I answer that, Some placed only one will in Christ; but they seem to have had different motives for holding this. For Apollinaris did not hold an intellectual soul in Christ, but maintained that the Word was in place of the soul, or even in place of the intellect. Hence since "the will is in the reason," as the Philosopher says (De Anima iii, 9), it followed that in Christ there was no human will; and thus there was only one will in Him. So, too, Eutyches and all who held one composite nature in Christ were forced to place one will in Him. Nestorius, too, who maintained that the union of God and man was one of affection and will, held only one will in Christ. But later on, Macarius, Patriarch of Antioch, Cyrus of Alexandria, and Sergius of Constantinople and some of their followers, held that there is one will in Christ, although they held that in Christ there are two natures united in a hypostasis; because they believed that Christ's human nature never moved with its own motion, but only inasmuch as it was moved by the Godhead, as is plain from the synodical letter of Pope Agatho [*Third Council of Constantinople, Act. 4].
And hence in the sixth Council held at Constantinople [*Act. 18] it was decreed that it must be said that there are two wills in Christ, in the following passage: "In accordance with what the Prophets of old taught us concerning Christ, and as He taught us Himself, and the Symbol of the Holy Fathers has handed down to us, we confess two natural wills in Him and two natural operations." And this much it was necessary to say. For it is manifest that the Son of God assumed a perfect human nature, as was shown above (Question [5]; Question [9], Article [1]). Now the will pertains to the perfection of human nature, being one of its natural powers, even as the intellect, as was stated in the FP, Questions [79],80. Hence we must say that the Son of God assumed a human will, together with human nature. Now by the assumption of human nature the Son of God suffered no diminution of what pertains to His Divine Nature, to which it belongs to have a will, as was said in the FP, Question [19], Article [1]. Hence it must be said that there are two wills in Christ, i.e. one human, the other Divine.