Reply Obj. 2: The relation of subservience and dominion is based upon action and passion, inasmuch as it belongs to a servant to be moved by the will of his master. Now to act is not attributed to the nature as agent, but to the person, since "acts belong to supposita and to singulars," according to the Philosopher (Metaph. i, 1). Nevertheless action is attributed to the nature as to that whereby the person or hypostasis acts. Hence, although the nature is not properly said to rule or serve, yet every hypostasis or person may be properly said to be ruling or serving in this or that nature. And in this way nothing prevents Christ being subject or servant to the Father in human nature.
Reply Obj. 3: As Augustine says (De Trin. i, 8): "Christ will give the kingdom to God and the Father, when He has brought the faithful, over whom He now reigns by faith, to the vision," i.e. to see the essence common to the Father and the Son: and then He will be totally subject to the Father not only in Himself, but also in His members by the full participation of the Godhead. And then all things will be fully subject to Him by the final accomplishment of His will concerning them; although even now all things are subject to Him as regards His power, according to Matt. 28:18: "All power is given to Me in heaven and in earth." _______________________
SECOND ARTICLE [III, Q. 20, Art. 2]
Whether Christ Is Subject to Himself?
Objection 1: It would seem that Christ is not subject to Himself. For
Cyril says in a synodal letter which the Council of Ephesus (Part I,
ch. xxvi) received: "Christ is neither servant nor master of Himself.
It is foolish, or rather impious, to think or say this." And
Damascene says the same (De Fide Orth. iii, 21): "The one Being,
Christ, cannot be the servant or master of Himself." Now Christ is
said to be the servant of the Father inasmuch as He is subject to
Him. Hence Christ is not subject to Himself.
Obj. 2: Further, servant has reference to master. Now nothing has a relation to itself, hence Hilary says (De Trin. vii) that nothing is like or equal to itself. Hence Christ cannot be said to be the servant of Himself, and consequently to be subject to Himself.
Obj. 3: Further, "as the rational soul and flesh are one man; so God and man are one Christ," as Athanasius says (Symb. Fid.). Now man is not said to be subject to himself or servant to himself or greater than himself because his body is subject to his soul. Therefore, Christ is not said to be subject to Himself because His Manhood is subject to His Godhead.
On the contrary, Augustine says (De Trin. i, 7): "Truth shows in this way" (i.e. whereby the Father is greater than Christ in human nature) "that the Son is less than Himself."
Further, as he argues (De Trin. i, 7), the form of a servant was so taken by the Son of God that the form of God was not lost. But because of the form of God, which is common to the Father and the Son, the Father is greater than the Son in human nature. Therefore the Son is greater than Himself in human nature.
Further, Christ in His human nature is the servant of God the Father, according to John 20:17: "I ascend to My Father and to your Father to My God and your God." Now whoever is the servant of the Father is the servant of the Son; otherwise not everything that belongs to the Father would belong to the Son. Therefore Christ is His own servant and is subject to Himself.