69. Therefore amid the numerous dangers which threaten the faith, brevity of words must be employed sparingly, lest what is piously meant be thought to be impiously expressed, and a word be judged guilty of occasioning heresy when it has been used in conscientious and unsuspecting innocence. A Catholic about to state that the substance of the Father and the Son is one, must not begin at that point: nor hold this word all important as though true faith did not exist where the word was not used. He will be safe in asserting the one substance if he has first said that the Father is unbegotten, that the Son is born, that He draws His personal subsistence from the Father, that He is like the Father in might, honour and nature, that He is subject to the Father as to the Author of His being, that He did not commit robbery by making Himself equal with God, in whose form He remained, that He was obedient unto death. He did not spring from nothing, but was born. He is not incapable of birth but equally eternal. He is not the Father, but the Son begotten of Him. He is not any portion of God, but is whole God. He is not Himself the source but the image; the image of God born of God to be God. He is not a creature but is God. Not another God in the kind of His substance, but the one God in virtue of the essence of His exactly similar substance. God is not one in Person but in nature, for the Born and the Begetter have nothing different or unlike. After saying all this, he does not err in declaring one substance of the Father and the Son. Nay, if he now denies the one substance he sins.
70. Therefore let no one think that our words were meant to deny the one substance. We are giving the very reason why it should not be denied. Let no one think that the word ought to be used by itself and unexplained. Otherwise the word homoousios is not used in a religious spirit. I will not endure to hear that Christ was born of Mary unless I also hear, In the beginning was the Word, and the Word was God [490] . I will not hear Christ was hungry, unless I hear that after His fast of forty days He said, Man doth not live by bread alone [491] . I will not hear He thirsted unless I also hear Whosoever drinketh of the water that I shall give him shall never thirst [492] . I will not hear Christ suffered unless I hear, The hour is come that the Son of man should be glorified [493] . I will not hear He died unless I hear He rose again. Let us bring forward no isolated point of the divine mysteries to rouse the suspicions of our hearers and give an occasion to the blasphemers. We must first preach the birth and subordination of the Son and the likeness of His nature, and then we may preach in godly fashion that the Father and the Son are of one substance. I do not personally understand why we ought to preach before everything else, as the most valuable and important of doctrines and in itself sufficient, a truth which cannot be piously preached before other truths, although it is impious to deny it after them.
71. Beloved brethren, we must not deny that there is one substance of the Father and the Son, but we must not declare it without giving our reasons. The one substance must be derived from the true character of the begotten nature, not from any division, any confusion of Persons, any sharing of an anterior substance. It may be right to assert the one substance, it may be right to keep silence about it. You believe in the birth and you believe in the likeness. Why should the word cause mutual suspicions, when we view the fact in the same way? Let us believe and say that there is one substance, but in virtue of the true character of the nature and not to imply a blasphemous unity of Persons. Let the oneness be due to the fact that there are similar Persons and not a solitary Person.
72. But perhaps the word similarity may not seem fully appropriate. If so, I ask how I can express the equality of one Person with the other except by such a word? Or is to be like not the same thing as to be equal? If I say the divine nature is one I am suspected of meaning that it is undifferentiated: if I say the Persons are similar, I mean that I compare what is exactly like. I ask what position equal holds between like and one? I enquire whether it means similarity rather than singularity. Equality does not exist between things unlike, nor does similarity exist in one. What is the difference between those that are similar and those that are equal? Can one equal be distinguished from the other? So those who are equal are not unlike. If then those who are unlike are not equals, what can those who are like be but equals?
73. Therefore, beloved brethren, in declaring that the Son is like in all things to the Father, we declare nothing else than that He is equal. Likeness means perfect equality, and this fact we may gather from the Holy Scriptures, And Adam lived two hundred and thirty years, and begat a son according to his own image and according to his own likeness; and called his name Seth [494] . I ask what was the nature of his likeness and image which Adam begot in Seth? Remove bodily infirmities, remove the first stage of conception, remove birth-pangs, and every kind of human need. I ask whether this likeness which exists in Seth differs in nature from the author of his being, or whether there was in each an essence of a different kind, so that Seth had not at his birth the natural essence of Adam? Nay, he had a likeness to Adam, even though we deny it, for his nature was not different. This likeness of nature in Seth was not due to a nature of a different kind, since Seth was begotten from only one father, so we see that a likeness of nature renders things equal because this likeness betokens an exactly similar essence. Therefore every son by virtue of his natural birth is the equal of his father, in that he has a natural likeness to him. And with regard to the nature of the Father and the Son the blessed John teaches the very likeness which Moses says existed between Seth and Adam, a likeness which is this equality of nature. He says, Therefore the Jews sought the more to kill Him, because He not only had broken the Sabbath, but said also that God was His father, making Himself equal with God [495] . Why do we allow minds that are dulled with the weight of sin to interfere with the doctrines and sayings of such holy men, and impiously match our rash though sluggish senses against their impregnable assertions? According to Moses, Seth is the likeness of Adam, according to John, the Son is equal to the Father, yet we seek to find a third impossible something between the Father and the Son. He is like the Father, He is the Son of the Father, He is born of Him: this fact alone justifies the assertion that they are one.
74. I am aware, dear brethren, that there are some who confess the likeness, but deny the equality. Let them speak as they will, and insert the poison of their blasphemy into ignorant ears. If they say that there is a difference between likeness and equality, I ask whence equality can be obtained? If the Son is like the Father in essence, might, glory and eternity, I ask why they decline to say He is equal? In the above creed an anathema was pronounced on any man who should say that the Father was Father of an essence unlike Himself. Therefore if He gave to Him whom He begat without effect upon Himself a nature which was neither another nor a different nature, He cannot have given Him any other than His own. Likeness then is the sharing of what is one's own, the sharing of one's own is equality, and equality admits of no difference [496] . Those things which do not differ at all are one. So the Father and the Son are one, not by unity of Person but by equality of nature.
75. Although general conviction and divine authority sanction no difference between likeness and equality, since both Moses and John would lead us to believe the Son is like the Father and also His equal, yet let us consider whether the Lord, when the Jews were angry with Him for calling God His Father and thus making Himself equal with God, did Himself teach that He was equal with God. He says, The Son can do nothing of Himself, but what He seeth the Father do [497] . He shewed that the Father originates by saying Can do nothing of Himself, He calls attention to His own obedience by adding, but what He seeth the Father do. There is no difference of might, He says He can do nothing that He does not see because it is His nature and not His sight that gives Him power. But His obedience consists in His being able only when He sees. And so by the fact that He has power when He sees, He shews that He does not gain power by seeing but claims power on the authority of seeing. The natural might does not differ in Father and Son, the Son's equality of power with the Father not being due to any increase or advance of the Son's nature but to the Father's example. In short that honour which the Son's subjection retained for the Father belongs equally to the Son on the strength of His nature. He has Himself added, What things soever He doeth, these also doeth the Son likewise [498] . Surely then the likeness implies equality. Certainly it does, even though we deny it: for these also doeth the Son likewise. Are not things done likewise the same? Or do not the same things admit equality? Is there any other difference between likeness and equality, when things that are done likewise are understood to be made the same? Unless perchance any one will deny that the same things are equal, or deny that similar things are equal, for things that are done in like manner are not only declared to be equal but to be the same things.
76. Therefore, brethren, likeness of nature can be attacked by no cavil, and the Son cannot be said to lack the true qualities of the Father's nature because He is like Him. No real likeness exists where there is no equality of nature, and equality of nature cannot exist unless it imply unity, not unity of person but of kind. It is right to believe, religious to feel, and wholesome to confess, that we do not deny that the substance of the Father and the Son is one because it is similar, and that it is similar because they are one.
77. Beloved, after explaining in a faithful and godly manner the meaning of the phrases one substance, in Greek homoousion, and similar substance or homoiousion, and shewing very completely the faults which may arise from a deceitful brevity or dangerous simplicity of language, it only remains for me to address myself to the holy bishops of the East. We have no longer any mutual suspicions about our faith, and those which before now have been due to mere misunderstanding are being cleared away. They will pardon me if I proceed to speak somewhat freely with them on the basis of our common faith.
78. Ye who have begun to be eager for apostolic and evangelical doctrine, kindled by the fire of faith amid the thick darkness of a night of heresy, with how great a hope of recalling the true faith have you inspired us by consistently checking the bold attack of infidelity! In former days it was only in obscure corners that our Lord Jesus Christ was denied to be the Son of God according to His nature, and was asserted to have no share in the Father's essence, but like the creatures to have received His origin from things that were not. But the heresy now bursts forth backed by civil authority, and what it once muttered in secret it has of late boasted of in open triumph. Whereas in former times it has tried by secret mines to creep into the Catholic Church, it has now put forth every power of this world in the fawning manners of a false religion. For the perversity of these men has been so audacious that when they dared not preach this doctrine publicly themselves, they beguiled the Emperor to give them hearing. For they did beguile an ignorant sovereign so successfully that though he was busy with war he expounded their infidel creed, and before he was regenerate by baptism imposed a form of faith upon the churches. Opposing bishops they drove into exile. They drove me also to wish for exile, by trying to force me to commit blasphemy. May I always be an exile, if only the truth begins to be preached again! I thank God that the Emperor, through your warnings, acknowledged his ignorance, and through these your definitions of faith came to recognize an error which was not his own but that of his advisers. He freed himself from the reproach of impiety in the eyes of God and men, when he respectfully received your embassy, and after you had won from him a confession of his ignorance, shewed his knowledge of the hypocrisy of the men whose influence brought him under this reproach.