are all moral acts, whether virtuous or sinful.  Consequently the proper subject of sin must needs be the power which is the principle of the act.  Now since it is proper to moral acts that they are voluntary, as stated above (Q. 1, A. 1; Q. 18, A. 6), it follows that the will, which is the principle of voluntary acts, both of good acts, and of evil acts or sins, is the principle of sins.  Therefore it follows that sin is in the will as its subject.

Reply Obj. 1:  Evil is said to be outside the will, because the will does not tend to it under the aspect of evil.  But since some evil is an apparent good, the will sometimes desires an evil, and in this sense is in the will.

Reply Obj. 2:  If the defect in the apprehensive power were nowise subject to the will, there would be no sin, either in the will, or in the apprehensive power, as in the case of those whose ignorance is invincible.  It remains therefore that when there is in the apprehensive power a defect that is subject to the will, this defect also is deemed a sin.

Reply Obj. 3:  This argument applies to those efficient causes whose actions pass into external matter, and which do not move themselves, but move other things; the contrary of which is to be observed in the will; hence the argument does not prove. ________________________

SECOND ARTICLE [I-II, Q. 74, Art. 2]

Whether the Will Alone Is the Subject of Sin?

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.

Obj. 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.

Obj. 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.

On the contrary, Sin is contrary to virtue:  and contraries are about one same thing.  But the other powers of the soul, besides the will, are the subject of virtues, as stated above (Q. 56).  Therefore the will is not the only subject of sin.

I answer that, As was shown above (A. 1), whatever is the a principle of a voluntary act is a subject of sin.  Now voluntary acts are not only those which are elicited by the will, but also those which are commanded by the will, as we stated above (Q. 6, A. 4) in treating of voluntariness.  Therefore not only the will can be a subject of sin, but also all those powers which can be moved to their acts, or restrained from their acts, by the will; and these same powers are the subjects of good and evil moral habits, because act and habit belong to the same subject.