First Council of Nicaea

A council of Christian bishops convened by Emperor Constantine at Nicaea in 325. It addressed the Arian controversy and produced the original Nicene Creed.

Arian controversy: A fourth-century dispute over whether the Son was eternal and equal to the Father or a created being. This dispute was the council’s central doctrinal issue.
Constantine the Great: Roman emperor from 306 to 337 who supported Christianity and convened the Council of Nicaea. He summoned the bishops and sought an empire-wide settlement.
Constantinople I: An ecumenical council held in 381 that reaffirmed Nicene theology and expanded the creed. It renewed Nicaea’s settlement and gave the creed its later form.
Arianism: A Christian theological position that holds the Son to be subordinate to the Father and not co-eternal with him. The creed rejected the view that the Son was a created being.
Nicene Creed: A Christian statement of faith first formulated at Nicaea in 325 and expanded at Constantinople in 381. The council’s creed used precise language to reject Arius’s account of the Son.
Alexander of Alexandria: Bishop of Alexandria whose dispute with Arius helped trigger the Arian controversy. His opposition to Arius brought the Alexandrian dispute to wider attention.
Athanasius of Alexandria: A bishop and theologian who defended Nicene theology and became a leading opponent of Arianism. His later career carried Nicene arguments through decades of conflict.
Homoiousianism: A fourth-century position that the Son was of similar substance to the Father, rather than the same substance. Its wording offered a rival formula to Nicaea’s homoousion.
Homoousion: A Greek theological term meaning “of the same substance,” used to describe the Son’s relation to the Father. The council adopted this contested term to affirm the Son’s full divinity.
Council of Antioch (325): A regional church council held in 325 that addressed disputes over doctrine and episcopal leadership. It preceded Nicaea and condemned positions associated with Arius.

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