What were the particular occasions for assembling the First and Second Ecumenical Councils, which defined the Creed?
The First Council was convened at the invitation of the Emperor Constantine, chiefly to settle the controversy caused by the teaching of Arius, a presbyter of Alexandria.
Arius taught that although Jesus Christ could be called “God” or “divine,” he was not eternal as the Father is eternal. “There was a time when he was not,” said the Arians, meaning that God the Father had created the Word in time, and that for unending ages past the Father had existed without his Only-Begotten Son.
This heresy was condemned by the 318 bishops, the “Holy Fathers”, assembled at Nicaea, a number in which the ancient writers delighted to see prefigured the 318 servants of Abraham (Gen 14:14). The language of the Creed specifically refutes Arius’ false teaching, and the Greek term homoousios (“of one essence”) was adopted to signify that the Son is uncreated, as the Father is uncreated, for, as St Athanasius explains, the Fathers were compelled to gather the sense of the Scriptures into this word precisely because the Arians twisted every merely scriptural phrase to their own meaning (St Athanasius, On the Decrees of the Council of Nicaea, 19–20; see Q033, Q095).
The Council of Nicaea also promulgated important canons for the good order of the Churches, for instance, the rule that “there may not be two bishops in the same city” (Nicaea I, canon 8; see Q070, Q071).
The Second Council confirmed the true doctrine concerning the Holy Spirit, especially against the teaching of Macedonius and the “Spirit-fighters” (pneumatomachoi), who denied the Spirit’s full divinity. This Council brought the Creed to its final form, teaching, according to the Scriptures and the apostolic Tradition, that the Holy Spirit is “the Lord, the Giver of life, who proceeds from the Father, who with the Father and the Son together is worshiped and glorified, who spoke by the Prophets.” The Fathers of this Council of Constantinople (381) thus confirmed the theology of St Basil the Great, whose treatise On the Holy Spirit had demonstrated from Scripture and from the Church’s doxology that the Spirit is to be glorified together with the Father and the Son (St Basil the Great, On the Holy Spirit, 10.24–26; 27.68; see Q017, Q024).
