wer that,_ "Synderesis" is not a power but a habit; though
some held that it is a power higher than reason; while others [*Cf.
Alexander of Hales, Sum. Theol. II, Q. 73] said that it is reason
itself, not as reason, but as a nature. In order to make this clear
we must observe that, as we have said above (A. 8), man's act of
reasoning, since it is a kind of movement, proceeds from the
understanding of certain things--namely, those which are naturally
known without any investigation on the part of reason, as from an
immovable principle--and ends also at the understanding, inasmuch as
by means of those principles naturally known, we judge of those things
which we have discovered by reasoning. Now it is clear that, as the
speculative reason argues about speculative things, so that practical
reason argues about practical things. Therefore we must have, bestowed
on us by nature, not only speculative principles, but also practical
principles. Now the first speculative principles bestowed on us by
nature do not belong to a special power, but to a special habit, which
is called "the understanding of principles," as the Philosopher
explains (Ethic. vi, 6). Wherefore the first practical principles,
bestowed on us by nature, do not belong to a special power, but to a
special natural habit, which we call "synderesis." Whence "synderesis"
is said to incite to good, and to murmur at evil, inasmuch as through
first principles we proceed to discover, and judge of what we have
discovered. It is therefore clear that "synderesis" is not a power,
but a natural habit.

Reply Obj. 1: The division given by Jerome is taken from the variety
of acts, and not from the variety of powers; and various acts can
belong to one power.

Reply Obj. 2: In like manner, the opposition of sensuality to
"syneresis" is an opposition of acts, and not of the different
species of one genus.

Reply Obj. 3: Those unchangeable notions are the first practical
principles, concerning which no one errs; and they are attributed to
reason as to a power, and to "synderesis" as to a habit. Wherefore
we judge naturally both by our reason and by "synderesis."
_______________________

THIRTEENTH ARTICLE [I, Q. 79, Art. 13]

Whether Conscience Be a Power?

Objection 1: It would seem that conscience is a power; for Origen
says [*Commentary on Rom. 2:15] that "conscience is a correcting and
guiding spirit accompanying the soul, by which it is led away from
evil and made to