The First Council of Nicaea was a theological conference convened by Emperor Constantine the Great in 325 CE to address major divisive issues within the Church and restore religious peace in the Roman Empire. It was the first conference to bring together bishops from the entire known world of Christianity at the time.

A popular misconception about the First Council (repeated by writers from Voltaire to Dan Brown) was that it decided which books of the Bible were canon and which weren’t. The canonization of the New Testament was actually a centuries-long process of debate and analysis — it was not confirmed at a single meeting.

One of the main issues the Council did address was Arianism, a doctrine espoused by a priest named Arius of Alexandria. Arianism held that Jesus the Son was not eternal in nature because he was born from (and therefore after) God the Father, an idea that many other bishops found heretical.

Despite the label of heresy, Arius and his teachings were very popular in both the Eastern and Western halves of the Roman Empire. The First Council was not even the first attempt to stop him; a bishop had previously driven him out of Egypt, only for him to gain more followers in Palestine.

One famous story about the First Council claims that St. Nicholas of Myra (the inspiration for Santa Claus) was present at the meeting and that he punched Arius in the face for heresy. However, it is certainly not true — not all accounts list St. Nicholas as an attendee, and the original story first appeared 1000 years after the meeting.