Presence in Absentia: Pope Leo I and the Council of Chalcedon

Presence in Absentia
Pope Leo I and the Council of Chalcedon

“St. Leo is universally proclaimed as ‘Doctor of the Church's unity.’" (1)
– Pope John XXIII

“There were aspects of Chalcedon that [the Armenian Church objected to]; particularly in Pope Leo’s Letter to Flavian.” (2)
– Karekin I, Catholicos of the Armenian Apostolic Church

Though Pope Leo I did not attend the Council of Chalcedon in 451 CE, his influence is indisputably evident in the Council proceedings and decisions, as well as its aftermath. However, it is the nature of Leo’s influence that is debated to this day: while the Roman Catholic Church stresses Pope Leo’s role in formulating the Chalcedonian Definition of Faith, and views his objections to Canon 28 as a defense of apostolic heritage, other churches such as those in Armenia and Egypt perceive Leo’s Christology as dangerously Nestorian, his politics as self-serving. Whether Pope Leo is perceived as bringing unity or division to the Christian Church is largely determined by how one interprets the Christology espoused in his famous Letter to Flavian. Scrutiny of this document and the political maneuverings surrounding it reveal why some regard Leo as the peace-bringing successor to Peter, while others view him as the principal impetus for the post-Chalcedonian schism.

To a significant degree, it could be said that the crux of the disagreements that plagued the 5th-century Church was simply a semantic misunderstanding, an impassioned struggle to formulate the vocabulary which would accurately express theological thought; certainly, the use of precise language was considered critical to the parties involved. The Antiochene school of Syrian theologians utilized terms such as two persons, conjoined and person of union, stressing “the distinction between the two constituent elements in Christ, Godhead and manhood.”(3) Meanwhile, "The Alexandrian school... gave prime emphasis to the unity of Christ... expressed with such formulae as one incarnate nature, one hypostasis, [and] two natures in contemplation alone."(4) The difference between the two schools of thought is rooted in their soteriology, and often expressed in terms of direction: the Alexandrian “Christology from above,” where God elevates mankind from sin through Christ’s divinity, versus the Antiochene “Christology from below,” where mankind transcends sin through Christ’s humanity. Such differences in perspective fueled Christological controversy throughout this period of Christian history, spurring countless misconceptions of Christ’s nature which the Church fought off, such as Nestorianism. The latest heretical threat had come from Eutyches, who was perceived as overreacting to Nestorianism by asserting that Christ’s humanity was subsumed by his divinity. For Eutyches, “the flesh of Christ was not in his view consubstantial with ordinary human flesh”(5) – a notion that Leo, like many others, saw as undermining the doctrine of salvation.

“Through the most blessed Peter, chief of the Apostles, the Holy Roman Church holds the principate over all the churches in the world” wrote Pope Leo, as quoted by Leo Donald Davis.(6) It is with this self-image as the definitive leader of Christianity that Leo responded to the Eutychian threat in a letter addressed to Flavian, bishop of Constantinople. Composed circa 449, the letter was suppressed at the Council of Ephesus that same year, but was promoted forcefully at the Council of Chalcedon in 451. This Tome, first drafted by Leo’s secretary, Prosper of Aquitaine, was a “committee document, almost a Cento, a cut and paste editorial work that assembles all the traditional aspects of prior Latin theology, with an especial emphasis on Augustine.”(7) C.R. Norcock also points out that numerous sections of the Tome appear to have been taken from an early 5th-century letter by St. Gaudentius of Brescia to “Paul the deacon.”(8)

By “drawing upon” the works of renowned Latin theologians, Leo’s letter was assembled in response to the specific crisis identified with the teachings of Eutyches, but was viewed by the Pope as the quintessential statement of theological truth, and promoted by him as a resolution to the general Christological arguments that had been raging for generations between the Antiochene and Alexandrian schools of thought. By presenting his “two natures/one person” conception of Christ, it seemed “the Antiochenes could find … insistence on the reality and independence of the two natures; the Alexandrians, Cyril’s basic insight that the person of the Incarnate is identical with that of the Divine Word."(9)

But Leo’s Christology was not straightforwardly identical to that of Antioch or Alexandria. His uniquely Latin understanding of salvation (which he had inherited from his predecessors, including Tertullian, Hilary of Poitiers, St. Ambrose of Milan, and St. Augustine) casts Christ in the role of mediator, who “as man’s representative … might pay the debt [of sin] and remove man’s guilt through an expiatory sacrifice.”(10) The Tome of Leo is replete with this understanding of Atonement, as in the following passages:

“[The Incarnation’s] whole purpose is to restore humanity … Overcoming the originator of sin and death would be beyond us, had not he whom sin could not defile, nor could death hold down, taken up our nature and made it his own.”(11)

“[The] mediator between God and humanity, the man Christ Jesus could both on the one hand die and on the other be incapable of death.” … “His subjection to human weaknesses in common with us did not mean that he shared our sins. He took on the form of a servant …”(12)

Leo’s Latin soteriology focuses “attention, not so much (like the Alexandrians) on the meaning of the Incarnation, or (like the Antiochenes) on that of the Resurrection, as on that of Calvary, as they lay stress on the forgiveness which it brings.”(13)

The conception of Christ’s role as mediator serves as the centerpiece for Leo’s “two natures/one person” Christology, where the Logos is united with a human body. It is also the point of departure for disputes regarding the degree of unity that Leo’s concept achieved. Pope Leo endeavored to depict a true union, describing it as “co-eternal and consubstantial with the Father,”(14) and stressed that, “though the Incarnation involved a self-emptying, this should be understood as a stooping down whereby the Word underwent no diminution of His omnipotence."(15) But Leo also strove to delineate Christ’s two natures, stating that “The Word performs what belongs to the Word, and the flesh accomplishes what belongs to the flesh. One of these performs brilliant miracles, the other sustains acts of violence.”(16) Such statements of Christ’s dual natures suggested less of a union than a juxtaposition of the divine and human – an idea which alarmed a good number of bishops, who sensed a decidedly Nestorian undertone at work in Leo’s model. Though Leo’s Tome offered strong statements to counter such alarm, it also constantly returned to the idea of separation, asserting that it was Jesus’ human nature that wept over the death of a friend, while insisting it was Christ’s divine nature that walked on water. By posing such seemingly contradictory views, and repetitively emphasizing the separation of the two natures, it is no wonder that the Tome of Leo was met with resistance at Chalcedon, and was seen as fomenting discord in the centuries to follow.

Leo’s writings were also problematic because of language. As a western theologian, relying almost exclusively on Latin, the Pope had difficulty communicating with the rest of the Christian world, which was largely Greek speaking. Leo could easily mistranslate Greek writings, just as Greek readers could often misinterpret the Pope’s Latin. Comparisons of early drafts of Leo’s Tome with the later, finished version show revisions which indicate he was aware of this issue, and tried to avoid problems by choosing his words carefully. For example, in one important section: “So it is on account of this oneness of the person, which must be understood in both natures …”(17) the word Naturae “was substituted for substantiae in the original version, clearly to avoid problems in Greek translation.”(18)

Unfortunately, Leo was “handicapped through not being able to appreciate that the Greeks could use nature in the sense of persona,”(19) and any confusion between these two terms was dangerous. Leo’s use of the word forma could also cause the same misunderstanding. When Leo wrote that “the activity of each form is what is proper to it in communion with the other,”(20) the phrase “each form” (forma) could be understood as attributing Christ’s actions to two different persons or hypostases, an idea which directly contradicted earlier theological literature, such as the Formula of Reunion, and the Fourth Anathema of Cyril’s Third Letter to Nestorius.(21)

Even when Leo did use the term persona correctly, he did so in a controversial context. In declaring that “for although there is in the Lord Jesus Christ a single person who is of God and of man,” the Pope came close to rightly emphasizing the singularity of Christ’s humanity and divinity. But he shifts the focus back to a duality, by beginning the statement with the conjunction although, and completing the sentence with the words “the insults shared by both have their source in one thing, and the glory that is shared in another.”(22) Riddled with potential language landmines such as these, the Tome was destined to be met with suspicion at Chalcedon.

Pope Leo, following a long-established precedent, refused to attend the Council of Chalcedon, sending in his place a number of legates who “attempted to create an impression of being in charge. Their role, they insisted, was not to deliberate along with the assembled bishops but rather to inform them of the pope’s judgments.”(23) As far as everyone from the Roman camp was concerned – including the dictatorial Emperor Marcian – there was little to do at the council other than to officially endorse Leo’s Tome. Though the Pope regarded himself as the supreme leader of the ecumenical Church, it is likely that most bishops at Chalcedon “understood their relationship to Rome in less subordinate terms."(24)

The shortcomings of the Tome became immediately apparent the moment the document was read at the Council of Chalcedon’s second session, with Illyrian and Palestinian bishops loudly objecting to those sentences which stressed a separation of natures: The Word performs what belongs to the Word, and the flesh accomplishes what belongs to the flesh. One of these performs brilliant miracles, the other sustains acts of violence. “This led, presumably, to detailed discussion that was reduced in the record to a series of citations from Cyril of Alexandria, intended to demonstrate agreement between Leo and Cyril.”(25)

If there is anyone whose presence in absentia was felt more keenly at the Council of Chalcedon than Pope Leo’s, it was that of Cyril of Alexandria, who had died some seven years prior. In numerous letters composed from his see in Egypt, Cyril had long-ago mapped out a Christology of “one incarnate nature of the divine Logos,”(26) providing new terminology to define the unification of the Logos with flesh as a hypostatic and natural union. It was Cyril’s views that were almost universally accepted within the Church, and whose writings provided “the yardstick of orthodoxy”(27) for everyone at Chalcedon. Only by comparing the inflammatory statements in Leo’s letter to similar ones made by the venerated Cyril of Alexandria was the council able to accept Leo’s Letter to Flavian as orthodox. And when, at the fourth session of the council, each bishop was called upon to affirm Leo’s Tome, “Of the one hundred and sixty one bishops who registered their official ‘acclamations’ in the Acts of the council, almost every one of them included a specific judgment that Leo had been faithful to Cyril.”(28)

The council almost certainly would not have incorporated Leo’s Christology into their Definition of Faith were it not for the deceased Cyril, and the living Roman Emperor Marcian. When it was finally resolved to produce a Definition of Faith (after protracted arguments that it was unnecessary), a first draft was rejected by Leo’s legates at the council for not adequately incorporating the Pope’s “two natures” philosophy. At the fifth session, when resistance to a new definition continued, the Emperor Marcian threatened to move the council to the West (insinuating that Leo would personally take over the matter), and elected a council subcommittee to act. Marcian and the Roman legates - and Leo, from afar – insisted upon “a formal affirmation of a continuing duality in Christ after the union."(29) It became clear that the council could not adjourn without producing a new Definition of Faith that in some way embraced Leo’s Tome.

The final product was a statement that appeared in agreement with Leo’s Tome while utilizing as little of it as possible. After first introducing the synodical letters of Cyril, an entire paragraph is dedicated to the introduction of Leo’s letter, making much of Leo himself, and his role as the “primate of greatest and older Rome.”(30) When the definition finally gets round to its profession of faith, a kind of tight-rope walk can be detected in its wording as the bishops labored under the Roman order to provide a clear statement about two natures existing after the incarnation, while simultaneously attempting to satisfy those who took a more Alexandrian, miaphysite stance.

Once again, the council members looked to Cyril as the ultimate authority, couching the thorny terms of Leo’s Christology in familiar and comfortable Cyrillian expressions. Every reference to “two natures” is made with an emphasis on unity, as in the following excerpt:

“The property of both natures is preserved and comes together into a single person and a single subsistent being; he is not parted or divided into two persons, but is one and the same only-begotten Son, God, Word, Lord Jesus Christ, just as the prophets taught from the beginning.”(31)

Numerous sections of the definition quote virtually verbatim from Cyril’s letters.(32) The definitional clause “the difference of the natures being in no way destroyed by the Union” was taken word for word from Cyril’s Second Letter to Nestorius. And at least three major statements in the Chalcedonian Definition of Faith (CHALCEDON) appear to have been lifted directly from Cyril’s Letter to John on Antioch (CYRIL):

1. CHALCEDON: “We all with one voice teach the confession of one and the same Son, our Lord Jesus Christ … truly God and truly man, of a rational soul and a body.”

CYRIL: “We confess that Our Lord Jesus Christ, the Only Begotten Son of God is perfect God and perfect Man, of a rational soul and body.”

2. CHALCEDON: “In these last days for us and for our salvation was born of the virgin Mary according to the manhood.”

CYRIL: “In the last days the same for us and for our salvation from Mary, the virgin God-bearer, as regards his humanity.”

3. CHALCEDON: “The same one is consubstantial with the Father according to the Godhead, and consubstantial with us according to the manhood.”

CYRIL: “Consubstantial with the Father as regards his divinity, and the same consubstantial with us as regards his humanity.”

Even sections of the definition often attributed to Pope Leo can be argued to have come from Cyril, such as the definition’s oft-cited “four adverbs”:

CHALCEDON: [the two natures undergo] “no confusion, no change, no division, no separation.”

A case might be made for Leo as the author of these striking terms. In his Tome, the Pope discusses Christ’s earthly manifestation and its relationship with God as being “not later in time, not lower in power, not unlike in glory, not distinct in being.” That Leo employs four lyrical qualifying terms regarding the union can be seen as the inspiration for the more succinct four adverbs used in the Definition of Faith. But a clearer link can be identified between the definition and a statement made by Cyril in his First Letter to Succensus, where he writes that [the Word and the flesh are united] “without confusion, without change, and without alteration.” These three terms seem obviously akin to the four used in the definition. Especially considering the council members’ attitude toward Cyril as the “yardstick of orthodoxy,” it is unlikely they would have been inclined to use Leo’s writing as their inspiration when Cyril had anything to say on the subject.

With so much of Cyril’s imprint on the Chalcedonian Definition of Faith, one has to wonder exactly how and where Leo’s Tome was utilized. McGuckin writes that “The main Leonine contribution to the Chalcedonian settlement is the phrase: ‘the property of each nature being preserved and concurring in one prosopon.”(33) Leo’s Tome states it as “The proper character of both natures was maintained and came together in a single person.” Yet even this bit seems included as a Leonine confirmation of Cyril and the Alexandrian Christology which stressed that “in this one Person are clearly evident the two elements of Godhead and manhood.”(34)

Leo’s supporters at Chalcedon, including the legates who were technically presiding over the council, as well as the formidable emperor, sensing that the emerging definition was short on Leonine representation, pushed for one small change in wording. The phrase “in two natures” (as opposed to “of two natures”) was considered a definitive assertion of Latin Christology, as it maintained a distinction of natures after the Incarnation. By making this revision, the subcommittee was able to satisfy the Latin contingent, and offer a finished Definition of Faith to the council. Though this may have been perceived as some small victory on the part of Rome (and a clear refutation of Eutyches), in truth it was another restatement of Cyrillian belief. Cyril had never objected to the appreciation of two natures in Christ after the Incarnation, as long as the union was never compromised. This, in the end, epitomized the difference between Leo and Cyril: Leo observed two sides to a coin, while Cyril perceived the coin as a whole.

This difference in perception incited the divergent reactions to Leo’s Tome and the Chalcedonian Definition of Faith. To those with Alexandrian leanings, Chalcedon had added to the faith of Nicaea, and innovation to this most revered first council was considered blasphemous. What’s more, the Definition of Faith had not clearly proclaimed the hypostatic union, nor had it plainly declared who suffered on the cross, or “that the person of the union was the pre-existent person of the Word.”(35) Acclamation of Leo’s Tome was perhaps the worst offense, convincing many of the Council of Chalcedon’s Nestorian inclinations, with repetitive insistence that “Jesus Christ was capable of death in the one nature and incapable of death in the other.”(36) To the dissenters, Leo’s emphasis on the two natures “so separates, and personalizes, what is divine and what is human in Christ that the hypostatic union is dissolved.”(37) What would conclusively be dissolved after Chalcedon was the ecumenical Church, as controversy over the council and its statement of faith crystallized two outlooks which for many were irreconcilably opposed: dyophysitism (maintaining Christ’s two natures) and miaphysitism (emphasizing unity).

For Leo, Chalcedon was a failure, and initially he rejected it entirely. With his self-image as Christ’s chosen leader of the Church, the Pope had expected nothing from this council other than the official acclamation of his Tome. The fact that so little of his work actually made its way into the Definition of Faith could not have escaped his notice, and would likely have wounded his sense of pride, and perhaps even alarmed him that the Church was falling into heresy (by rejecting his dictates). But the Pope expressed his objections to Chalcedon almost exclusively on the adoption of canon 28, which confirmed an elevated status to the see of Constantinople, reading (in part):

“The fathers rightly accorded prerogatives to the see of older Rome, since that is an imperial city; and moved by the same purpose the 150 most devout bishops apportioned equally prerogatives to the most holy see of new Rome, reasonably judging that the city which is honoured by the imperial power and senate and enjoying privileges equaling older imperial Rome, should also be elevated to her level in ecclesiastical affairs and take second place after her.”(38)

Though it’s highly unlikely that recognition of the see of Constantinople was intended by the Council of Chalcedon (or the Council of Constantinople, which established the precedence in 381) as an affront to Rome, it is difficult to imagine that Leo could have seen it as anything less than threatening. The wording of the canon implies that top ecclesiastical primacy was conceded to the Church of Rome not because of apostolic succession, or Rome’s association with the martyrs Peter and Paul, but because of Rome’s original role as the center of government. Having witnessed the fall of Rome as the imperial power, the Roman papacy was now witnessing the meteoric rise of Constantinople as an ecclesiastic power. Leo could not help but fear that, “while in earlier centuries eastern churchmen had often appealed to the Roman see, such appeals would in future be directed to the emperor or archbishop at Constantinople, with the result that the status of Rome would be effectively reduced to that of the patriarchal see of the western provinces. In this sense rivalry for influence between Rome and Constantinople was the root cause of the debate over Canon 28.”(39)

Discreetly, Leo officially objected to canon 28 as an innovation of canon 6 of Nicaea, which had formally recognized the major sees of Rome, Alexandria, and Antioch (at a time when Constantinople was just coming into existence). He also claimed sensitivity to the usurpation of Alexandria and Antioch’s authority. Both protests could be interpreted as evidence of the Pope’s sense of peril: if canon 6 of Nicaea could be modified, and the once sacrosanct status of Alexandria and Antioch be overthrown, how long before Rome would lose its place of honor to the Eastern upstart? Ultimately, not wanting to appear as a supporter of heretical views, Leo approved the Council of Chalcedon, though he never accepted canon 28.

To this day, Pope Leo I’s reputation in Christian history is disputed, the role of his Tome as a unifier or divider of the Church still contested. But in terms of the 5th-century semantic struggle to articulate theological thought, Leo and his Letter to Flavian certainly played an important role. His particular use or avoidance of terms such as nature, person, and hypostasis helped theologians engage in debate, forcing them to standardize their terminology, and better communicate what they did and did not believe. Such communication is apparently ongoing, as representatives of all sides continue to discuss what theologians like Leo and his peers at Chalcedon truly intended.


1. Speech delivered on Nov. 11, 1961, archived online by the Vatican Holy See.
2. Guaita 102.
3. Acts of the Council of Chalcedon Vol. I, Introduction, 61.
4. Ibid.
5. Davis 171.
6. Ibid. 193.
7. McGuckin, “The Long Road to Chalcedon,” 14.
8. Norcock 595.
9. Davis 176.
10. Sellers 184.
11. Decrees of the Ecumenical Councils Vol. I 77.
12. Ibid. 78.
13. Sellers 184.
14. Decrees of the Ecumenical Councils Vol. I 80.
15. Davis 175.
16. Decrees of the Ecumenical Councils Vol. I 79.
17. Ibid. 80.
18. Green 213.
19. Sellers 233.
20. Decrees of the Ecumenical Councils Vol. I 79.
21. “If anyone interprets the sayings in the Gospels and apostolic writings, or the things said about Christ by the saints, or the things he says about himself, as referring to two prosopa or hypostases, attributing some of them to a man conceived of as separate from the Word of God, and attributing others (as divine) exclusively to the Word of God the Father, let him be anathema.” McGuckin 274.
22. Decrees of the Ecumenical Councils Vol. I 80.
23. Acts of the Council of Chalcedon Vol. I, Introduction, 11.
24. Ibid. 21.
25. Acts of the Council of Chalcedon Vol. II, 4.
26. Sellers 141.
27. Acts of the Council of Chalcedon Vol. I, Introduction, 66.
28. McGuckin 235.
29. Acts of the Council of Chalcedon Vol. I, Introduction 69.
30. Decrees of the Ecumenical Councils Vol. I 85.
31. Ibid. 86.
32. In the following section, all statements from the Chalcedonian Definition of Faith and the “Tome of Leo” are quoted from Decrees of the Ecumenical Councils Vol. I; all statements taken from the letters of Cyril are quoted from McGuckin.
33. 238.
34. Sellers 143.
35. Davis 197.
36. Ibid. 196.
37. Sellers 266.
38. Decrees of the Ecumenical Councils Vol I. 100.
39. Acts of the Council of Chalcedon Vol. III 72.


The Acts of the Council of Chalcedon: Vols. I-III. Trans. Richard Price and Michael Gaddis. Liverpool: Liverpool UP, 2005.

Davis, Leo Donald. The First Seven Ecumenical Councils (325-787): Their History and Theology. Collegeville, MN: The Liturgical Press, 1983.

Decrees of the Ecumenical Councils. Ed. Norman P. Tanner S.J. London: Sheed & Ward, and Washington, D.C.: Georgetown UP, 1990.

Green, Bernard. The Soteriology of Leo the Great. London: Oxford UP, 2008.

Guaita, Giovanni. Between Heaven and Earth: A Conversation with His Holiness Karekin I. New York: St. Vartan Press, 2000.

McGuckin, John. Saint Cyril of Alexandria and the Christological Controversy. Crestwood, NY: St. Vladimir’s Seminary Press, 2004.

Norcok, C.R. St. Gaudentius of Brescia and the Tome of St. Leo. JTS 15. 1913-1914, pp. 593-596.


Sellers, R. V. The Council of Chalcedon: A Historical and Doctrinal Survey. London: S.P.C.K., 1953.

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