First Council of Constantinople

Section I

The Crisis that summoned First Council of Constantinople

The apologetic argument: The Council of Constantinople I completes the Trinitarian definition begun at Nicaea. The Holy Spirit is fully God — not a creature, not a divine energy, but the third Person of the Trinity, proceeding from the Father, co-worshipped and co-glorified with the Father and Son. This definition was made by the Church's teaching authority using categories not explicitly found in Scripture — another permanent refutation of Sola Scriptura.

The First Council of Constantinople was convened by Emperor Theodosius I in AD 381. Its immediate purpose was to end the Arian crisis that had continued to convulse the Eastern Church despite the definitions of Nicaea. The Council reaffirmed Nicaea, condemned Arianism and all its variants, and — crucially — extended the Nicene definition to include the full divinity of the Holy Spirit.

The Macedonians (also called Pneumatomachi — “fighters against the Spirit”) had accepted the Son’s full divinity but denied it to the Spirit, describing the Holy Spirit as a creature or a divine energy rather than a divine person. The Council condemned this and implicitly defined the Spirit as homoousios with the Father and Son — though it used the phrase who proceeds from the Father rather than the full homoousios formula.

The Council also produced what we now call the Nicene Creed — strictly the Nicene-Constantinopolitan Creed — which expanded the original Nicene text to include the fuller pneumatology. This is the creed recited at Sunday Mass in the Catholic Church to this day.

Section II

The Creed Defined

Defined at First Council of Constantinople

We believe in one God, the Father Almighty, maker of heaven and earth, of all things visible and invisible.

And in one Lord Jesus Christ, the only-begotten Son of God, begotten from the Father before all ages, Light from Light, true God from true God, begotten not made, of one substance (homoousios) with the Father, through Whom all things were made; Who for us men and for our salvation came down from heaven, and was incarnate from the Holy Spirit and the Virgin Mary and became man; and was crucified also for us under Pontius Pilate, and suffered and was buried; and rose again on the third day according to the Scriptures, and ascended into heaven and sits on the right hand of the Father; and will come again with glory to judge living and dead, of Whose kingdom there will be no end.

And in the Holy Spirit, the Lord and life-giver, Who proceeds from the Father, Who together with the Father and Son is worshipped and glorified, Who spoke through the prophets; in one holy, catholic and apostolic Church. We confess one baptism for the forgiveness of sins. We await the resurrection of the dead and the life of the age to come. Amen.

Section III

Key Canons

Click any canon to expand the full text, commentary, and apologetic significance.

Canon 1

Confirmation of Nicene Faith

Doctrine

The faith of the 318 Fathers assembled at Nicaea in Bithynia shall not be set aside, but shall remain dominant. And every heresy shall be anathematized.

The Council reaffirms Nicaea as the permanent, irreformable standard of Trinitarian orthodoxy. Arianism in all its forms — Eunomianism, Macedonianism, Pneumatomachism — is condemned.

Apologetic Significance The permanent authority of Nicaea is confirmed by a second ecumenical council — establishing the principle that ecumenical definitions are irreversible.

Canon 3

Honour of Constantinople After Rome

Precedence

The Bishop of Constantinople, however, shall have the prerogative of honour after the Bishop of Rome, because Constantinople is new Rome.

This canon establishes the order of patriarchal honour: Rome first, Constantinople second. It is sometimes cited against Roman primacy — but it confirms it: you cannot place Constantinople after Rome without placing Rome first.

Apologetic Significance Even a canon designed to elevate Constantinople confirms Rome's first place. The Eastern Church's own conciliar legislation acknowledges Roman primacy.

Section IV