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451
Anno Domini

Ecumenical Council

Council of Chalcedon

The Fourth Ecumenical Council — defined the two natures of Christ, fully human and fully divine, in one divine person. The most philosophically precise of the ecumenical Christological definitions, and the one most contested in the East.

October–November AD 451 Chalcedon, Bithynia (modern Kadıköy, Istanbul) Convoked by: Emperor Marcian and Empress Pulcheria c. 520 (largest early council) bishops 30 canons
Ecumenical Council — Universally Recognised
30Canons
5Key Figures
Section I

The Crisis that summoned Council of Chalcedon

The apologetic argument: When Pope Leo's Tome was read at Chalcedon, the bishops responded: Peter has spoken through Leo. This is the most dramatic conciliar confirmation of Petrine authority in all of patristic history — 500 Eastern bishops, convened by an Eastern emperor, acknowledging that the Bishop of Rome had spoken with apostolic authority on behalf of the Apostle Peter.

The Council of Chalcedon was convened by Emperor Marcian in October AD 451 in the city of Chalcedon, across the Bosphorus from Constantinople. It was the largest of the early ecumenical councils, attended by over 500 bishops — almost entirely Eastern. Its purpose was to correct the opposite error from Nestorianism: Eutychianism, which so emphasised the unity of Christ’s person that it merged his two natures into one.

Eutyches, an elderly monk of Constantinople, had been teaching that Christ’s humanity was absorbed into his divinity at the Incarnation — that after the union there was only one nature. Pope Leo I had condemned this in his famous Tome, a letter of such theological precision that when it was read at the Council, the bishops responded: “Peter has spoken through Leo.” The Council confirmed Leo’s theology: Christ is one divine person in two complete natures — fully human and fully divine — without confusion, change, division, or separation.

The Chalcedonian Definition remains the Christological standard of the Catholic, Orthodox (with exceptions), Anglican, Lutheran, and Reformed churches. It is the most widely accepted doctrinal statement in Christian history after the Nicene Creed.

Section II

The Creed Defined

Defined at Council of Chalcedon
Following the holy Fathers we teach with one voice that the Son [of God] and our Lord Jesus Christ is to be confessed as one and the same [Person], that he is perfect in Godhead and perfect in manhood, truly God and truly man, of a reasonable soul and body consisting, consubstantial with the Father as touching his Godhead, and consubstantial with us as touching his manhood; made in all things like unto us, sin only excepted; begotten of his Father before the worlds according to his Godhead; but in these last days for us men and for our salvation born [into the world] of the Virgin Mary, the Mother of God according to his manhood.

This one and the same Jesus Christ, the only-begotten Son [of God] must be confessed to be in two natures, unconfusedly, immutably, indivisibly, inseparably [united], and that without the distinction of natures being taken away by such union, but rather the peculiar property of each nature being preserved and being united in one Person and one subsistence, not separated or divided into two persons, but one and the same Son and only-begotten, God the Word, our Lord Jesus Christ.
Section III

Key Canons

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

Canon 28
Equal Honour for Constantinople After Rome
Precedence
Following in all things the decisions of the holy Fathers, and acknowledging the canon of the one hundred and fifty bishops assembled in the God-beloved [city] of Constantinople… we do determine and enact the same things respecting the privileges of the most holy Church of Constantinople, which is new Rome.
Canon 28 attempted to give Constantinople equal jurisdiction with Rome in the East. Pope Leo I refused to ratify this canon, insisting that ecclesiastical rank could not be determined by political geography. The canon was ultimately not implemented as intended.
Apologetic Significance Leo's rejection of Canon 28 is one of the most important exercises of papal authority in the patristic period — a pope overruling a specific canon of an ecumenical council on jurisdictional grounds.
Acclamation
Peter Has Spoken Through Leo
Petrine Primacy
After the reading of Pope Leo's Tome, the bishops responded: This is the faith of the Fathers! This is the faith of the Apostles! So we all believe, thus the orthodox believe. Anathema to him who does not thus believe! Peter has spoken thus through Leo!
The spontaneous acclamation of 500 Eastern bishops, identifying Leo's doctrinal letter with the voice of Peter. This is not a Roman source. It is 500 Eastern bishops saying that the Bishop of Rome speaks with Petrine authority.
Apologetic Significance The most dramatic patristic confirmation of Petrine primacy: an ecumenical council of Eastern bishops, convened by an Eastern emperor, declaring that Peter speaks through the Roman bishop.
Section IV

Key Figures

LG
Pope Leo I (the Great)
Bishop of Rome whose Tome provided the theological framework for the Chalcedonian definition. Refused to ratify Canon 28.
Papal Authority — Rome
Eu
Eutyches of Constantinople
Elderly monk whose theology — that Christ has only one nature after the Incarnation — was condemned as Monophysitism.
Condemned Heretic
Di
Dioscorus of Alexandria
Archbishop of Alexandria who had protected Eutyches and presided over the Robber Council of 449. Condemned and deposed at Chalcedon.
Condemned — Deposed
Mr
Emperor Marcian
Convoked the Council and enforced its decisions. Accepted Chalcedon as the settlement of the Christological controversy.
Imperial Authority
An
Anatolius of Constantinople
Archbishop of Constantinople who proposed Canon 28 elevating Constantinople — which Leo I refused to ratify.
Catholic — Partially Opposed to Rome
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