Athanasius Con. Ar., 4.21

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 John 3:36.’ 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.