Of God and His Creatures2. There is in Christ a perfect divine nature, whereby He is consubstantial with the Father; and a perfect human nature, whereby He is of one species with us. But it is part of the perfection of the divine nature to have a will (B. I, Chap. LXXII); and part of the perfection of human nature to have a will, whereby a man is capable of free choice. There must therefore be two wills in Christ.
3. If in Christ there is no other will than the will of the Word, by parity of reasoning there can be in Him no understanding but the understanding of the Word: thus we are brought back to the position of Apollinaris (Chap. XXXII).
4. If there was only one will in Christ, that must have been the divine will: for the Word could not have lost the divine will, which he had from eternity. But it does not belong to the divine will to merit. Thus then Christ would have merited neither for Himself nor for us by His passion, contrary to the teaching of the Apostle: He was made obedient unto death, therefore hath God exalted him (Phil. ii, 8, 9).
6. In one ordinary man, though he be one in person, there are nevertheless several appetites and operations according to different natural principles. In his rational part there is in him will: in his sensible part there is in him an irascible [thumos] and a concupiscible appetite [epithumêtikon]: and again there is physical tendency following upon physical powers.* In like manner he sees with the eye, hears with the ear, walks with the foot, speaks with the tongue, and understands with the mind, all so many different activities. And the reason is, because activities are not only multiplied according to difference of active subjects, but also according to the difference of the principles whereby one and the same subject works, from which principles also the activities derive their species. But the divine activity differs much more from the human than the natural principles of human nature from one another. There is therefore a difference of will and a difference of operation between the divine and the human nature in Christ, although Christ Himself is one in both natures.
7. The authority of Scripture shows plainly two wills in Christ: Not to do my will, but the will of Him that sent me (John vi, 38): Not my will but thine be done (Luke xxii, 42). These texts show that Christ had a will of His own, besides the will of His Father. On the other hand there was a will common to Him with the Father: for Father and Son have one will, as they have one nature. There are then in Christ two wills.
8. And in like manner of operations, or activities, -- there was in Christ one operation common to Him with the Father, of which He says: Whatsoever things the Father doeth, the same the Son doeth also (John v, 19); and there was in Him another operation which attached not to the Father, as sleeping, hungering, eating, and the like things that Christ did or suffered in His humanity, as the Evangelists record (Mark iv, 38; xi, 12; ii, 16).
Monothelism appears to have sprung from the inability of its authors to distinguish between what is absolutely one and what is one in subordination to another. They saw that the human will in Christ was altogether subordinate to the divine will, so that Christ willed nothing with His human will otherwise than as the divine will predisposed Him to will.* In like manner Christ wrought nothing in His human nature either in doing or in suffering, except what the divine will arranged, according to the text, I do ever the things that are pleasing to him (John viii, 29). The human operation of Christ gained a divine efficacy by His union with the Divinity, in consequence of which everything that He did or suffered made for salvation: wherefore Dionysius calls the human activity of Christ 'theandric.' Seeing then that the human will and operation of Christ was subordinate to the divine, with a subordination that never failed, they [the Monothelites] judged that there was only one will and operation in Christ; although it is not the same thing to be one by subordination and one absolutely.*
4.35 : Against the Error of Eutyches
4.39 : The Doctrine of Catholic Faith concerning the Incarnation