24. Since the Word is from God, He must be Son. Since the Son is from everlasting, He must be the Word; else either He is superior to the Word, or the Word is the Father. Texts of the New Testamentwhich state the unity of the Son with the Father; therefore the Son is the Word. Three hypotheses refuted— 1. That the Man is the Son; 2. That the Word and Man together are the Son; 3. That the Word became Son on His incarnation. Texts of the Old Testamentwhich speak of the Son. If they are merely prophetical, then those concerning the Word may be such also
21 And what more does the Word contribute to our salvation than the Son, if, as they hold, the Son is one, and the Word another? For the command is that we should believe, not in the Word, but in the Son. For John says, 'He that believes in the Son, has everlasting life; but he that believes not the Son, shall not see life.' And Holy Baptism, in which the substance of the whole faith is lodged, is administered not in the Word, but in Father, Son, and Holy Ghost. If then, as they hold, the Word is one and the Son another, and the Word is not the Son, Baptism has no connection with the Word. How then are they able to hold that the Word is with the Father, when He is not with Him in the giving of Baptism? But perhaps they will say, that in the Father's Name the Word is included? Wherefore then not the Spirit also? Or is the Spirit external to the Father? And the Man indeed (if the Word is not Son) is named after the Father, but the Spirit after the Man? And then the Monad, instead of dilating into a Triad, dilates according to them into a Tetrad, Father, Word, Son, and Holy Ghost. Being brought to shame on this ground, they have recourse to another, and say that not the Man by Himself whom the Lord bore, but both together, the Word and the Man, are the Son; for both joined together are named Son, as they say. Which then is cause of which? And which has made which a Son? Or, to speak more clearly, is the Word a Son because of the flesh? Or is the flesh called Son because of the Word? Or is neither the cause, but the concurrence of the two? If then the Word be a Son because of the flesh, of necessity the flesh is Son, and all those absurdities follow which have been already drawn from saying that the Man is Son. But if the flesh is called Son because of the Word, then even before the flesh the Word certainly, being such, was Son. For how could a being make other sons, not being himself a son, especially when there was a father? If then He makes sons for Himself, then is He Himself Father; but if for the Father, then must He be Son, or rather that Son, by reason of Whom the rest are made sons.
22. For if, while He is not Son, we are sons, God is our Father and not His. How then does He appropriate the name instead, saying, 'My Father,' and 'I from the Father?' for if He be common Father of all, He is not His Father only, nor did He alone come out from the Father. But he says, that He is sometimes called our Father also, because He has Himself become partaker in our flesh. For on this account the Word has become flesh, that, since the Word is Son, therefore, because of the Son dwelling in us, He may be called our Father also; for 'He sent forth,' says Scripture, 'the Spirit of His Son into our hearts, crying, Abba, Father.' Therefore the Son in us, calling upon His own Father, causes Him to be named our Father also. Surely in whose hearts the Son is not, of them neither can God be called Father. But if because of the Word the Man is called Son, it follows necessarily, since the ancients are called sons even before the Incarnation, that the Word is Son even before His sojourn among us; for 'I begot sons,' says Scripture; and in the time of Noah, 'When the sons of God saw,' and in the Song, 'Is not He your Father?' Therefore there was also that True Son, for whose sake they too were sons. But if, as they say again, neither of the two is Son, but it depends on the concurrence of the two, it follows that neither is Son; I say, neither the Word nor the Man, but some cause, on account of which they were united; and accordingly that cause which makes the Son will precede the uniting. Therefore in this way also the Son was before the flesh. When this then is urged, they will take refuge in another pretext, saying, neither that the Man is Son, nor both together, but that the Word was Word indeed simply in the beginning, but when He became Man, then He was named Son; for before His appearing He was not Son but Word only; and as the 'Word became flesh,' not being flesh before, so the Word became Son, not being Son before. Such are their idle words; but they admit of an obvious refutation.
23. For if simply, when made Man, He has become Son, the becoming Man is the cause. And if the Man is cause of His being Son, or both together, then the same absurdities result. Next, if He is first Word and then Son, it will appear that He knew the Father afterwards, not before; for not as being Word does He know Him, but as Son. For 'No one knows the Father but the Son.' And this too will result, that He has come afterwards to be 'in the bosom of the Father,' and afterwards He and the Father have become One; and afterwards is, 'He that has seen Me, has seen the Father.' For all these things are said of the Son. Hence they will be forced to say, The Word was nothing but a name. For neither is it He who is in us with the Father, nor whoso has seen the Word, has seen the Father, nor was the Father known to any one at all, for through the Son is the Father known (for so it is written, 'And he to whomsoever the Son will reveal Him'), and, the Word not being yet Son, not yet did any know the Father. How then was He seen by Moses, how by the fathers? For He says Himself in the Kingdoms, 'Was I not plainly revealed to the house of your father?' But if God was revealed, there must have been a Son to reveal, as He says Himself, 'And he to whomsoever the Son will reveal Him.' It is irreligious then and foolish to say that the Word is one and the Son another, and whence they gained such an idea it were well to ask them. They answer, Because no mention is made in the Old Testament of the Son, but of the Word; and for this reason they are positive in their opinion that the Son came later than the Word, because not in the Old, but in the New only, is He spoken of. This is what they irreligiously say; for first to separate between the Testaments, so that the one does not hold with the other, is the device of Manichees and Jews, the one of whom oppose the Old, and the other the New. Next, on their showing, if what is contained in the Old is of older date, and what in the New of later, and times depend upon the writing, it follows that 'I and the Father are One,' and 'Only-begotten,' and 'He that has seen Me has seen the Father,' are later, for these testimonies are adduced not from the Old but from the New.
Source: Four Discourses Against the Arians (New Advent)