cling to good." But in the soul, spirit designates a
power--either the mind itself, according to the text (Eph. 4:13), "Be
ye renewed in the spirit of your mind"--or the imagination, whence
imaginary vision is called spiritual, as Augustine says (Gen. ad lit.
xii, 7,24). Therefore conscience is a power.

Obj. 2: Further, nothing is a subject of sin, except a power of the
soul. But conscience is a subject of sin; for it is said of some that
"their mind and conscience are defiled" (Titus 1:15). Therefore it
seems that conscience is a power.

Obj. 3: Further, conscience must of necessity be either an act, a
habit, or a power. But it is not an act; for thus it would not always
exist in man. Nor is it a habit; for conscience is not one thing but
many, since we are directed in our actions by many habits of
knowledge. Therefore conscience is a power.

_On the contrary,_ Conscience can be laid aside. But a power cannot
be laid aside. Therefore conscience is not a power.

_I answer that,_ Properly speaking, conscience is not a power, but an
act. This is evident both from the very name and from those things
which in the common way of speaking are attributed to conscience. For
conscience, according to the very nature of the word, implies the
relation of knowledge to something: for conscience may be resolved
into "cum alio scientia," i.e. knowledge applied to an individual
case. But the application of knowledge to something is done by some
act. Wherefore from this explanation of the name it is clear that
conscience is an act.

The same is manifest from those things which are attributed to
conscience. For conscience is said to witness, to bind, or incite,
and also to accuse, torment, or rebuke. And all these follow the
application of knowledge or science to what we do: which application
is made in three ways. One way in so far as we recognize that we have
done or not done something; "Thy conscience knoweth that thou hast
often spoken evil of others" (Eccles. 7:23), and according to this,
conscience is said to witness. In another way, so far as through the
conscience we judge that something should be done or not done; and in
this sense, conscience is said to incite or to bind. In the third way,
so far as by conscience we judge that something done is well done or
ill done, and in this sense conscience is said to excuse, accuse, or
torment. Now, it is clear that all these things follow the actual
application of knowledge to what