First Council of Nicaea

The Council of Nicaea was the first council in the history of the Christian church that was intended to address the entire body of believers. It was convened by the emperor Constantine to resolve the controversy of Arianism, a doctrine that held that Christ was not divine but was a created being. The council deemed Arianism a heresy and enshrined the divinity of Christ by invoking the term homoousios (Greek: “of one substance”) in a statement of faith known as the Creed of Nicaea.

Not remotely. Arianism was actually the official orthodoxy of the Eastern Roman Empire until 381, when the Council of Constantinople declared the doctrine of the Trinity—that the Father, the Son, and the Holy Spirit are three equal parts of the single Godhead.

Constantine viewed conflict within the early Christian church as a tool of Satan and saw it as his duty to heal schisms wherever they appeared. His first attempt to do so was at the Council of Arles, which he convened in 314 to address the Donatist controversy in the Western Roman Empire. He saw the Arian heresy as a trivial disagreement between academics who had too much time on their hands, and he believed that the issues could be resolved at Nicaea without difficulty. He was mistaken.

The council failed to agree on a uniform date for Easter and, because of the objection of some delegates, did not adopt a policy on the celibacy of clergy. Although church teachings emphasized the importance of clerical celibacy, many priests and even some bishops had wives as late as the 10th century. Clerical marriage would not be formally abolished until the first and second Lateran Councils in the 12th century.