(3) Whether Christ by His human operation merited anything for Himself?
(4) Whether He merited anything for us by it? _______________________
FIRST ARTICLE [III, Q. 19, Art. 1]
Whether in Christ There Is Only One Operation of the Godhead and
Manhood?
Objection 1: It would seem that in Christ there is but one operation of the Godhead and the Manhood. For Dionysius says (Div. Nom. ii): "The most loving operation of God is made manifest to us by the supersubstantial Word having taken flesh integrally and truly, and having operated and suffered whatsoever befits His human and Divine operation." But he here mentions only one human and Divine operation, which is written in Greek theandrike, i.e. God-manlike. Hence it seems that there is but one composite operation in Christ.
Obj. 2: Further, there is but one operation of the principal and instrumental agent. Now the human nature in Christ was the instrument of the Divine, as was said above (Q. 7, A. 1, ad 3; Q. 8, A. 1, ad 1; Q. 18, A. 1, ad 2). Hence the operations of the Divine and human natures in Christ are the same.
Obj. 3: Further, since in Christ there are two natures in one hypostasis or person, whatever pertains to the hypostasis or person is one and the same. But operation pertains to the hypostasis or person, for it is only a subsisting suppositum that operates; hence, according to the Philosopher (Metaph. i, 1), acts belong to singulars. Hence in Christ there is only one operation of the Godhead and the Manhood.
Obj. 4: Further, as being belongs to a subsisting hypostasis, so also does operation. But on account of the unity of hypostasis there is only one operation of the Godhead and the (Q. 17, A. 2). Hence, on account of the same unity, there is one operation in Christ.
Obj. [5]: Further, [where there is one thing] operated there is one
operation. But the same thing was operated by the Godhead and the
Manhood, as the healing of the lepers or the raising of the dead.
Hence it seems that in Christ there is but one operation of the
Godhead and the Manhood.
On the contrary, Ambrose says (De Fide ii, 8): "How can the same operation spring from different powers? Cannot the lesser operate as the greater? And can there be one operation where there are different substances?"