Whether the will alone is the subject of sin?

Objections

Objection 1 : It would seem that the will alone is the subject of sin. For Augustine says (De Duabus Anim. x, 10) that "no one sins except by the will." Now the subject of sin is the power by which we sin. Therefore the will alone is the subject of sin.
Objection 2 : Further, sin is an evil contrary to reason. Now good and evil pertaining to reason are the object of the will alone. Therefore the will alone is the subject of sin.
Objection 3 : Further, every sin is a voluntary act, because, as Augustine states (De Lib. Arb. iii, 18) [*Cf. De Vera Relig. xiv.], "so true is it that every sin is voluntary, that unless it be voluntary, it is no sin at all." Now the acts of the other powers are not voluntary, except in so far as those powers are moved by the will; nor does this suffice for them to be the subject of sin, because then even the external members of the body, which are moved by the will, would be a subject of sin; which is clearly untrue. Therefore the will alone is the subject of sin.