Roman Emperor Constantine was the first the adopt Christianity, but during his time the religion was still disorganized, if no longer underground. No clear agreement existed on anything, from the details of the divinity of Christ to his relationship with the Father. Was Jesus in actuality the son of God, or was it a metaphor, like the other “sons of God” in the bible? The meeting to work out those questions was given further urgency by Arius, a presbyter around modern-day Libya who taught some heretical views of Christianity.

On this day, May 20, in 325 A.D. the First Council of Nicea convened in Bythinia, in the Roman Empire (modern-day Iznik, Turkey) to establish some religious canon and combat Arianism over the nature of the Trinity.

Over three hundred bishops attended from nearly all the eastern provinces of the empire, where the Arian heresy was most rampant. The major result was the production of the Nicean Creed, which held that God the Father and Son were co-eternal (meaning both had existed forever) and co-substantial (meaning they are as one). The Nicean Creed also held that Arianism, which taught the Son was created by the Father, was heretical.