Let no one then foolishly suppose that the Christ is any other than the only begotten Son. Let us not imagine ourselves wiser than the gift of the Spirit. Let us hear the words of the great Peter, “You are the Christ, the Son of the living God.” Let us hear the Lord Christ confirming this confession, for “On this rock,” He says, “I will build my church and the gates of Hell shall not prevail against it.” Wherefore too the wise Paul, most excellent master builder of the churches, fixed no other foundation than this. “I,” he says, “as a wise master builder have laid the foundation, and another builds thereon. But let every man take heed how he builds thereon. For other foundation can no man lay than that is laid, which is Jesus Christ.” How then can they think of any other foundation, when they are bidden not to fix a foundation, but to build on that which is laid? The divine writer recognises Christ as the foundation, and glories in this title, as when he says, “I am crucified with Christ: nevertheless I live; yet not I but Christ lives in me.” And again “To me to live is Christ and to die is gain,” and again “For I determined not to know anything among you save Jesus Christ and Him crucified.” And a little before he says, “But we preach Christ crucified to the Jews a stumbling-block and to the Greeks foolishness, but unto them which are called both Jews and Greeks, Christ the power of God and the wisdom of God.” And in his Epistle to the Galatians he writes, “But when it pleased God who separated me from my mother's womb and called me by His grace to reveal His Son in me that I might preach Him among the heathen.” But when writing to the Corinthians he does not say we preach “the Son” but “Christ crucified,” herein doing no violence to his commission, but recognising the same to be Jesus, Christ, Lord, only begotten, and God the Word. For the same reason too at the beginning of his letter to the Romans he calls himself “servant of Jesus Christ” and describes himself as “separated unto the gospel of God, which He had promised afore by His prophets in the Holy Scriptures, concerning His Son Jesus Christ our Lord, which was made of the seed of David according to the flesh; and declared to be the Son of God with power” and so on. He calls the same both Jesus Christ, and Son of David, and Son of God, as God and Lord of all, and yet in the middle of his epistle, after making mention of the Jews, he adds, “whose are the fathers, and of whom as concerning the flesh Christ came, who is over all God blessed for ever, amen.” Here he says that He who according to the flesh derived His descent from the Jews is eternal God and is praised by the right minded as Lord of all created things. The same teaching is given us in the Apostle's words to the excellent Titus “Looking for that blessed hope, and the glorious appearing of the great God and our Saviour Jesus Christ.” Here he calls the same both Saviour, and great God, and Jesus Christ. And in another place he writes, “In the kingdom of Christ and of God.” Moreover the chorus of the angels announced to the shepherds “Unto you is born this day in the city of David...Christ the Lord.”
But to men who meditate on God's law day and night, it is indeed needless to write all the proofs of this kind; the above are sufficient to persuade even the most obstinate opponents not to divide the divine titles. One point, however, I cannot endure to omit. He is alleged to have said that there are many Christs but one Son. Into this error I suppose he fell through ignorance. For if he had read the divine Scripture, he would have known that the title of the Son has also been bestowed by our bountiful Lord on many. The lawgiver Moses, the writer of the ancient history, says “And the sons of God saw the daughters of men that they were fair and they took them wives of them,” and the God of all Himself said to this Prophet “You shall say unto Pharaoh, Israel is my son even my first-born.” In the great song he says “Rejoice O you nations with His people and let all the sons of God be strong in Him;” and by the mouth of the prophet Isaiah He says “I have nourished and brought up sons (children) and they have rebelled against me;” and through the thrice blessed David “I have said you are gods and all of you are children of the Most High,” and to the Romans the wise Paul wrote in this manner, “For as many as are led by the Spirit of God, they are the sons of God. For you have not received the spirit of bondage again to fear; but you have received the spirit of adoption, whereby we cry, Abba, Father. For the Spirit itself bears witness with our spirit, that we are the children of God. And if children, then heirs; heirs of God and joint-heirs with Christ: if so be that we suffer with Him that we may be also glorified together;” and to the Galatians he writes “And because you are sons God has sent forth the spirit of His Son into your hearts, crying, Abba, Father. Wherefore you are no more a servant but a son; and if a son then an heir of God through Jesus Christ.” The lesson he gives to the Ephesians is “in love having predestinated us into the adoption of children by Jesus Christ to Himself.”
If then, because the name of the Christ is common, we ought not to glorify the Christ as God, we shall equally shrink from worshipping Him as Son, since this also is a name which has been bestowed upon many. And why do I say the Son? The very name of God itself has been given by God to many. “The Lord the God of gods has spoken and called the earth.” And “I have said You are gods,” and “You shall not revile the gods.” Many too have appropriated this name to themselves. The dæmons who have deceived mankind have given this title to idols; whence Jeremiah exclaims, “The gods that have not made the heavens and the earth even they shall perish from the earth and from under these heavens;” and again “They made to themselves gods of silver and gods of gold;” and the prophet Isaiah when he had mocked the making of the idols, and said “He burns part thereof in the fire with part thereof he eats flesh he warms himself and says Aha I am warm I have seen the fire,” went on “and the residue thereof he makes a god and falls down unto it and says 'Deliver me for you are my god'” and so the prophet laments over them and says “Know that their heart is ashes.” And the Psalmist David has taught us to sing “For all the gods of the nations are idols, but the Lord made the heavens.”
But this common use of titles gives no offense to men who are instructed in true religion. We are aware that the dæmons have falsely bestowed upon themselves and on idols the divine name, while the saints have received this honour of free grace.
Source: Letters (New Advent)