Reply Obj. 1: As we have said above (Q. 81, A. 3, ad 2), the sensitive appetite, though it obeys the reason, yet in a given case can resist by desiring what the reason forbids. This is therefore the good which man does not when he wishes—namely, "not to desire against reason," as Augustine says.
Reply Obj. 2: Those words of the Apostle are not to be taken as though man does not wish or does not run of his free-will, but because the free-will is not sufficient thereto unless it be moved and helped by God.
Reply Obj. 3: Free-will is the cause of its own movement, because by his free-will man moves himself to act. But it does not of necessity belong to liberty that what is free should be the first cause of itself, as neither for one thing to be cause of another need it be the first cause. God, therefore, is the first cause, Who moves causes both natural and voluntary. And just as by moving natural causes He does not prevent their acts being natural, so by moving voluntary causes He does not deprive their actions of being voluntary: but rather is He the cause of this very thing in them; for He operates in each thing according to its own nature.
Reply Obj. 4: "Man's way" is said "not to be his" in the execution of his choice, wherein he may be impeded, whether he will or not. The choice itself, however, is in us, but presupposes the help of God.
Reply Obj. 5: Quality in man is of two kinds: natural and adventitious. Now the natural quality may be in the intellectual part, or in the body and its powers. From the very fact, therefore, that man is such by virtue of a natural quality which is in the intellectual part, he naturally desires his last end, which is happiness. Which desire, indeed, is a natural desire, and is not subject to free-will, as is clear from what we have said above (Q. 82, AA. 1, 2). But on the part of the body and its powers man may be such by virtue of a natural quality, inasmuch as he is of such a temperament or disposition due to any impression whatever produced by corporeal causes, which cannot affect the intellectual part, since it is not the act of a corporeal organ. And such as a man is by virtue of a corporeal quality, such also does his end seem to him, because from such a disposition a man is inclined to choose or reject something. But these inclinations are subject to the judgment of reason, which the lower appetite obeys, as we have said (Q. 81, A. 3). Wherefore this is in no way prejudicial to free-will.
The adventitious qualities are habits and passions, by virtue of which a man is inclined to one thing rather than to another. And yet even these inclinations are subject to the judgment of reason. Such qualities, too, are subject to reason, as it is in our power either to acquire them, whether by causing them or disposing ourselves to them, or to reject them. And so there is nothing in this that is repugnant to free-will. _______________________
SECOND ARTICLE [I, Q. 83, Art. 2]
Whether Free-Will Is a Power?
Objection 1: It would seem that free-will is not a power. For free-will is nothing but a free judgment. But judgment denominates an act, not a power. Therefore free-will is not a power.
Obj. 2: Further, free-will is defined as "the faculty of the will and reason." But faculty denominates a facility of power, which is due to a habit. Therefore free-will is a habit. Moreover Bernard says (De Gratia et Lib. Arb. 1,2) that free-will is "the soul's habit of disposing of itself." Therefore it is not a power.