Thus I was compelled to write when I read the letters of your holiness to the most pious and sacred archbishop Domnus, for there was contained in them the statement that certain men have come to the illustrious city administered by your holiness, and have accused me of dividing the one Lord Jesus Christ into two sons, and this when preaching at Antioch, where innumerable hearers swell the congregation. I wept for the men who had the hardihood to contrive the vain calumny against me. But I grieved, and, my Lord, forgive me, forced as I am by pain to speak, that your pious excellency did not reserve one ear unbiassed for me instead of believing the lies of my accusers. Yet they were but three or four or about a dozen while I have countless hearers to testify to the orthodoxy of my teaching. Six years I continued teaching in the time of Theodotus bishop of Antioch, of blessed and sacred memory, who was famous alike for his distinguished career and for his knowledge of the divine doctrines. Thirteen years I taught in the time of bishop John of sacred and blessed memory, who was so delighted at my discourses as to raise both his hands and again and again to start up: your holiness in your own letters has borne witness how, brought up as he was from boyhood with the divine oracles, the knowledge which he had of the divine doctrines was most exact. Besides these this is the seventh year of the most pious lord archbishop Domnus.  Up to this present day, after the lapse of so long a time, not one of the pious bishops, not one of the devout clergy has ever at any time found any fault with my utterances. And with how much gratification Christian people hear our discourses your godly excellency can easily learn, alike from those who have travelled thence hither, and from those who reached your city from us.
All this I say not for the sake of boasting, but because I am forced to defend myself. It is not the fame of my sermons to which I am calling attention; it is their orthodoxy alone. Even the great teacher of the world who is wont to style himself last of saints and first of sinners, that he might stop the mouths of liars was compelled to set forth a list of his own labours; and in shewing that this account of his sufferings was of necessity, not of free will, he added "I am become a fool in glorying; ye have compelled me."  I own myself wretched -- aye thrice wretched. I am guilty of many errors. Through faith alone I look for finding some mercy in the day of the Lord's appearing. I wish and I pray that I may follow the footprints of the holy Fathers, and I earnestly desire to keep undefiled the evangelic teaching which was in sum delivered to us by the holy Fathers assembled in council at the Bithynian Nicæa. I believe that there is one God the Father and one Holy Ghost proceeding from the Father:  so also that there is one Lord Jesus Christ, only begotten Son of God, begotten of the Father before all ages, brightness of His glory and express image of the Father's person,  on account of man's salvation, incarnate and made man and born of Mary the Virgin in the flesh. For so are we taught by the wise Paul "Whose are the Fathers and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen,"  and again "Concerning His Son Jesus Christ our Lord which was made of the seed of David according to the flesh and declared to be the Son of God with power according to the spirit of holiness."  On this account we also call the holy Virgin "Theotokos,"  and deem those who object to this appellation to be alienated from true religion.
In the same manner we call those men corrupt and exclude them from the assembly of the Christians, who divide our one Lord Jesus Christ into two persons or two sons or two Lords, for we have heard the very divine Paul saying "One Lord, one faith, one baptism"  and again "One Lord Jesus Christ by Whom are all things"  and again "Jesus Christ the same yesterday and to-day and for ever"  and in another place -- "He that descended is the same also that ascended up far above all heavens."  And countless other passages of this kind may be found in the Apostle's writings, proclaiming the one Lord.
So too the divine Evangelist exclaims, "And the Word was made flesh and dwelt among us and we beheld His glory, the glory as of the only begotten of the Father, full of grace and truth." 
And his namesake exclaimed, "After me cometh one who is preferred before me for He was before me."  And when he had shewn one person, he expressed both the divine and the human, for the words "man" and "comes" are human, but the phrase "He was before me" expresses the divine. But nevertheless he did not recognise a distinction between Him who came after and Him who was before, but owned the same being to be eternal as God, but born man, after himself, of the Virgin.
Thus too, the thrice blessed Thomas, when he had put his hand on the flesh of the Lord, called Him Lord and God, saying "My Lord and my God."  For through the visible nature he discerned the invisible.
So do we know no difference between the same flesh and the Godhead but we own God the Word made man to be one Son.
These lessons we have learnt alike from the holy Scripture and from the holy Fathers who have expounded it, Alexander and Athanasius, loud voiced heralds of the truth, who have been ornaments of your apostolic see; from Basil and from Gregory and the rest of the lights of the world; and that, in our endeavour to shut the mouths of them that dare to oppose the blessed Theophilus and Cyril, we use their works, our own writings testify. For we are most anxious by the medicines supplied by very holy men to heal them that deny the distinction between the Lord's flesh and the Godhead, and who maintain at one moment that the divine nature was changed into flesh, and at another that the flesh was transmuted into nature of Godhead.
For they clearly instruct us in the distinction between the two natures, and proclaim the immutability of the divine nature, calling the flesh of the Lord divine as being made flesh of God the Word; but the doctrine that it was transmuted into nature of Godhead they repudiate as impious.
I think that your excellency is well aware that Cyril of blessed memory often wrote to me, and when he sent his books against Julian to Antioch, and in like manner his book on the scapegoat, he asked the blessed John, bishop of Antioch, to shew them to the great teachers of the East; and in compliance with this request the blessed John sent us the books. I read them with admiration, and I wrote to Cyril of blessed memory; and he wrote back to me praising my exactitude and kindness. This letter I have preserved.
That I twice subscribed the writings of John of blessed memory concerning Nestorius my own hand bears witness, but this is the kind of thing whispered about me by men who try to conceal their own unsoundness by calumniating me.
Therefore I implore your holiness to turn your back on the liars; to give heed to the Church's quiet and either to heal by salutary medicines them that are trying to destroy the doctrines of the truth, or, if they refuse to accept your treatment, to expel them from the fold, to the end that the sheep may be spared from contagion. I beg you to give me your customary salutation. That I have written you my true sentiments is proved by my works on the holy Scriptures and against the Arians and Eunomians.
I will in addition write yet a brief word. If any one refuses to confess the holy Virgin to be "Theotokos," or calls our Lord Jesus Christ bare man, or divides into two sons Him who is one only begotten and first born of every creature, I pray that he may fall from hope in Christ, and let all the people say amen, amen.
Now that I have thus spoken, deign, my lord, to give me your sacred prayers, and to cheer me by a letter in reply telling me that your holiness has turned your back on my accusers.
I and my household salute all thy brotherhood in piety in Christ.
 Domnus succeeded his Uncle John at Antioch in 441.  2 Corinthians 12:11  The first formal insertion of the addition filioque is said to be in a Creed put forth at a council of Toledo about a.d. 400. At the third council of Toledo a.d. 589, the Nicæno-Constantinopolitan Creed was promulgated with the addition--"ex Patre et Filio procedentem."  Hebrews 1:3  Romans 9:5  Romans 1:3, 4  cf. note on page 213.  Ephesians 4:5  1 Corinthians 8:6  Hebrews 13:8  Ephesians 4:10  John 1:14  John 1:15  John 20:28
 2 Corinthians 12:11
 The first formal insertion of the addition filioque is said to be in a Creed put forth at a council of Toledo about a.d. 400. At the third council of Toledo a.d. 589, the Nicæno-Constantinopolitan Creed was promulgated with the addition--"ex Patre et Filio procedentem."
 Hebrews 1:3
 Romans 9:5
 Romans 1:3, 4
 cf. note on page 213.
 Ephesians 4:5
 1 Corinthians 8:6
 Hebrews 13:8
 Ephesians 4:10
 John 1:14
 John 1:15
 John 20:28