¹ Honoured by your office, honoured by your judgment, and compelled by affection, I will speak with you in sincere humility, in benevolent freedom, in genuine charity, and in the word of truth. And although you might have given me reason to remain silent—since, with a kindly and overly trusting heart, you attribute to me nearly as much skill and learning as you have yourself—nevertheless, through the eagerness of your questioning, you have imposed upon me the necessity of responding. In this, I consider myself to be conversing with you in your absence not without trepidation, for when dealing with matters so profound, which surpass both my abilities and yours, it is no less perilous to give an answer than to entrust great mysteries to an unrefined style. Therefore, I ought rather to have reproved my dear friend by remaining silent regarding the things he has spoken too rashly.

² Yet, in deliberating such a weighty matter, in which you have strayed far from the royal road, you should have consulted some men of proven knowledge, those more learned and advanced in years, to whom you could more easily give credence, according to the prophetic injunction: “Ask your father, and he will tell you; your elders, and they will declare it to you”. But without a doubt, whoever seeks a guide, however humble, desires to avoid error. Moreover, in what we do, in what we say, and ultimately in what we presume to commit to writing, we must always seek the fruit and progress of our labour.

³ However, in this little writing that you have deigned to send me, I perceive neither eloquence, nor knowledge, nor reasoning, nor any form of edification from an orderly or deeply considered discourse. Instead, testimonies have been heaped together in great confusion, according to the ease of memory, and they betray the rashness of an incautious heart. The Lord knows that I am astounded, and out of concern for your well-being, I speak these things; may it be that both your questioning and my response serve for our common good.

⁴ In the writings of the holy bishop Augustine, even if something is considered questionable among the most learned men, you should know that nothing from those things you have judged to be condemned has been found reprehensible. Rather, the understanding of faith, especially concerning the two substances or natures of God and man in our Lord and Redeemer, has been received in the Catholic Church not only by the authority of the Fathers but also consecrated by the oracles of the Apostles. Therefore, this statement, which you claim was made to you in a prophetic manner, is certainly not from the Spirit of God and is greatly to be condemned both before God and before men unless you yourself first condemn it.

⁵ Thus, leaving aside other matters, I will briefly, as much as I can in my absence, refute this twofold error, which both arises from heresy and leads into the dangers of heresy. Since the presence of many teachers—not one such as myself—would be necessary for your holy sincerity, I will begin by addressing a claim that is both ignorant and highly dangerous. I will not say that it is merely written, but that it should not even be considered: that a human is the Mother of God. You should know that this descends from the impiety of the Nestorian heresy, for Nestorius did not fear, in his profane boldness, to argue that the Blessed Mary was only the mother of the man, not also of God. For this reason, he was condemned by the strict judgment of the Catholic Church throughout the whole world.

⁶ He says, “It must not be accepted that a human is the Mother of God.” But where, then, is that prophetic or evangelical declaration: “Behold, the virgin shall conceive and bear a son, and they shall call his name Emmanuel, which means ‘God with us’”? And again in the Gospel: “That which will be born of you, the Holy One, shall be called the Son of God”? Where, too, is the authority of the Fathers, received by all the islands and churches, which speaks against Nestorius, saying: “Cursed be he who does not confess that the Son of God, true God, was born of Mary not long ago for our salvation”?

⁷ You went on to say that God and man are of one nature and thus that there is only one substance of God. You would have spoken correctly if you had said this solely concerning the Trinity, where one and the same nature exists under the distinction of three persons. However, when it comes to the incarnation of the assumed man, just as we confess that God and man are one person, so too do we know that there are two substances.

⁸ Whoever asserts that our Lord and Redeemer has only one nature either denies the manhood in the divinity or denies God in the flesh, whereas our redemption was accomplished not by one or the other alone but by both together. If, in this matter, you say that the nature of our faith (if you say “of God”) is only that of our God alone, then by your reasoning, in His own substance of majesty, divinity was crucified. If you say that there is only one nature of God alone, then His majesty itself, in its substance, died and was buried. Yet all these things God underwent not in Himself but in the nature of the man He assumed. For God felt nothing with the feeling of one who suffers but felt with the affection of one who suffers with. He did not feel according to the difference of substance but according to the unity of the person.

⁹ He united both in one and consequently added: “We understand Him to be one and the same, true man and true God.” And he repeated: “We do not in any way doubt that we must confess Him as true man and true God.” Consider also the hymn of the holy bishop and confessor Ambrose, which the Catholic Church sings on the Lord’s Nativity throughout all the regions of Italy and Gaul: “Come forth from your bridal chamber, O giant of twofold substance.”

¹⁰ Seek refuge, then, holy brother, from the error of either extreme. If you say only the nature of God, you impose upon God the condition of suffering and death. But if you say only the nature of man, you take away from God the glory of redemption and deprive the Creator of the power to restore. Listen to how the sacred Scriptures reveal both natures through one person. According to His divine nature, He declares: “I and the Father are one”; according to His human nature, He acknowledges: “The Father is greater than I”. In His heavenly nature, He proclaims: “All that the Father has is mine”; yet in the weakness of His earthly nature, He says: “The Son of Man has nowhere to lay his head”. As a man, He says: “My soul is sorrowful even unto death”; as God, He testifies: “I have power to lay it down, and I have power to take it up again”. According to the nature of His flesh, He hung upon the cross; according to the substance of His divinity, He bestowed paradise and the kingdom of heaven.

¹¹ The Arians, with their hearts darkened and utterly blind to the truth—because arrogance and pride obscure the vision of the mind—attributed to God what belonged to man. They believed that a lesser divinity was speaking where only human weakness was being revealed. By refusing to acknowledge any distinction between the heavenly and the earthly, and by rejecting the two natures in both God and man, they divided the substance of God. And by focusing solely on the words of the man, they lost sight of God, who is the fullness of glory. Thus, whoever denies that the Son of Man is truly God is stained by the impiety of Nestorius, while whoever does not believe in the two natures of the Redeemer is ensnared by the deception of Arius. But we, my dearest brother, must believe in Christ the Lord with a perfect and inseparable distinction: knowing that He is one person, both God and man, yet possessing two natures. Just as body and soul make a man, so divinity and humanity are one Christ.

¹² But you, having been led astray by a twofold error, thought it necessary to write that under the union of two natures, He should not be received in such a way that God is the Father of man and that man is the Mother of God. However, we, confidently and rightly asserting the one person of God and man in Him who was in the beginning and who, in the time of our redemption, was made in the likeness of sinful flesh—that is, in the truth of humanity and the likeness of a sinner—thus testify, I say, to God as the Father of man through the unity of His person, just as, within the same unity, we confess that man is the Mother of God, according to the authority of the Creed, to omit other testimonies, in which we say: “I believe in Jesus Christ, the Son of God, who was conceived by the Holy Spirit, born of the Virgin Mary.” If it is an error to believe in the Lord and Saviour as having one simple substance, then what kind of error is it to assert a double person? For if, in the assumption of the flesh, which God took on in the form of a servant, there were not two substances, then God was not in man, and the person of man was separate from God. Under such a view, you will suddenly see a fourth person appearing from nowhere, and the consequence of such a perverse understanding would be that one would no longer be required to confess the Trinity.

¹³ Listen rather to how the blessed Isaiah, with precise order and careful distinction, sets forth the birth of our Lord and Redeemer: “A child is born to us, a son is given to us”.

¹⁴ Receive, then, the Son of God, begotten in the last days of the world from a virgin mother—nature unaware, but faith uniting in marriage. He was humbled by his own will; the Holy Spirit came upon the Virgin, and in a wondrous way, humanity was filled with God, and God, in his mercy, was transformed into man. Yet, he did not empty himself of the greatness of his glory, but rather, by assuming the condition of a servant, he revealed the compassion of the Lord. “A child is born to us, a son is given to us.”

¹⁵ He was born for us who already existed for himself. He was given from divinity, born from a virgin. He was born so that he might experience death, given so that he might not know a beginning. He was born younger than his mother, given so that his Father was not before him. He was born so that he might die, given so that through him life might be reborn. There, he reigns; here, he is humbled. He rules for himself and serves for me.

¹⁶ A child is born to us, a son is given to us, and dominion has been placed upon his shoulder. The shoulder clearly signifies his humanity; dominion speaks of his hidden divinity. Recognize the two natures united in one person. From us, he took what could suffer; from himself, he gave what could save. From us, he had that by which he could fall; from himself, that by which he could rise. From us, he had that by which he could be held; from himself, that by which he could show mercy. From us, he had that by which he could pay the price for us; from himself, that by which he was in no way a debtor. From us, he had that by which he could be crucified; from himself, that by which he could be glorified. From us, he offered the sacrifice for sin; from himself, he granted the grace of forgiveness.

¹⁷ Thus, his humility is proven by what he took from us; his ascension, by what he is in himself. From us, he offered the sacrifice; from himself, he bestowed the reward. Therefore, the one who is capable of two natures is known as man by his weaknesses and acknowledged as God by his power.

¹⁸ It pains me to extend my discourse on something so obvious with further argument. I know that even by mentioning these things briefly and concisely, I may be carelessly entrusting them either to my letters or to your thoughts. But as long as you humbly submit yourself with sincere concern to the benefit of questioning, I have great hope for the remedy of this error.

¹⁹ I beg you, draw back your foot from this danger before you are swept away by the irreversible torrent of pride. Discipline the right judgment of your mind, which cannot bear the weight of extensive reading nor knows how to dispense the treasure of knowledge—rather, temper it with the effort of labor. Moderate the excessive severity of your abstinence, which even weakens the mind. I believe that this very weakness arises from the same source as your presumption in writing.

²⁰ Return to the royal road; flee from the anxiety that nourishes pride. For we read: “It is not good to eat too much honey”—for knowledge inflates an unfounded understanding more than it builds it up. Be cautious, then, of excessive reading, lest you stir up a dangerous intoxication in a heart too small to contain it, like one who drinks too much wine.

²¹ Never trust your own thoughts, but rather read what is to be imitated rather than rush to write what is to be read. And in your heart, speak to the Lord: “I have hidden Your words in my heart, that I might not sin against You”.

²² If you wish to escape not just external dangers but also those that arise within, know that nothing will benefit you more than to entrust your life to the care of a most worthy abbot, to submit your desires to the rule of a wise elder, and, so that you may overcome the enemy’s snares, to fear yourself.

²³ I thought it best to withhold, or rather suppress, the little writing itself, lest it should fall into the hands and conscience of some other Catholic who loves you less.

²⁴ From this, however, you will be able to recognize that the depths of your heart are sound—if you still listen to me, your guide, with humility and love, heeding my warnings eagerly and willingly, as if I were a free man speaking to you. Before questioning, persuasion might seem to have been rash; but after receiving a response, persistence will appear inexcusable.

²⁵ And if, in all this, you think I should be blamed for anything—though I desire to heal your soul more with severity than with sweetness—remember that the wounds of love are to be preferred over deceitful kisses.