Pope St. Leo the Great

The Doctor of Christian Unity

Pope St. Leo I (about 400 to 461) was the first pope to be called "the Great," a title later given also to Gregory I and Nicholas I. He reigned while the Western empire was coming apart: Vandals had taken North Africa and with it Rome's grain supply, Huns were moving into Italy, imperial authority in the West was collapsing into the hands of generals, and the bishop of Rome was steadily becoming the one figure in the city with continuity and standing.

Leo's work has two halves that belong together. He settled the Church's language about who Jesus Christ is, and he held Rome together through two invasions. Both were exercises of the same conviction, that the see of Peter carried a responsibility for the whole Church and for the city it sat in.

Who Leo Was, and the Rome He Governed

Leo was probably born in Tuscany around the year 400 and was raised in Rome. He first appears in the records as a deacon of the Roman church under Pope Celestine I and then under Sixtus III, and he was already influential enough that figures elsewhere in the empire wrote to him by name.

He was elected pope in an unusual way. He was in Gaul on an imperial mission, sent to reconcile two quarrelling Roman commanders, when Sixtus III died. The Roman clergy elected him in his absence and waited for him to come back. He was consecrated on 29 September 440 and governed for twenty-one years, dying on 10 November 461.

He is buried at St. Peter's in Rome, and his remains were moved inside the basilica in the seventh century.

Peter Has Spoken Through Leo

Leo's most significant theological contribution was his Tome, a letter written in June 449 to Flavian, the bishop of Constantinople, in a dispute about the person of Christ. In it he set out that Jesus Christ is one person in two natures, human and divine, distinct and not separated, each nature keeping what belongs to it and acting in communion with the other.

The dispute had a specific occasion. An elderly and influential monk in Constantinople named Eutyches taught that after the incarnation there was only one nature in Christ, and that his humanity was absorbed into his divinity like a drop in the ocean. Flavian held a local synod in 448 which condemned him. Eutyches appealed, and in 449 a council at Ephesus, dominated by Dioscorus of Alexandria, reinstated him and deposed Flavian, who died soon afterwards. Leo's legates were shouted down and his Tome was never read out. He called that assembly a latrocinium, a gang of robbers, and the name stuck to it.

Two years later the Emperor Marcian summoned a new council at Chalcedon, across the water from Constantinople, and it met in October 451 with several hundred bishops. There the Tome was read. According to the acts of the council the bishops acclaimed it: Peter has spoken through Leo. The council then issued its own Definition, which is the text the Catholic, Orthodox and most Protestant churches still use.

What the Tome Actually Says

The Tome is short and it can be read in twenty minutes. Its argument runs like this.

• Christ is one person, the eternal Son, who took a complete human nature into his own person without ceasing to be God.
• Both natures remain what they are. Divinity is not reduced and humanity is not swallowed. Each nature does what is proper to it in communion with the other, so that the Word does what belongs to the Word and the flesh does what belongs to the flesh.
• Because of this, the same person can be said to hunger, weep and die, and also to raise the dead and forgive sins. Leo lists the pairs deliberately.
• Salvation depends on it. If Christ is not truly God he cannot save, and if he is not truly man he has not saved what needed saving.

The Chalcedonian Definition took that up in the formula still quoted today: one and the same Christ, acknowledged in two natures, without confusion, without change, without division and without separation, the distinctive property of each nature preserved and concurring in one person. Those four negatives mark out the errors on both sides, and they are the reason the sentence is phrased as it is.

The Churches That Did Not Receive Chalcedon

Chalcedon settled the question for most of the Church and split off a large part of the East, and an honest page about Leo has to say so.

The churches now called Oriental Orthodox, the Coptic, Syriac, Armenian, Ethiopian, Eritrean and Malankara churches, did not accept the council. Their objection was to the phrase "in two natures," which they read as dividing Christ, and they confess instead one incarnate nature of the Word of God, understood as a union of full divinity and full humanity without confusion. They reject the label monophysite that Chalcedonian writers applied to them, and the term generally used now is miaphysite.

Modern dialogue has narrowed the gap considerably. Joint declarations signed between the Catholic Church and several Oriental Orthodox churches from the 1970s onward have stated that both sides confess the same faith in Christ, true God and true man, and that the historic disagreement was substantially about the language used. The separation of the communions remains. Our pages on the Oriental Orthodox churches and the Coptic Orthodox Church set out their position in their own terms.

There was a second dispute at Chalcedon that Leo lost. The council's twenty-eighth canon granted the see of Constantinople privileges second only to Rome, on the ground that it was the new imperial capital. Leo refused to confirm it, because he held that Rome's standing came from Peter rather than from imperial geography. Constantinople kept the canon. The argument about it ran for centuries and forms part of the background to the schism of 1054.

Turning Back the Huns

In 452 Attila the Hun invaded northern Italy, destroyed Aquileia and moved down the peninsula. There was no field army able to stop him. An embassy went out to meet him near the river Mincio, in the region of Mantua, and Leo was part of it, together with two senior imperial officials, the former consul Gennadius Avienus and the prefect Trygetius. After the meeting Attila turned his army around and left Italy.

The result is not disputed. The cause is. Contemporary and later historians point to plague and famine in the Italian countryside that year, to supply problems for a large army, and to Eastern Roman forces attacking Hunnic territory behind him. Leo's embassy was one factor among several, and Leo himself never claimed to have worked a wonder. The story that Attila saw St. Peter and St. Paul standing beside the pope with drawn swords appears in later accounts, and Raphael painted that version on a wall of the Vatican palace a thousand years afterwards. It is a legend attached to a real meeting.

Three years later the outcome was worse. In 455 Genseric and the Vandals came up from Africa and Rome had no defence. Leo went out to meet him too. The city was plundered for a fortnight, and the sources credit Leo with obtaining a promise that there would be no burning and no massacre. Rome lost its treasure and kept most of its people.

Leo also organised relief for the population afterwards, sent priests to Africa to care for the Romans carried off as captives, and kept the city's church functioning through both crises.

Leo and the Authority of Rome

Leo is the pope in whom the Roman claim becomes fully explicit. He taught that Peter continues to exercise his office through the bishop of Rome, that the pope is the unworthy heir who holds a place that belongs to Peter, and he applied that to practical governance: hearing appeals from bishops in Gaul, intervening in Spain against the Priscillianists, investigating Manichaean refugees who had come to Rome from Vandal Africa, and asserting Roman jurisdiction in Illyricum.

He is careful about the basis of the claim. In his sermons on the anniversary of his own consecration, he attributes everything to Peter and takes nothing to himself personally, which is why he can say that Peter has spoken while calling himself unworthy in the same paragraph. Our page on the papacy covers the doctrine and the historical development.

He was also strengthened by circumstances outside the Church. In 445 the Emperor Valentinian III issued a rescript supporting the primacy of the Roman see in the West. Leo used the standing that gave him, and the western bishops for the most part accepted it.

Sermons, Letters and What Survives

About ninety-six sermons and roughly a hundred and forty letters of Leo survive, which is a remarkable amount for a fifth-century pope and the reason he can be read rather than only described.

The sermons follow the liturgical year: Christmas, Epiphany, Lent, the Passion, Easter, Pentecost, and the feasts of Peter and Paul, along with sermons on the collection for the poor and on fasting. They are short, structured and unusually clear, and the Latin is famously polished. Passages from them are read in the Office of Readings throughout the year, so Leo is still preaching in the Church's daily prayer.

The letters are the working correspondence of a bishop with jurisdiction: rulings on the readmission of people baptised by heretics, on clergy discipline, on the date of Easter, on the conduct of councils, and the long exchanges around Chalcedon.

Feast Day, Doctor of the Church, Devotion

Before the calendar reform of 1969 his feast in the West was kept on 11 April; it was moved to 10 November, the day of his death. Eastern Orthodox and Byzantine Catholic churches honour him on 18 February, which is notable given the argument over canon 28: the East kept the pope who wrote the Tome.

Leo has no folk patronage of the kind attached to many saints, and this page will not invent one. He is invoked chiefly as a Doctor of the Church and a defender of the faith, and his tomb in St. Peter's Basilica is visited by pilgrims. Gregory the Great, the next pope to carry that title, governed a century and a half later.

Quotable Wisdom

"Christian, acknowledge your dignity, and becoming a partner in the Divine nature, refuse to return to the old baseness by degenerate conduct."

The line comes from his first Christmas sermon, and it is the practical point of the whole Christological argument. If God has taken a human nature, then human nature has been given a standing it did not have, and behaviour has to catch up with it. Leo preached that at Christmas rather than in a treatise, to a congregation, on the assumption that doctrine is meant to change what people do on the following Tuesday.

He puts the same thought another way in a sermon for the Ascension: what was visible in our Redeemer has passed over into the sacraments of the Church. The Incarnation continues to be reachable in the ordinary rites a parish celebrates every week.

What a Reader Can Take From Leo

Precision in words is a form of charity

Leo spent years on a dispute about a preposition. The alternative was a Church that could no longer say clearly who it was worshipping. Getting the words right about God is not pedantry, and vagueness usually protects an error rather than a person.

Show up when there is no army behind you

He went out to meet Attila with two civil servants and no force at all, and did it again three years later with the Vandals. Whatever the historians conclude about the causes, he went. Most of what is asked of ordinary Christians is that specific and that unarmed.

Your dignity is a fact to live up to

The Christmas sermon is addressed to people who already know they are Christians and are behaving as though they were not. Leo's argument is that the Incarnation has changed your standing, and conduct should follow the fact. Start with the thing you already know you should stop doing.

Frequently Asked Questions

Why is Pope Leo I called "the Great"?

Because of the combination of what he did: the Tome that settled the Church's language about Christ at the Council of Chalcedon in 451, his defence of Rome during the invasions of Attila in 452 and Genseric in 455, and his articulation of the authority of the see of Peter. He is one of three popes called "the Great," with Gregory I and Nicholas I.

What is the Tome of Leo?

The Tome is a letter Leo wrote in June 449 to Flavian, bishop of Constantinople, stating that Jesus Christ is one person in two natures, human and divine, each nature keeping its own properties. The Council of Chalcedon read and adopted it in 451, and the bishops are recorded as acclaiming "Peter has spoken through Leo."

Did Pope Leo really stop Attila the Hun?

Leo was part of an embassy, with two senior imperial officials, that met Attila in northern Italy in 452, and Attila withdrew afterwards. Historians also point to plague and famine in Italy and to attacks on Hunnic territory in the east as causes. The story of St. Peter and St. Paul appearing with drawn swords comes from later accounts and is legend attached to a real meeting.

When is the feast of Pope St. Leo the Great?

10 November in the Roman Calendar, the day of his death in 461. It was kept on 11 April before the calendar was revised in 1969. Byzantine churches commemorate him on 18 February.

What did the Council of Chalcedon decide?

That Jesus Christ is one and the same Son, acknowledged in two natures, without confusion, without change, without division and without separation, the property of each nature preserved and concurring in one person. It rejected both the teaching that Christ's humanity was absorbed into his divinity and any account that split him into two persons.

Which churches rejected the Council of Chalcedon?

The churches now known as Oriental Orthodox: the Coptic, Syriac, Armenian, Ethiopian, Eritrean and Malankara churches. They object to the phrase "in two natures" and confess one incarnate nature of the Word, understood as full divinity and full humanity united without confusion. Joint declarations signed since the 1970s state that both sides hold the same faith in Christ, and the communions remain separate.