The Council of Chalcedon (AD 451)

Between AD 431 and 451, the Christian church tried to say what every Sunday School child can say in a sentence: Jesus is fully God and fully man. Getting those words to hold together, in Greek, in a way that could not be twisted into either “Jesus is two persons, a divine and a human” or “Jesus is one person with one blended nature that is neither quite divine nor quite human,” took twenty years, four councils, the deposition of a patriarch, an emperor’s widow, a pope’s intervention, a great deal of violence, and the permanent departure of roughly a third of the world’s Christians.

The document that came out of Chalcedon in October 451 is one of the three or four most important sentences in Christian history. Every orthodox Christology since — Catholic, Protestant, Eastern Orthodox — begins there. The Copts, Ethiopians, Armenians, Syriacs, and Indians who did not accept Chalcedon’s language have, for fifteen centuries, been confessing the same reality in different words. This is a lesson about what it means for the church to say, with precision, who Jesus Christ is.

Everything Chalcedon will say is a commentary on those thirteen Greek words.

After Nicaea (325) and Constantinople (381) had settled that the Son is homoousios with the Father, a new question came forward: given that the Son is truly God, what exactly happened when he became flesh? How is the divine Son related to the human Jesus who ate, wept, slept, and died? Five possible answers were on the table in the fifth century, and four of them were wrong:

The argument that produced Chalcedon was largely a collision between two theological traditions that had been growing apart for two centuries.

Both schools read the same Scriptures. Both accepted Nicaea. Both loved Christ. But their instincts about how to protect his identity were moving in opposite directions. Chalcedon’s triumph was to affirm what both schools were trying to protect and to rule out the extremes each produced.

The Council. Under pressure from Cyril and Pope Celestine of Rome, Emperor Theodosius II summoned a general council to Ephesus for Pentecost 431. The meeting was a diplomatic catastrophe: Cyril’s Alexandrian party arrived first, refused to wait for the Antiochene delegation, and on 22 June 431 met in the church of the Theotokos in Ephesus (already a Marian shrine). They read Nestorius’ teachings aloud and condemned him the same day. When John of Antioch and his Eastern bishops arrived four days later, they held a counter-council that deposed Cyril. For weeks the two councils sat in the same city excommunicating each other.

Theodosius eventually sided with Cyril. Nestorius was deposed, exiled first to a monastery near Antioch, then to the Great Oasis in Upper Egypt. He died there around 451, probably on the very eve of Chalcedon.

The Formula of Reunion (AD 433). Two years of diplomacy between Cyril and John of Antioch produced a compromise document that both sides could sign. It affirmed Theotokos; it affirmed the distinction of natures in Christ; it was one of the earliest attempts at what Chalcedon would later finalize. Ephesus was now the Third Ecumenical Council.

Cyril died in 444. His successor at Alexandria, Dioscorus, was a less subtle theologian and a more aggressive politician. In Constantinople an elderly archimandrite named Eutyches — a favorite of the imperial court — began to teach a position even more extreme than Cyril’s:

The Robber Council (Latrocinium) of Ephesus, August 449. Emperor Theodosius II, manipulated by the eunuch Chrysaphius and by Dioscorus, called another general council at Ephesus to try Eutyches. Dioscorus presided and ran it with brutality: he excluded Flavian of Constantinople (the orthodox patriarch), refused to read Pope Leo’s representative’s letter, and had soldiers physically assault bishops who resisted. Flavian was beaten so badly he died of his injuries days later.

Pope Leo I in Rome, when he heard the news, coined the phrase the church has used ever since: “latrocinium” — “a robber-meeting,” not a council. Leo refused to accept its decisions. A standoff now lay between Rome and Alexandria.

The accident that saved the church. On 28 July 450, Theodosius II fell from his horse while hunting and died. His pious sister Pulcheria — who had never accepted Eutyches’ teaching — married the general Marcian and put him on the throne. Pulcheria and Marcian summoned a new council to settle the matter properly. It would meet at Chalcedon, directly across the Bosphorus from Constantinople, in October 451.

Leo’s Tome. Before the council met, Pope Leo I sent a dogmatic letter to Flavian (originally written for the 449 council but never read there). This Tome of Leo is one of the greatest documents of Western theology, and the first major voice of the Latin church in a Greek Christological controversy. Leo wrote, without hedging:

The council. Chalcedon opened on 8 October 451 in the basilica of St. Euphemia, across the Bosphorus from the imperial palace. It is the largest council of Christian antiquity — approximately 520–600 bishops, overwhelmingly from the East, along with papal legates from Rome. Emperor Marcian and Empress Pulcheria attended in person. The council sat for sixteen sessions over three weeks.

Key actions:

The text adopted on 22 October 451 is not, strictly, a creed; Chalcedon appended it to the Nicene-Constantinopolitan Creed as a definition (horos) of how the creed’s Christology should be read. The key paragraph:

The four adverbs. The heart of the Definition is four Greek adverbs stating what the union of the two natures is and is not. They function as four fences around the mystery:

The first two adverbs rule out monophysitism: the natures do not blend or change; the humanity remains fully human, the divinity fully divine. The last two adverbs rule out Nestorianism: the natures are not separable; there is one Jesus, not a divine-and-human pair. Between these four fences, the mystery is left to mystery.

Not everyone accepted Chalcedon. Large swaths of Eastern Christianity — especially in Egypt, the Syriac-speaking lands, Armenia, and Ethiopia — rejected the new Definition. Their argument was not that they held Eutyches’ position; they explicitly condemned it. Their argument was that Chalcedon’s language of “in two natures” sounded too Nestorian to them. They preferred Cyril’s formula: “one nature of the Word enfleshed” (mia physis). They are now called the Oriental Orthodox churches, and they are not monophysite in the Eutychian sense. The modern scholarly term for their view is miaphysite — emphasising that “one nature” here does not mean a blended or reduced Christ, but the one incarnate nature of the divine Logos.

These are not small communions. Together they represent roughly 60–80 million Christians today. They trace their episcopates back to the Apostles through the same early centuries as the Chalcedonian churches. They use essentially the Nicene Creed, the Eucharist, the sacraments, and the liturgical calendar that all classical Christians do. They simply do not say “in two natures” about Christ. They say, with Cyril, “one incarnate nature of the Word of God.”

Noll’s chapter on Chalcedon is titled Doctrine, Politics, and Life in the Word. He argues that Chalcedon is a turning point on three distinct levels:

Noll also notes, with some tenderness, that Chalcedon is the first council we can see both as the triumph of the church’s deepest instincts and as the cost of its willingness to be precise. Precision unites some and divides others. That is the permanent condition of Christian theology after 451.