If Christ is only man, how is it that He says, “Though I bear record of myself, yet my record is true: because I know whence I came, and whither I go; you know not whence I came, and whither I go. You judge after the flesh?” Behold, also He says, that He shall return there whence He bears witness that He came before, as being sent—to wit, from heaven. He came down therefore from whence He came, in the same manner as He goes there from whence He descended. Whence if Christ were only man, He would not have come thence, and therefore would not depart there, because He would riot have come thence.
Moreover, by coming thence, whence as man He could not have come, He shows Himself to have come as God. For the Jews, ignorant and untaught in the matter of this very descent of His, made these heretics their successors, seeing that to them it is said, “You know not whence I come, and whither I go: you judge after the flesh.” As much they as the Jews, holding that the carnal birth of Christ was the only one, believed that Christ was nothing else than man; not considering this point, that as man could not come from heaven, so as that he might return there, He who descended thence must be God, seeing that man could not come thence.
If Christ is only man, how does He say, “You are from below, I am from above; you are of this world, I am not of this world?” But therefore if every man is of this world, and Christ is for that reason in this world, is He only man? God forbid! But consider what He says: “I am not of this world.” Does He then speak falsely when He says “of this world,” if He is only man? Or if He does not speak falsely, He is not of this world; He is therefore not man only, because He is not of this world.
But that it should not be a secret who He was, He declared whence He was: “I,” said He, “am from above,” that is, from heaven, whence man cannot come, for he was not made in heaven. He is God, therefore, who is from above, and therefore He is not of this world; although, moreover, in a certain manner He is of this word: wherefore Christ is not God only, but man also. As reasonably in the way in which He is not of this world according to the divinity of the Word, so He is of this world according to the frailty of the body that He has taken upon Him.
For man is joined with God, and God is linked with man. But on that account this Christ here laid more stress on the one aspect of His sole divinity, because the Jewish blindness contemplated in Christ the aspect alone of the flesh; and thence in the present passage He passed over in silence the frailty of the body, which is of the world, and spoke of His divinity alone, which is not of the world: so that in proportion as they had inclined to believe Him to be only man, in that proportion Christ might draw them to consider His divinity, so as to believe Him to be God, desirous to overcome their incredulity concerning His divinity by omitting in the meantime any mention of His human condition, and by setting before them His divinity alone.
If Christ is man only, how does He say, “I proceeded forth and came from God,” when it is evident that man was made by God, and did not proceed forth from Him? But in the way in which as man He proceeded not from God, thus the Word of God proceeded, of whom it is said, “My heart has uttered forth a good Word;” which, because it is from God, is with reason also with God. And this, too, since it was not uttered without effect, reasonably makes all things: “For all things were made by Him, and without Him was nothing made.” But this Word whereby all things were made (is God).
“And God,” says he, “was the Word.” Therefore God proceeded from God, in that the Word which proceeded is God, who proceeded forth from God. If Christ is only man, how does He say, “If any man shall keep my word, he shall not see death for ever?” Not to see death for ever! What is this but immortality? But immortality is the associate of divinity, because both the divinity is immortal, and immortality is the fruit of divinity. For every man is mortal; and immortality cannot be from that which is mortal.
Therefore from Christ, as a mortal man, immortality cannot arise. “But,” says He, “whosoever keeps my word, shall not see death for ever;”therefore the word of Christ affords immortality, and by immortality affords divinity. But although it is not possible to maintain that one who is himself mortal can make another immortal, yet this word of Christ not only sets forth, but affords immortality: certainly He is not man only who gives immortality, which if He were only man He could not give; but by giving divinity by immortality, He proves Himself to be God by offering divinity, which if He were not God He could not give.
If Christ was only man, how did He say, “Before Abraham was, I Am?” For no man can be before Him from whom he himself is; nor can it be that any one should have been prior to him of whom he himself has taken his origin. And yet Christ, although He is born of Abraham, says that He is before Abraham. Either, therefore, He says what is not true, and deceives, if He was not before Abraham, seeing that He was of Abraham; or He does not deceive, if He is also God, and was before Abraham.
And if this were not so, it follows that, being of Abraham, He could not be before Abraham. If Christ was only man, how does He say, “And I know them, and my sheep follow me; and I give unto them eternal life, and they shall never perish?” And yet, since every man is bound by the laws of mortality, and therefore is unable to keep himself for ever, much more will he be unable to keep another for ever. But Christ promises to give salvation for ever, which if He does not give, He is a deceiver; if He gives, He is God.
But He does not deceive, for He gives what He promises. Therefore He is God who proffers eternal salvation, which man, being unable to keep himself for ever, cannot be able to give to another. If Christ is only man, what is that which He says, “I and the Father are one?” For how can it be that “I and the Father are one,” if He is not both God and the Son?— who may therefore be called one, seeing that He is of Himself, being both His Son, and being born of Him, being declared to have proceeded from Him, by which He is also God; which when the Jews thought to be hateful, and believed to be blasphemous, for that He had shown Himself in these discourses to be God, and therefore rushed at once to stoning, and set to work passionately to hurl stones, He strongly refuted His adversaries by the example and witness of the Scriptures.
“If,” said He, “He called them gods to whom the words of God were given, and the Scriptures cannot be broken, you say of Him whom the Father sanctified, and sent into this world, You blaspheme, because I said, I am the Son of God.” By which words He did not deny Himself to be God, but rather He confirmed the assertion that He was God. For because, undoubtedly, they are said to be gods unto whom the words of God were given, much more is He God who is found to be superior to all these.
And nevertheless He refuted the calumny of blasphemy in a fitting manner with lawful tact. For He wishes that He should be thus understood to be God, as the Son of God, and He would not wish to be understood to be the Father Himself. Thus He said that He was sent, and showed them that He had manifested many good works from the Father; whence He desired that He should not be understood to be the Father, but the Son. And in the latter portion of His defence He made mention of the Son, not the Father, when He said, “You say, You blaspheme, because I said, I am the Son of God.”
Thus, as far as pertains to the guilt of blasphemy, He calls Himself the Son, not the Father; but as pertaining to His divinity, by saying, “I and the Father are one,” He proved that He was the Son of God. He is God, therefore, but God in such a manner as to be the Son, not the Father.
Source: Treatise Concerning the Trinity (New Advent)