34 But if impiety has assumed to itself that because he says, The same Lord and the same God, they are not in unity of nature, I will support this interpretation with what you deem still stronger arguments. For the same Apostle says, But for us there is one God, the Father, of Whom are all things, and we in Him, and one Lord Jesus Christ, through Whom are all things, and we through Him. And again, One Lord, one faith, one baptism, one God and Father of all, Who is both through all, and in us all. By these words one God and one Lord it would seem that to God only is attributed, as to one God, the property of being God; since the property of oneness does not admit of partnership with another.
Verily how rare and hard to attain are such spiritual gifts! How truly is the manifestation of the Spirit seen in the bestowal of such useful gifts! And with reason has this order in the distribution of graces been appointed, that the foremost should be the word of wisdom; for true it is, And no one can call Jesus Lord but in the Holy Spirit, because but through this word of wisdom Christ could not be understood to be Lord; that then there should follow next the word of understanding, that we might speak with understanding what we know, and might know the word of wisdom; and that the third gift should consist of faith, seeing that those leading and higher graces would be unprofitable gifts did we not believe that He is God.
So that in the true sense of this greatest and most noble utterance of the Apostle no heretics possess either the word of wisdom or the word of knowledge or the faith of religion, inasmuch as wilful wickedness, being incapable of understanding, is void of knowledge of the word and of genuineness of faith. For no one utters what he does not know; nor can he believe that which he cannot utter; and thus when the Apostle preached one God, a proselyte as He was from the Law, and called to the gospel of Christ, he has attained to the confession of a perfect faith.
And lest the simplicity of a seemingly unguarded statement might afford heretics any opportunity for denying through the preaching of one God the birth of the Son, the Apostle has set forth one God while indicating His peculiar attribute in these words, One God the Father, of Whom are all things, and we in Him, in order that He Who is God might also be acknowledged as Father. Afterwards, inasmuch as this bare belief in one God the Father would not suffice for salvation, he added, And one, our Lord Jesus Christ, through Whom are all things, and we through Him, showing that the purity of saving faith consists in the preaching of one God and one Lord, so that we might believe in one God the Father and one Lord Jesus Christ.
For he knew full well how our Lord had said, For this is the will of My Father, that every one that sees the Son and believes in Him should have eternal life. But in fixing the order of the Church's faith, and basing our faith upon the Father and the Son, he has uttered the mystery of that indivisible and indissoluble unity and faith in the words one God and one Lord.
Source: On the Trinity (New Advent)