Chapter 8.
Christ, so far as He is true Son of God, has no Lord, but only so far as He is Man; as is shown by His words in which He addressed at one time the Father, at another the Lord. How many heresies are silenced by one verse of Scripture! We must distinguish between the things that belong to Christ as Son of God or as Son of David. For under the latter title only must we ascribe it to Him that He was a servant. Lastly, he points out that many passages cannot be taken except as referring to the Incarnation.
99. Wherefore also it is plain how He calls Him Lord, Whom He knew as Father. For He says: “I confess to You, Father, Lord of heaven and earth.” First Wisdom spoke of His own Father, and then proclaimed Him Lord of creation. For this reason the Lord shows in His Gospel that no lordship is exercised where there is a true offspring, saying: “What do you think of Christ? Whose Son is He? They say unto Him, The son of David. Jesus says to them, How then does David in spirit call Him Lord, saying: The Lord said unto my Lord: Sit on My right hand”? Then he added: “If David in spirit then call Him Lord, how is He his son? And no man was able to answer Him a word.”
100. With what care did the Lord provide for the faith in this witness because of the Arians! For He did not say: “The spirit calls Him Lord,” but that “David spoke in spirit;” in order that men might believe that as He is his, that is, David's son according to the flesh, so also He is his Lord and God according to His Godhead. You see, then, that there is a distinction between the titles that are used of relationship and of lordship.
101. And rightly did the Lord speak of His own Father, but of the Lord of heaven and earth; so that you, when you read of the Father and the Lord, may understand it is the Father of the Son, and the Lord of Creation. In the one title rests the claim of nature, in the other the authority to rule. For taking on Himself the form of a servant, He calls Him Lord, because He has submitted to service; being equal to Him in the form of God, but being a servant in the form of His body: for service is the due of the flesh, but lordship is the due of the Godhead. Wherefore also the Apostle says: “The God of our Lord Jesus Christ, the Father of glory,” that is, terming Him God of the adoption of humanity but the Father of glory. Did God have two Sons, Christ and Glory? Certainly not. Therefore if there is one Son of God, even Christ, Christ is Glory. Why do you strive to belittle Him who is the glory of the Father?
102. If then the Son is glory, and the Father is glory (for the Father of glory cannot be anything else than glory), there is no separation of glories, but glory is one. Thus glory is referred to its own proper nature, but lordship to the service of the body that was assumed. For if the flesh is subject to the soul of a just man as it is written: “I chastise my body and bring it into subjection;” how much more is it subject to the Godhead, of Which it is said: “For all things serve You”?
103. By one question the Lord has shut out both Sabellians and Photinians and Arians. For when He said that the Lord spoke to the Lord, Sabellius is set aside, who will have it that the same Person is both Father and Son. Photinus is set aside, who thinks of Him merely as man; for none could be Lord of David the King, but He Who is God, for it is written: “You shall worship the Lord your God, and Him only shall you serve.” Would the prophet who ruled under the Law act contrary to the Law? Arius is set aside, who hears that the Son sits on the right hand of the Father; so that if he argues from human ways, he refutes himself, and makes the poison of his blasphemous arguments to flow back upon himself. For in interpreting the inequality of the Father and the Son by the analogy of human habits (wandering from the truth in either case), he puts Him first Whom he makes little of, confessing Him to be the First, Whom he hears to be at the right hand. The Manichæan also is set aside, for he does not deny that He is the Son of David according to the flesh, Who, at the cry of the blind men, “Jesus, Son of David, have mercy on us,” was pleased at their faith and stood and healed them. But He does deny that this refers to His eternity, if He is called Son of David alone by those who are false.
104. For “Son of God” is against Ebion, “Son of David,” is against the Manichees; “Son of God” is against Photinus, “Son of David” is against Marcion; “Son of God” is against Paul of Samosata, “Son of David” is against Valentinus; “Son of God” is against Arius and Sabellius, the inheritors of heathen errors. “Lord of David” is against the Jews, who beholding the Son of God in the flesh, in impious madness believed Him to be only man.
105. But in the faith of the Church one and the same is both Son of God the Father and Son of David. For the mystery of the Incarnation of God is the salvation of the whole of creation, according to that which is written: “That without God He should taste death for every man;” that is, that every creature might be redeemed without any suffering at the price of the blood of the Lord's Divinity, as it stands elsewhere: “Every creature shall be delivered from the bondage of corruption.”
106. It is one thing to be named Son according to the divine Substance, it is another thing to be so called according to the adoption of human flesh. For, according to the divine Generation, the Son is equal to God the Father; and, according to the adoption of a body, He is a servant to God the Father. “For,” it says, “He took upon Him the form of a servant.” The Son is, however, one and the same. On the other hand, according to His glory, He is Lord to the holy patriarch David, but his Son in the line of actual descent, not abandoning anything of His own, but acquiring for Himself the rights that go with the adoption into our race.
107. Not only does He undergo service in the character of man by reason of His descent from David, but also by reason of His name, as it is written: “I have found David My Servant;” and elsewhere: “Behold I will send unto you My Servant, the Orient is His name.” And the Son Himself says: “Thus says the Lord, that formed Me from the womb to be His servant, and said unto Me: It is a great thing for You to be called My Servant. Behold I have set You up for a witness to My people, and a light to the Gentiles, that You may be for salvation unto the ends of the earth.” To whom is this said, if not to Christ? Who being in the form of God, emptied Himself and took upon Him the form of a servant. But what can be in the form of God, except that which exists in the fullness of the Godhead?
108. Learn, then, what this means: “He took upon Him the form of a servant.” It means that He took upon Him all the perfections of humanity in their completeness, and obedience in its completeness. And so it says in the thirtieth Psalm: “You have set my feet in a large room. I am made a reproach above all mine enemies. Make Your face to shine upon Your servant.” “Servant” means the Man in whom He was sanctified; it means the Man in whom He was anointed; it means the Man in whom He was made under the law, made of the Virgin; and, to put it briefly, it means the Man in whose person He has a mother, as it is written: “O Lord, I am Your Servant, I am Your Servant, and the Son of Your hand-maid;” and again: “I am cast down and sore humbled.”
Source: On the Christian Faith (De fide) (New Advent)