Hilary of Poitiers

If in truth the Word has been made flesh and we in very truth receive the Word made flesh as food from the Lord, are we not bound to believe that he abides in us naturally? [Jesus], born as a man, has assumed the nature of our flesh now inseparable from himself and has joined together the nature of his own flesh to the nature of the eternal Godhead in the sacrament by which his flesh is communicated to us. For in this way we are all one because the Father is in Christ and Christ is in us.… And so, if indeed Christ has taken to himself the flesh of our body, and that man who was born from Mary was indeed Christ, and we indeed receive in a mystery the flesh of his body—and because of this we shall be one, because the Father is in him and he in us—how can a unity of will be maintained, seeing that the special property of nature received through the sacrament is the sacrament of a perfect unity?…As to what we say concerning the reality of Christ’s nature within us, unless we have been taught by him our words are foolish and impious. For he says himself, “My flesh is true food, and my blood is true drink. Those who eat my flesh and drink my blood abide in me, and I in them.” As to the verity of the flesh and blood there is no room left for doubt. For now, both from the declaration of the Lord himself and our own faith, it is truly flesh and truly blood. And these when eaten and drunk enable both that we are in Christ and Christ is in us. Is this not true? Yet those who affirm that Christ Jesus is not truly God are welcome to find it false. He therefore himself is in us through the flesh and we are in him, while together with him our own selves are in God.

(de Trin. ult. med.) Every man, ever born in the flesh, is in a certain sense from God. How then could He say that they were ignorant who He was, and whence He wasa? Because our Lord is here referring to His own peculiar birth from God, which they were ignorant of, because they did not know that He was the Son of God. His very saying then that they did not know whence He was, was telling them whence He was. If they did not know whence He was, He could not be from nothing; for then there would be no whence to be ignorant of. He must therefore be from God. And then not knowing whence He is, was the reason that they did not know who He is. He does not know the Son who does not know His birth from the Father.

(vi. de Trin. ultra med.) I ask however, does the being from Him express a work of creation, or a birth by generation? If a work of creation, then every thing which is created is from Him. And how then does not all creation know the Father, if the Son knows Him, because He is from Him? But if the knowledge of the Father is peculiar to Him, as being from Him, then the being from Him is peculiar to Him also; i. e. the being the true Son of God by nature. So you have then a peculiar knowledge springing from a peculiar generation. To prevent however any heresy applying the being from Him, to the time of His advent, He adds, And He hath sent Me: thus preserving the order of the Gospel sacrament; first announcing Himself born, and then sent.

No one knows the Father; the Son often assures us of this. The reason why he says that no one knows him but himself is because he is from the Father. Is it, I ask, as the result of an act of creation or of a genuine birth that he is from him? If it is an act of creation, then all created things are from God. How then is it that none of them know the Father, when the Son says that the reason why he has this knowledge is that he is from him? If he is created, not born, we shall observe in him a resemblance to other beings who are from God. Since all, on this supposition, are from God, why is he not as ignorant of the Father as the others are? But if this knowledge of the Father is peculiar to him who is from the Father, must not this circumstance also be peculiar to him, that is, that he is from the Father? That is, must he not be the true Son born from the nature of God? For the reason why he alone knows God is because he alone is from God. You observe, then, a knowledge that is peculiar to himself, resulting from a birth that also is peculiar to himself. You recognize that it is not by an act of creative power but through a true birth that he is from the Father. And you realize that this is why he alone knows the Father who is unknown to all other beings that are from him.

The Son of God here was not condemning the devout confidence of those who combine their confession that he is true God, the Son of God, with their own claim to be God’s children. What he is condemning here is the rash presumption of the Jews in claiming God for their Father when they did not love the Son: “If God were your Father, you would surely love me; for I proceeded from God.” … His proceeding is obviously different from his coming, for the two are mentioned side by side in this passage: “For I proceeded and came from God.” In order to elucidate the difference between “I proceeded from God” and “I came,” he further explains, “I did not come on my own, but he sent me.” These words tell us that he is not the source of his own existence. They also tell us that he has proceeded forth a second time from God [in the incarnation] when he was sent by him. But when our Lord says that those who called God their Father ought to love him because he has proceeded from God, there he means that his being born of God was the reason why he should be loved. This proceeding carries back our thoughts to the incorporeal birth, for their claim that God was their Father was supposed to be evident in their loving Christ who was begotten from God. For when the Son says, “Whoever hates me hates my Father as well,” this my is an assertion of his relationship to the Father that no one else has.… No one can worship the Father except those who love the Son. For the one and only reason that he gives for loving the Son is his origin from the Father, not by his advent [i.e. his incarnation] but by his birth [i.e., his eternal generation]. And love for the Father is only possible for those who believe that the Son is from him.

Now seeing that heretics cannot deny these things because they are so clearly stated and understood, they nevertheless pervert them by the most foolish and wicked lies so as afterwards to deny them. For the words of Christ, "I and the Father are one," they endeavour to refer to a mere concord of unanimity, so that there may be in them a unity of will not of nature, that is, that they may be one not by essence of being, but by identity of will...

The Lord prayed on our behalf for our union with God, but God keeps His own unity and abides in it. It is not through any mysterious appointment of God that they are one, but through a birth of nature, for God loses nothing in begetting Him from Himself. They are one, for the things which are not plucked out of His hand are not plucked out of the hand of the Father, for, when He is known, the Father is known, for, when He is seen, the Father is seen, for what He speaks the Father speaks as abiding in Him, for in His works the Father works, for He is in the Father and the Father in Him. This proceeds from no creation but from birth; it is not brought about by will but by power; it is no agreement of mind that speaks, it is nature; because to be created and to be born are not one and the same, any more than to will and to be able; neither is it the same thing to agree and to abide.

Thus we do not deny a unanimity between the Father and the Son,-for heretics are accustomed to utter this falsehood, that since we do not accept concord by itself as the bond of unity we declare Them to be at variance. But let them listen how it is that we do not deny such a unanimity. The Father and the Son are one in nature, honour, power, and the same nature cannot will things that are contrary.

(viii. de Trin. c. 5) The heretics, since they cannot gainsay these words, endeavour by an impious lie to explain them away. They maintain that this unity is unanimity only; a unity of will, not of nature; i. e. that the two are one, not in that they are the same, but in that they will the same. But they are one, not by any economy merely, but by the nativity of the Son's nature, since there is no falling off of the Father's divinity in begetting Him. They are one whilst the sheep that are not plucked out of the Son's hand, are not plucked out of the Father's hand: whilst in Him working, the Father worketh; whilst He is in the Father, and the Father in Him. This unity, not creation but nativity, not will but power, not unanimity but nature accomplisheth. But we deny not therefore the unanimity of the Father and Son; for the heretics, because we refuse to admit concord in the place of unity, accuse us of making a disagreement between the Father and Son. We deny not unanimity, but we place it on the ground of unity. The Father and Son are one in respect of nature, honour, and virtue: and the same nature cannot will different things.

Now seeing that the heretics cannot get around these words because they are so clearly stated and understood, they nevertheless try to explain them away. They maintain that the words "I and the Father are one" refer to a mere union of unanimity only; a unity of will, not of nature, that is, that the two are one not by essence of being but by identity of will. … They make use of the example of our own union with God, as though we were united to the Son and through the Son to the Father by mere obedience and a devout will and not through the true communion of our nature [with his] that is promised to us through the sacrament of the body and blood.…But it is not through any mysterious appointment of God that they are one, but through the birth of the nature, for God loses nothing in begetting the Son from himself. They are one, for the sheep not plucked out of the Son's hand are not plucked out of the hand of the Father.… The Father works in the Son's works, for the Son himself is in the Father and the Father is in him. This proceeds from no creation but from birth. It is not brought about by will but by power. It is not an agreement of mind that speaks but nature that does so. For to be created and to be born are not one and the same any more than to will and to be able are the same; neither is it the same thing to agree and to abide.
Thus we do not deny the unanimity between the Father and the Son—for heretics falsely say that since we do not accept the concord by itself as the bond of unity we declare the Father and the Son to be in disagreement. We do not deny such a unanimity, [but the unanimity results from the unity]. The Father and the Son are one in nature, honor, power, and the same nature cannot will contrary things.