8 For they attempt, by praising the Godhead of the Father only, to deprive the Son of His Divinity, pleading that it is written, Hear, O Israel, the Lord your God is One, and that the Lord repeats this in His answer to the doctor of the Law who asked Him what was the greatest commandment in the Law;— Hear, O Israel, the Lord your God is One. Again, they say that Paul proclaims, For there is One God, and One Mediator between God and men. And furthermore, they insist that God alone is wise, in order to leave no wisdom for the Son, relying upon the words of the Apostle, Now to Him that is able to establish you according to my gospel and the preaching of Jesus Christ, according to the revelation of the mystery which has been kept in silence through age-long times, but now is manifested through the scriptures of the prophets according to the commandment of the eternal God Who is made known unto all nations unto obedience of faith; to the only wise God, through Jesus Christ, to Whom be glory for ever and ever. They argue also that He alone is true, for Isaiah says, They shall bless You, the true God, and the Lord Himself has borne witness in the Gospel, saying, And this is life eternal that they should know You, the only true God, and Jesus Christ Whom You have sent. Again they reason that He alone is good, to leave no goodness for the Son, because it has been said through Him, There is none good save One, even God; and that He alone has power, because Paul has said, Which in His own times He shall show to us, Who is the blessed and only Potentate, the King of kings and Lord of lords. And further, they profess themselves certain that in the Father there is no change nor turning, because He has said through the prophet, I am the Lord your God, and I am not changed, and the apostle James, With Whom there is no change; certain also that He is the righteous Judge, for it is written, God is the righteous Judge, strong and patient; that He cares for all, because the Lord has said, speaking of the birds, And your heavenly. Father feeds them, and, Are not two sparrows sold for a farthing? And not one of them falls upon the ground without the will of your Father; but the very hairs of your head are numbered. They say that the Father has prescience of all things, as the blessed Susanna says, O eternal God, that know secrets, and know all things before they be; that He is incomprehensible, as it is written, The heaven is My throne, and the earth is the footstool of My feet. What house will you build Me, or what is the place of My rest? For these things has My hand made, and all these things are mine; that He contains all things, as Paul bears witness, For in Him we live and move and have our being, and the psalmist, Whither shall I go from Your Spirit, and whither shall I fly from Your face? If I climb up into heaven, You are there; if I go down to hell, You are present. If I take my wings before the light and dwell in the uttermost parts of the sea, even there Your hand shall lead me and Your right hand shall hold me; that He is without body, for it is written, For God is Spirit, and they that worship Him must worship in spirit and in truth; that He is immortal and invisible, as Paul says, Who only has immortality, and dwells in light unapproachable, whom no man has seen nor can see, and the Evangelist, No one has seen God at any time, except the Only-begotten Son, which is in the bosom of the Father; that He alone abides eternally unborn, for it is written, I Am That I Am, and Thus shall you say to the children of Israel, I Am has sent me unto you, and through Jeremiah, O Lord, Who art Lord.
Source: On the Trinity (New Advent)