Whether the speculative and practical intellects are distinct powers?
Objection 1: It would seem that the speculative and practical intellects are distinct powers. For the apprehensive and motive are different kinds of powers, as is clear from De Anima ii, 3. But the speculative intellect is merely an apprehensive power; while the practical intellect is a motive power. Therefore they are distinct powers.
Objection 2: Further, the different nature of the object differentiates the power. But the object of the speculative intellect is "truth," and of the practical is "good"; which differ in nature. Therefore the speculative and practical intellect are distinct powers.
Objection 3: Further, in the intellectual part, the practical intellect is compared to the speculative, as the estimative is to the imaginative power in the sensitive part. But the estimative differs from the imaginative, as power form power, as we have said above (Q 78, A 4). Therefore also the speculative intellect differs from the practical.
On the contrary, The speculative intellect by extension becomes practical (De Anima iii, 10). But one power is not changed into another. Therefore the speculative and practical intellects are not distinct powers.
I answer that, The speculative and practical intellects are not distinct powers. The reason of which is that, as we have said above (Q 77, A 3), what is accidental to the nature of the object of a power, does not differentiate that power; for it is accidental to a thing colored to be man, or to be great or small; hence all such things are apprehended by the same power of sight. Now, to a thing apprehended by the intellect, it is accidental whether it be directed to operation or not, and according to this the speculative and practical intellects differ. For it is the speculative intellect which directs what it apprehends, not to operation, but to the consideration of truth; while the practical intellect is that which directs what it apprehends to operation. And this is what the Philosopher says (De Anima iii, 10); that "the speculative differs from the practical in its end." Whence each is named from its end: the one speculative, the other practical---i.e. operative.
Reply to Objection 1: The practical intellect is a motive power, not as executing movement, but as directing towards it; and this belongs to it according to its mode of apprehension.
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).
I · Q. 79, Art. 12: Whether synderesis is a special power of the soul distinct from the others?
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 "synderesis" 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."