Leo, bishop, to Leo, Augustus.
Chapter I: Leo Rejoices in the Emperor’s Faith and Urges That the Chalcedonian Definition, Confirmed from the Rock on Which the City of God Is Built, Never Be Reopened
My heart rejoices greatly in the Lord, and I have ample reason for gratitude, knowing that the most excellent faith of your clemency is in every way increased by the gifts of heavenly grace, and finding in you a priestly devotion of soul growing through increasing diligence. For in the words of your piety it is clear beyond doubt what the Holy Spirit is working through you for the salvation of the whole Church, and how greatly all the faithful must desire that your empire be extended to the glory of all — you who, above and beyond the management of temporal affairs, devote yourself with unwavering commitment to the service of divine and eternal design through religious providence: so that the Catholic faith, which alone gives life and alone sanctifies the human race, may remain in one confession, and the disagreements that spring from the diversity of earthly opinions may be driven away from the solidity of that rock upon which the city of God is built, most glorious emperor. These gifts of God will at last be granted to us only if we are not found ungrateful for what has been provided, and do not pursue the opposite of what we have received as though it were nothing. For to seek what has been revealed, to re-examine what is perfect, and to overturn what has been defined — what is this other than failing to give thanks, and stretching wicked appetite toward the fruit of the forbidden tree? Since therefore you are pleased to watch over the peace of the universal Church and the guardianship of the Catholic faith with careful solicitude, you clearly see what great snares the heretics are laying — that among the disciples of Eutyches and Dioscorus, and the one whom the Apostolic See shall appoint, some more painstaking inquiry, as though nothing had previously been defined, may be conducted. And what all the Catholic priests of the world approve and rejoice to be firmly settled in the holy Council of Chalcedon is to be made to appear uncertain — to the injury even of the most sacred Council of Nicaea. For what was settled in our times at Chalcedon concerning the Incarnation of our Lord Jesus Christ is what that mystical number of Fathers already defined at Nicaea: that the Catholic confession must neither believe the Only-begotten Son of God inferior to the Father in any way, nor suppose that when He became the Son of Man He lacked the true substance of our flesh and soul.
Chapter II: Leo Declares That the Defined Faith Cannot Be Reopened and That No Communion Is Possible with Those Who Contradict the Divine Mysteries
It must therefore be treated as detestable and constantly avoided that heretical fraud attempts to obtain this — that things piously and fully defined be recalled for re-examination, so that we seem to be pressed by the judgment of the condemned themselves to reconsider what is clearly consistent with all prophetic, evangelical, and apostolic authority. Those who dissent from what has been established from on high must be left to their own opinions, and must themselves depart, with their chosen perversity, from the unity of the Church. For it is in no way possible that those who dare to contradict the divine mysteries should be joined to us in any form of communion. Let them boast in the vanity of their eloquence and glory in the cleverness of their arguments, which is hostile to faith — but we are pleased to obey the Apostle’s command: See that no one deceives you through philosophy and the empty seduction of men (Col. 2:8). For if I rebuild what I have pulled down, I make myself a transgressor (Gal. 2:18), and I submit myself to the penalties established not only by the authority of blessed Emperor Marcian but by my own consent as well. For as you have said with holy truth: perfection admits of no addition, and fullness of no supplement. Knowing you, venerable emperor, to be deeply formed in the truth and unshaken in any part of the faith, and capable by your holy and perfect judgment of distinguishing right from wrong — I beg you not to attribute my caution to lack of confidence, for this caution serves not only the universal Church but also your own glory: that neither the wickedness of heretics may be seen to have grown under your reign, nor the security of Catholics to have been disturbed.
Chapter III: Leo Announces He Is Sending Legates from the Apostolic See Not to Dispute, but to Instruct and to Demonstrate Who Is and Who Is Not Catholic
Although I am fully confident in the strength of your piety in every respect, and see clearly that no error can deceive your faith, I am nevertheless complying with your command by sending some of my brothers — who will stand before you in my stead and, though the rule of Apostolic faith is of course already well known to you, will demonstrate and make known to all and prove that those who do not follow the definitions of the venerable Council of Nicaea or the rules of the holy Council of Chalcedon are not to be counted among Catholics at all — for the sacred decrees of both councils clearly spring from the same evangelical and apostolic source, and whatever is not from the nourishment of Christ is poison. Know well, venerable emperor, that those I undertake to send are going not to do battle with the enemies of the faith, nor to debate with anyone — they come from the Apostolic See — for concerning the things defined as God pleased at both Nicaea and Chalcedon, we dare enter into no negotiation, as though what the Holy Spirit has established with such authority were doubtful or weak.
Chapter IV: Leo Refuses to Admit Heretics to Debate, Calls for the Liberation of Alexandria, and Warns of Divine Punishment
For the instruction of those younger in faith who, after the food of milk, hunger for more solid nourishment, the assistance of our ministry must not be denied. And just as we do not despise the simpler, so we hold back from the rebellious heretics — mindful of the Lord’s precept: Do not give what is holy to dogs, nor cast your pearls before swine (Matt. 7:6). It is altogether unbecoming and unjust to admit to free debate those whom the Holy Spirit designates through the prophet saying: Foreign children have dealt falsely with me (Ps. 17:46). And even if they were not actively resisting the Gospel, of them it is written: They profess to know God, but in their deeds they deny it (Tit. 1:16). We wish to reserve vengeance for the impious plunderer and cruel parricide to the judgment of the Lord, that it may fall back upon him and not prevail against us. Nor should you suffer the lamentable captivity of the holy Alexandrian Church to be prolonged any further — for it is owed the restoration of its liberty through the support of your faith and justice, so that throughout all the cities of Egypt the dignity of the Fathers and the sacerdotal right may be restored.
Given on the twelfth day before the Kalends of April, in the consulship of Leo and Majorian, most august Emperors.
Footnotes
- ↩ This letter was transmitted to the Emperor through Philoxenus, an imperial agent (agens in rebus) — a member of the imperial courier and intelligence service. The use of an imperial agent rather than Leo’s own personal representatives (Gerontius, Olympius, Julian, Aetius) indicates that the Emperor had specifically requested this reply. The dynamic is therefore slightly different from the proactive dispatches of the September and December 1 clusters: here Leo is responding to an imperial initiative on the Emperor’s own terms, while setting those terms firmly from the outset.
- ↩ The phrase soliditate illius petræ, supra quam civitas Dei ædificatur — “the solidity of that rock upon which the city of God is built” — fuses two great theological traditions. Petra invokes Matthew 16:18, the Petrine foundation on which the Church is built. Civitas Dei deliberately echoes Augustine’s great work, written 413–426, in which the city of God — the community of those ordered to God — is contrasted with the earthly city ordered to self. Leo’s fusion of the two is precise: the Petrine rock is not merely the foundation of the institutional Church but of the civitas Dei as the political-theological entity that transcends the kingdoms of the earth. The disagreements of earthly opinion belong to the civitas terrena; the Petrine rock is what the civitas Dei rests on, and the Roman bishop is its custodian.
- ↩ The image is Genesis 3 — the original sin of Adam and Eve reaching for the fruit of the tree God had forbidden. Leo’s deployment of it here is theologically precise: the desire to reopen what has been defined is not merely imprudent or premature; it follows the exact pattern of original sin. God has given the definition; to seek to re-examine it is to distrust the gift, to imagine that something more or better remains to be grasped, to stretch the appetite toward what divine authority has placed beyond reach. The allusion identifies the demand for a new council not as a theological inquiry but as an act of disobedience against a divine establishment.
- ↩ The phrase et eum quem apostolica sedes direxerit — “and the one whom the Apostolic See shall direct/appoint” — is one of the most explicit jurisdictional claims in the letter. In the context of the Eutychians’ demand for a new council, Leo is specifying the legitimate party to any doctrinal discussion: the Apostolic See’s own designee. This is simultaneously a claim about the Alexandrian succession: the legitimate candidate for the see of Alexandria is the one the Apostolic See designates. Alexandria was the second-ranking see in the Christian world; the claim that Rome designates its bishop is a claim of ordinary and immediate jurisdiction over the most senior episcopal appointment in the East outside Constantinople.
- ↩ This is the most remarkable personal statement in the letter. Marcian’s legislation of 451–452 prescribed penalties for those who disturbed the Chalcedonian definitions — making them legally binding in the empire. Leo states that these penalties apply to him personally, because he has agreed to them by his own consent (mea consensione firmavi). The implication is precise: Leo has not merely confirmed Chalcedon’s definitions as the expression of apostolic faith; he has personally bound himself to the legal consequences of disturbing them. The Roman pontiff does not consider himself above the settlement he has confirmed — not because conciliar authority is above him, but because he has freely and personally ratified it as the content of the faith he holds in Peter’s succession. To reopen them would make him a transgressor of his own act. This passage, read alongside the Gal. 2:18 citation immediately preceding it, approaches the infallibility register in a precise way. The irreformability attaches not to Chalcedon’s definitions as conciliar acts (grounded in divine inspiration, as in the quæ vere de cœlestibus prodiere decretis formula) but to Leo’s own confirmatory act: it is his ratification that he cannot undo. This is the distinction between conciliar irreformability and the irreformability of the Roman pontiff’s own defining act — the latter being what Vatican I’s Pastor Aeternus would later define explicitly.
- ↩ The phrase a sede apostolica profecturos… nullum audemus inire tractatum — “they come from the Apostolic See… we dare enter into no negotiation” — is the most concentrated statement in all of Leo’s correspondence of what the Apostolic See’s confirmation means in practice. The legates are not sent to weigh competing arguments or to explore whether the definitions might be refined; they are sent to instruct and to identify who is and who is not Catholic. The finality of the Roman confirmation is absolute: what the Holy Spirit has established through the Apostolic See is not a position in a debate; it is the settled standard against which all positions are measured. To enter into negotiation would be to treat the standard as one option among others — which is precisely what Leo will not do.
Historical Commentary