The Angelic Doctor Against the Errors of the Greeks - Chapter 12

How the Holy Spirit is to be understood to be the word of the Son.

What Basil says in the third discourse on the Holy Spirit against Eunomius appears to be false: “As the Son is related to the Father, so the Holy Spirit is related to the Son. And this is why the Son is the Word of the Father, and the Holy Spirit is the Word of the Son: upholding the universe, says the Apostle (Heb. 1:3), by the word of his power.”  For as Augustine says in the book on the Trinity,  only the Son is the Word. This is why John also names the Son Word. For at the beginning of his Gospel he says: “In the beginning was the Word” (Jn 1:1). He states also in his first Epistle (5:7): “There are three who give testimony in heaven: the Father, the Word and the Holy Spirit.” Nor does it make any difference whether one translates: Eloquence, in place of Word. For that which one utters is his word. Hence, as the Son alone is the Word in the Godhead, so he alone is the Eloquence.

But it should be noted that sometimes by word of God is meant a discourse divinely inspired and uttered. This is how Basil understands the term when he says that the Holy Spirit is effectively  the word or eloquence of the Son, in so far as the saints inspired by the Holy Spirit have spoken of the Son in accord with what is said in the Gospel of John about the Holy Spirit (16:13): “Whatever he hears, he will speak.” That this is Basil’s mind is clear from what he adds later: “From him the eloquence of the Son for God.”  For the very word of faith uttered by the saints is obviously called the sword of the Spirit.