The answer
The Creed was instituted over two stages, corresponding with the appearance of heresies, against which the Christian Church had to defend Her Faith.
First:
In A.D. 325, the First Ecumenical Council was convened in the City of Nicaea in Turkey to deliberate over the heresy of Arius the Heretic, who attempted to sway the established Faith of the Church by saying that Christ is not eternal, and therefore not God, but merely a mediator between God and men.
In response to this heresy, the Council formulated the first part of the Creed (from its beginning to “Yes, we believe in the Holy Spirit”).
Second:
In A.D. 381, the Second Ecumenical Council was convened in the City of Constantinople (now Istanbul, Turkey) to deliberate over the heresy of Macedonius the Heretic, who taught that the Holy Spirit is not God.
In response to this heresy, the Council completed the second part of the Creed, demonstrating and dividing4 our belief in the Holy Spirit and His Divinity (the Lord, the Giver of Life...and the life of the coming age. Amen.).
His Holiness Pope Tawadros II
Notes
4 Translator’s note: Making or drawing distinction (discerning) between what is sound and what is not.
Pope Tawadros II, My Faith: A Series of Dialogues on the Creed (Coptic Orthodox Patriarchate, 2014), 13–14.
The pages in the book (13–14)
