Reply to Objection 2: Truth and good include one another; for truth is something good, otherwise it would not be desirable; and good is something true, otherwise it would not be intelligible. Therefore as the object of the appetite may be something true, as having the aspect of good, for example, when some one desires to know the truth; so the object of the practical intellect is good directed to the operation, and under the aspect of truth. For the practical intellect knows truth, just as the speculative, but it directs the known truth to operation.
Reply to Objection 3: Many differences differentiate the sensitive powers, which do not differentiate the intellectual powers, as we have said above (A[7] , ad 2; Q[77], A[3], ad 4).
Whether synderesis is a special power of the soul distinct from the others?
Objection 1: It would seem that "synderesis" is a special power, distinct from the others. For those things which fall under one division, seem to be of the same genus. But in the gloss of Jerome on Ezech. 1:6, "synderesis" is divided against the irascible, the concupiscible, and the rational, which are powers. Therefore "synderesis" is a power.
Objection 2: Further, opposite things are of the same genus. But "synderesis" and sensuality seem to be opposed to one another because "synderesis" always incites to good; while sensuality always incites to evil: whence it is signified by the serpent, as is clear from Augustine (De Trin. xii, 12,13). It seems, therefore, that 'synderesis' is a power just as sensuality is.
Objection 3: Further, Augustine says (De Lib. Arb. ii, 10) that in the natural power of judgment there are certain "rules and seeds of virtue, both true and unchangeable." And this is what we call synderesis. Since, therefore, the unchangeable rules which guide our judgment belong to the reason as to its higher part, as Augustine says (De Trin. xii, 2), it seems that "synderesis" is the same as reason: and thus it is a power.
On the contrary, According to the Philosopher (Metaph. viii, 2), "rational powers regard opposite things." But "synderesis" does not regard opposites, but inclines to good only. Therefore "synderesis" is not a power. For if it were a power it would be a rational power, since it is not found in brute animals.
I answer 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 to Objection 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 to Objection 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 to Objection 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."
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 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.
Objection 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.
Objection 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 we do. Wherefore, properly speaking, conscience denominates an act. But since habit is a principle of act, sometimes the name conscience is given to the first natural habit---namely, 'synderesis': thus Jerome calls 'synderesis' conscience (Gloss. Ezech. 1:6 ); Basil [*Hom. in princ. Proverb.], the "natural power of judgment," and Damascene [*De Fide Orth. iv. 22] says that it is the "law of our intellect." For it is customary for causes and effects to be called after one another.
Reply to Objection 1: Conscience is called a spirit, so far as spirit is the same as mind; because conscience is a certain pronouncement of the mind.
Reply to Objection 2: The conscience is said to be defiled, not as a subject, but as the thing known is in knowledge; so far as someone knows he is defiled.
Reply to Objection 3: Although an act does not always remain in itself, yet it always remains in its cause, which is power and habit. Now all the habits by which conscience is formed, although many, nevertheless have their efficacy from one first habit, the habit of first principles, which is called "synderesis." And for this special reason, this habit is sometimes called conscience, as we have said above.