One of the most important figures in the history of both the office of the papacy and Christology (the study of the Personhood and mission of Jesus Christ) is Pope St. Leo I, known to subsequent generations as Leo the Great, revered Doctor of the Church in both the Catholic and Orthodox branches of Christianity. This former deacon under Popes Celestine I and Sixtus III was instrumental in defining the See of Peter as intimately tied with the Bishop of Rome’s stewardship of the Catholic Church.
Leo emphasized to an almost mystical degree the relationship between the man holding the office of pope and the chief disciple who was the first to be called “fisher of men.” The Petrine rock upon which Christ built his church continued unabated through the nascent centuries of the spread of the Gospel in the office of Supreme Pontiff. Leo viewed the Christian association with the former center of the Roman Empire as providentially ordained. Just as Romulus and Remus had founded the ancient civic caput orbis (“the head of the world”), Peter and Paul had been drawn to and martyred in Rome so that Christianity could take its rightful place in the center of the known world. The truth of the Gospel now supplanted the Empire as both the heart of civilization and the voice through which God’s salvific actions in history could be proclaimed to the ends of the earth.
Leo cherished and protected his adopted city, saving it from complete annihilation under Attila the Hun in 452 and Gaiseric the Vandal in 455. In his more than two decades (440-61 AD) on the Chair of Peter, Leo was able to redefine the relationship between Byzantine Christianity and the citizens of Western Europe. It was during this period that the Bishop of Rome came to take on an exalted role as the centralizing and adjudicating power in the dispute between local church figures.
However, Leo’s most lasting contribution to the Christianity we profess today was in his explanation of Christ’s metaphysical existence. Nestorius had claimed in the argument against describing Mary with the term theotokos (“God-bearer”), that Jesus was merely the son of Mary, an ordinary human being later imbued with a divine nature. This position was condemned by the Council of Ephesus in 431, and the church taught that it was valid to invoke Mary as the “Mother of God.”
As often happens with heresies of this type, the pendulum swung too far in the other direction, and a Constantinoplitan presbyter named Eutyches wrote to Leo claiming that Jesus had a human nature and divine nature which were uniquely combined, making him in essence different than human beings. In such a view, Jesus was much more than Nestorius’s merely human son of Mary; in fact he wasn’t human in any manner that could be made intelligible at all. As Eamon Duffy points out, “When this man appealed to Leo, the pope was horrified. He composed a treatise on the Incarnation, refuting Eutyches and teaching that in Christ there are two natures, human and divine, unmixed and unconfused, yet permanently and really united in a single person, so that it is possible to attribute to the humanity of Jesus all the actions and attributes of his divinity, and vice versa” (Saints and Sinners, 45). This treatise came to be called the Tome of Leo, and its acceptance by the Council of Chalcedon in 451 influenced the Nicene Creed that we profess today, in which we recognize Christ’s full humanity and full divinity. The bishops gathered at Chalcedon greeted the reading of the Tome with enthusiasm, claiming “Peter has spoken through Leo.”
Pope St. Leo was perhaps the most important figure since Constantine in enabling the Catholic Church to fill the power vacuum left by the declining Roman Empire. In Leo’s vision of the papacy, which allowed him to see himself as “head of an imperium which was not of this world, the church had found an ideal which would carry it through the collapse of the classical world, and into the future.” (Saints and Sinners, 47).
Michael M. Canaris of Collingswood is a Ph.D. candidate in systematic theology at Fordham.