms and does not need improving.