Story
The road to Nicaea
From a local quarrel in Alexandria to an imperial council, without pretending the creed ended the fight.
Step 1
A presbyter and his bishop
Arius, a presbyter in Alexandria, taught that the Son is not eternal in the Father's own way. Bishop Alexander excommunicated him. The slogan 'there was when he was not' is how opponents summed Arius up. His own hymn, the Thalia, survives only in scraps.
Step 2
Constantine wants one church
After 324 Constantine ruled the whole empire and treated a divided church as a public problem. Ossius of Corduba carried his inquiries. This was pastoral politics as well as theology.
Step 3
The council of 325
Bishops at Nicaea adopted a creed calling the Son homoousios, 'of the same substance,' and condemned Arius. Easter's date and twenty canons were also settled. Who presided is not certain. The signed creed is the shorter 325 text, not the later liturgical creed.
Step 4
Nicaea did not end the argument
Within a decade Athanasius was exiled, Arius was nearly restored, and eastern councils offered other creeds. Calling every opponent 'Arian' hides real differences among them. The pro-Nicene settlement that lasted was the work of the 360s–380s, not of 325 alone.