Leo, bishop, to Empress Pulcheria Augusta.

Chapter I: Leo Urges Pulcheria’s Zeal Against Eutyches

We have often proven by many examples how great a protection the Lord has prepared for His Church through Your Clemency. Whatever priestly zeal has achieved against those who have assailed Catholic truth in our times redounds chiefly to your glory — for, taught by the Holy Spirit, you submit your authority wholly to Him by whose gift and protection your reign is granted.

Through the report of our brother and fellow bishop Flavian, we have learned of the dissension in the Constantinopolitan Church that was stirred up by Eutyches, as the text of the synodal acts makes clear. It befits your glory to suppress this error — which I believe flows more from ignorance than from cunning — before it gathers strength from the obstinate agreement of the imprudent. For ignorance often leads to grave lapses, and careless simplicity frequently falls into the devil’s snare.

Through this, I understand, the spirit of falsehood crept into Eutyches — who, thinking to honor the majesty of the Son of God piously by denying the truth of our nature in Him, supposed that the entire reality of the Word made flesh was of one and the same substance. As much as Nestorius fell from the truth by asserting Christ was born from the Mother only as a man, so too this man deviates from the Catholic path — he who does not believe that our substance was born from the same Virgin, wishing what was born there to be understood as purely divine, so that what bore the servant’s form and was like and conformable to us was a mere image of our nature, not the truth of it.

Chapter II: Christ Must Be a Man of Our Race; The Mystery of the Incarnation Fulfills What the Patriarchal Appearances Only Foretold

It avails nothing to call our Lord, the Son of the Blessed Virgin Mary, a true and perfect man if He is not believed to be a man of her race, as the Gospel proclaims. Matthew says: The book of the genealogy of Jesus Christ, Son of David, Son of Abraham (Matt. 1:1) — and in this way traces the order of human descent, bringing the line of generations down to Joseph, to whom the Lord’s Mother was betrothed. Luke, retracing the succession of generations backward, reaches the very first of the human race (Luke 3:23), to show that the first Adam and the last Adam are of the same nature.

The omnipotence of the Son of God could indeed have appeared to teach and justify men in the manner in which He appeared to the patriarchs and prophets in bodily form — entering into a wrestling match (Gen. 32:24), holding conversation, not refusing the offices of hospitality, or even accepting food set before him (Gen. 18). But those were signs pointing to this man — announcing that His truth was to be drawn from the lineage of the foregoing fathers, as the mystical signs foretold.

No mere figures, therefore, could fulfill the mystery of our reconciliation1 — arranged before eternal ages — for the Holy Spirit had not yet come upon the Virgin, nor had the power of the Most High overshadowed her, so that within her inviolate womb, with Wisdom building itself a house (Prov. 9:1), the Word might become flesh (John 1:14), and the form of God and the form of a servant might be united in one fitting person, and the Creator of the ages be born in time, and He through whom all things were made be Himself born among all things.

For unless the new man, made in the likeness of sinful flesh, had taken our old condition upon himself — and being consubstantial with the Father had deigned also to be consubstantial with the mother, and being free from sin alone had united our nature to himself — the whole human race would remain under the devil’s yoke; nor could we make use of the Conqueror’s victory if it had been won outside our nature.

Chapter III: The Mystery of Regeneration Flows from the Incarnation; The Apostolic See Maintains Both Severity Toward the Obstinate and Mercy for the Corrected

From this marvelous participation the mystery of our regeneration shone forth — so that through the same Spirit by whom Christ was both conceived and born, we also, who are born of fleshly desire, might be born again from a spiritual origin. This is why the Evangelist says of believers: Who were born not of blood, nor of the will of the flesh, nor of the will of man, but of God (John 1:13). Whoever excludes from his faith the very thing that principally saves us can have no share in that ineffable grace, nor can he be counted among the adopted sons of God.

I grieve deeply and am profoundly distressed that one who was formerly praiseworthy for his purpose of humility now dares to press such vain and foolish claims against the singular hope of us and our fathers. Seeing that Catholic ears were displeased with his folly, he should have withdrawn from his opinion; he should not have moved the Church’s bishops to the point of deserving to receive a sentence of condemnation — which, if he persists in his error, the will of the See could not relax. The moderation of the Apostolic See, however, maintains both: that it employs severity toward the obstinate and does not deny mercy to those who are corrected.2

Chapter IV: Leo Sends Legates in His Stead; The Apostolic Creed as Weapon Against Heresy

The most august and Christian emperor has convened a council to be held at Ephesus, setting an extremely short and narrow time for the assembly — the first day of August as the appointed day for the gathering — yet from the third day before the Ides of May, when we received his written decree, most of the priests who would be sufficient for the task would need to spend that time in preparation. Nor is it to be expected that I myself attend the council in person, even if custom had required it: the uncertainty of present circumstances does not allow me to withdraw from the people of this city. The very uncertain situation would not permit me to be absent from the people of so great a city — and they would be cast into a certain desperation of spirit if, for the occasion of an ecclesiastical cause, I were seen to wish to abandon my homeland and the Apostolic See.

Since you therefore know this to be in the public interest — with your clemency granting its pardon — I have not denied [my presence] to the citizens’ charity and prayers. Consider me also present in these brothers of mine whom I have sent in my stead3 — and to them I have clearly and fully shown, from the series of events and from the profession of the man in question, what must be upheld according to the cause. For it is not some small or obscure portion of our faith that is in question; this foolish presumption assaults what the Lord has willed that no one of either sex in His Church should be ignorant of.

For the brief and perfect confession of the Catholic Creed, sealed by the sentences of the twelve apostles, is so fortified by heavenly defense that all heretical opinions can be cut down by its sword alone. If Eutyches had received the fullness of this Creed with a pure and simple heart, he would deviate in nothing from the decrees of the most sacred Nicene Council; and he would understand that the holy Fathers established this: that against the apostolic faith — which is one and only one — no ingenuity may exalt itself and no eloquence may rise. Therefore strive by the custom of your piety to drive from all minds this blasphemous folly against the singular mystery of human salvation. And if he who has fallen into this temptation comes to his senses and condemns his own error by a formal written satisfaction, let communion not be denied him with his own order — which matter we have also written to our holy Bishop Flavian, that if the wickedness is abolished, the error may be removed.

Given on the Ides of June, in the consulship of Asturius and Protogenes, most illustrious men.4