iii, 18). But man cannot prevent the movement of
the sensuality from being inordinate, since "the sensuality ever
remains corrupt, so long as we abide in this mortal life; wherefore
it is signified by the serpent," as Augustine declares (De Trin. xii,
12, 13). Therefore the inordinate movement of the sensuality is not a
sin.

Obj. 3: Further, that which man himself does not do is not imputed to
him as a sin. Now "that alone do we seem to do ourselves, which we do
with the deliberation of reason," as the Philosopher says (Ethic. ix,
8). Therefore the movement of the sensuality, which is without the
deliberation of reason, is not imputed to a man as a sin.

_On the contrary,_ It is written (Rom. 7:19): "The good which I will
I do not; but the evil which I will not, that I do": which words
Augustine explains (Contra Julian. iii, 26; De Verb. Apost. xii, 2,
3), as referring to the evil of concupiscence, which is clearly a
movement of the sensuality. Therefore there can be sin in the
sensuality.

_I answer that,_ As stated above (AA. 2, 3), sin may be found in any
power whose act can be voluntary and inordinate, wherein consists the
nature of sin. Now it is evident that the act of the sensuality, or
sensitive appetite, is naturally inclined to be moved by the will.
Wherefore it follows that sin can be in the sensuality.

Reply Obj. 1: Although some of the powers of the sensitive part are
common to us and irrational animals, nevertheless, in us, they have a
certain excellence through being united to the reason; thus we
surpass other animals in the sensitive part for as much as we have
the powers of cogitation and reminiscence, as stated in the First
Part (Q. 78, A. 4). In the same way our sensitive appetite surpasses
that of other animals by reason of a certain excellence consisting in
its natural aptitude to obey the reason; and in this respect it can
be the principle of a voluntary action, and, consequently, the
subject of sin.

Reply Obj. 2: The continual corruption of the sensuality is to be
understood as referring to the _fomes,_ which is never completely
destroyed in this life, since, though the stain of original sin
passes, its effect remains. However, this corruption of the _fomes_
does not hinder man from using his rational will to check individual
inordinate movements, if he be presentient of them, for instance by
turning his thoughts to other things. Yet while he is turning his
thoughts to something else, an