St. Athanasius of Alexandria (298-373), Confessor and Doctor of the Church, was one of the principal architects of the Nicene Creed. He persisted throughout his life, in and out of persecution, in explaining and defending Christ's divinity and the teachings of the Nicene Council.

In his Defense of the Nicene Definition, Athanasius defends the specific doctrine of the Council of Nicaea that the Father and the Son are "one in substance." Responding to Arian efforts to show from Scripture that Christ is a created being, Athanasius examines the witness of Isaiah and the Gospels,...