Leo the bishop to the clergy, dignitaries, and people, residing at Constantinople.
Though we are greatly grieved at the things reported to have been done recently in the council of priests at Ephesus, because, as is consistently rumoured, and also demonstrated by results, neither due moderation nor the strictness of the Faith was there observed, yet we rejoice in your devoted piety and in the acclamations of the holy people1 , instances of which have been brought to our notice, we have approved of the right feeling of you all; because there lives and abides in good sons due affection for their excellent Father, and because you suffer the fulness of catholic teaching to be in no part corrupted. For undoubtedly, as the Holy Spirit has unfolded to you, they are leagued with the Manichaeans' error, who deny that the only-begotten Son of God took our nature's true Manhood, and maintain that all His bodily actions were the actions of a false apparition. And lest you should in aught give your assent to this blasphemy, we have now sent you, beloved, by my son Epiphanius and Dionysius, notary of the Roman Church, letters of exhortation wherein we have of our own accord rendered you the assistance which you sought, that you may not doubt of our bestowing all a father's care on you, and labouring in every way, by the help of God's mercy, to destroy all the stumbling-blocks which ignorant and foolish men have raised. And let no one venture to parade his priestly dignity who can be convicted of holding such detestably blasphemous opinions. For if ignorance seems hardly tolerable in laymen, how much less excusable or pardonable is it in those who govern; especially when they dare even to defend their mendacious and perverse views, and persuade the unsteadfast to agree with them either by intimidation or by cajoling.
Let such men be rejected by the holy members of Christ's Body, and let not catholic liberty suffer the yoke of the unfaithful to be laid upon it. For they are to be reckoned outside the Divine grace, and outside the mystery of man's salvation, who, denying the nature of our flesh in Christ, gainsay the Gospel and oppose the Creed. Nor do they perceive that their blindness leads them into such an abyss that they have no sure footing in the reality either of the Lord's Passion or His Resurrection: because both are discredited in the Saviour, if our fleshly nature is not believed in Him. In what density of ignorance, in what utter sloth must they hitherto have lain, not to have learnt from hearing, nor understood from reading, that which in God's Church is so constantly in men's mouths, that even the tongues of infants do not keep silence upon the truth of Christ's Body and Blood at the rite of Holy Communion2 ? For in that mystic distribution of spiritual nourishment, that which is given and taken is of such a kind that receiving the virtue of the celestial food we pass into the flesh of Him, Who became our flesh3 . Hence to confirm you, beloved, in your laudably faithful resistance to the foes of Truth, I shall filly and opportunely use the language and sentiments of the Apostle, and say: "Therefore I also hearing of your faith, which is in the Lord Jesus, and love towards all saints, do not cease to give thanks for you, making mention of you in my prayers that the God of our Lord Jesus Christ, the Father l of glory, may give you the spirit of wisdom and revelation in the knowledge of Him, the eyes of your hearts being enlightened that you may know what is the hope of His calling, and what the riches of the glory of His inheritance among the saints, and what is the exceeding greatness of His power in us, who believed according to the working of His mighty power which he has wrought in Christ, raising Him from the dead, and setting Him at His right hand in heavenly places above every principality, and power, and strength, and dominion, and every name which is named not only in this age, but also in that which is to come: and hath put all things under His feet, and given Him to be the head over all the Church which is His body, and the fulness of Him Who filleth all in all4 ."
In this passage let the adversaries of the Truth say when or according to what nature did the Almighty Father exalt His Son above all things, or to what substance did He subject all things. For the Godhead of the Word is equal in all things, and consubstantial with the Father, and the power of the Begetter and the Begotten is one and the same always and eternally. Certainly, the Creator of all natures, since "through Him all things were made, and without Him was nothing made5 ," is above all things which He created, nor were the things which He made ever not subject to their Creator, Whose eternal property it is, to be from none other than the Father, and in no way different to the Father. If greater power, grander dignity, more exalted loftiness was granted Him, then was He that was so increased less than He that promoted Him, and possessed not the full riches of His nature from Whose fulness He received. But one who thinks thus is hurried off into the society of Arius, whose heresy is much assisted by this blasphemy which denies the existence of human nature in the Word of God, so that, in rejecting the combination of humility with majesty in God, it either asserts a false phantom-body in Christ, or says that all His bodily actions and passions belonged to the Godhead rather than to the flesh. But everything he ventures to uphold is absolutely foolish: because neither our religious belief nor the scope of the mystery admits either of the Godhead suffering anything or of the Truth belying Itself in anything. The impassible Son of God, therefore, whose perpetually it is with the Father and with the Holy Spirit to be what He is in the one essence of the Unchangeable Trinity, when the fullness of time had come which had been fore-ordained by an eternal purpose, and promised by the prophetic significance of words and deeds, became man not by conversion of His substance but by assumption of our nature, and "came to seek and to save that which was lost6 ." But He came not by local approach nor by bodily motion, as if to be present where He had been absent, or to depart where He had come: but He came to be manifested to onlookers by that which was visible and common to others, receiving, that is to say, human flesh and soul in the Virgin mother's womb, so that, abiding in the form of God, He united to Himself the form of a slave, and the likeness of sinful flesh, whereby He did not lessen the Divine by the human, but increased the human by the Divine.
For such was the state of all mortals resulting from our first ancestors that, after the transmission of original sin to their descendants, no one would have escaped the punishment of condemnation, had not the Word become flesh and dwelt in us, that is to say, in that nature which belonged to our blood and race. And accordingly, the Apostle says: "As by one man's sin (judgment passed) upon all to condemnation, so also by one man's righteousness (it) passed upon all to justification of life. For as by one man's disobedience many were made sinners, so also by one man's obedience shall many be made righteous7 ;" and again, "For because by man (came) death, by man also (came) the resurrection of the dead. And as in Adam all die, so also in Christ shall all be made alive8 ." All they to wit who though they be born in Adam, yet are found reborn in Christ, having a sure testimony both to their justification by grace, and to Christ's sharing in their nature9 ; for he who does not believe that God's only-begotten Son did assume our nature in the womb of the Virgin-daughter of David, is without share in the Mystery of the Christian religion, and, as he neither recognizes the Bridegroom nor knows the Bride, can have no place at the wedding-banquet. For the flesh of Christ is the veil of the Word, wherewith every one is clothed who confesses Him unreservedly. But he that is ashamed of it and rejects it as unworthy, shall have no adornment from Him, and though he present i himself at the Royal feast, and unseasonably join in the sacred banquet, yet the intruder will not be able to escape the King's discernment, but, as the Lord Himself asserted, will be taken, and with hands and feet bound, be cast into outer darkness; where will be weeping and gnashing of teeth10 . Hence whosoever confesses not the human body in Christ, must know that he is unworthy of the mystery of the Incarnation, and has no share in that sacred union of which the Apostle speaks, saying, "For we are His members, of His flesh and of His bones. For this cause a man shall leave father and mother and shall cleave to his wife, and there shall be two in one flesh11 ." And explaining what was meant by this, he added, "This mystery is great, but I speak in respect of Christ and the Church." Therefore, from the very commencement of the human race, Christ is announced to all men as coming in the flesh. In which, as was said, "there shall be two in one flesh," there are undoubtedly two, God and man, Christ and the Church, which issued from the Bridegroom's flesh, when it received the mystery of redemption and regeneration, water and blood flowing from the side of the Crucified. For the very condition of a new creature which at baptism puts off not the covering of true flesh but the taint of the old condemnation, is this, that a man is made the body of Christ, because Christ also is the body of a man12 .
Wherefore we call Christ not God only, as the Manichaean heretics, nor Man only, as the Photinian13 heretics, nor man in such a way that anything should be wanting in Him which certainly belongs to human nature, whether soul or reasonable mind or flesh which was not derived from woman, but made from the Word turned and changed into flesh; which three false and empty propositions have been variously advanced by the three sections of the Apollinarian heretics14 . Nor do we say that the blessed Virgin Mary conceived a Man without Godhead, Who was created by the Holy Ghost and afterwards assumed by the Word, which we deservedly and properly condemned Nestorius for preaching: but we call Christ the Son of God, true God, born of God the Father without any beginning in time, and likewise true Man, born of a human Mother, at the ordained fulness of time, and we say that His Manhood, whereby the Father is the greater, does not in anything lessen that nature whereby He is equal with the Father. But these two natures form one Christ, Who has said most truly both according to His Godhead: "I and the Father are one15 ," and according to His manhood "the Father is greater than I16 ." This true and indestructible Faith, dearly-beloved, which alone makes us true Christians, and which, as we hear with approval, you are defending with loyal zeal and praiseworthy affection, hold fast and maintain boldly. And since, besides God's aid, you must win the favour of catholic Princes also, humbly and wisely make request that the most clement Emperor be pleased to grant our petition, wherein we have asked for a plenary synod to be convened; that by the aid of God's mercy the sound may be increased in courage, and the sick, if they consent to be treated, have the remedy applied. (Dated October 15, in the consulship of the illustrious Asturius and Protogenes, 449.)