Summa Th. I-II EN Qu.55
We come now to the consideration of habits specifically. And since habits, as we have said (Question , Article ), are divided into good and bad, we must speak in the first place of good habits, which are virtues, and of other matters connected with them, namely the Gifts, Beatitudes and Fruits; in the second place, of bad habits, namely of vices and sins. Now five things must be considered about virtues: (1) the essence of virtue; (2) its subject; (3) the division of virtue; (4) the cause of virtue; (5) certain properties of virtue.
Under the first head, there are four points of inquiry:
(1) Whether human virtue is a habit?
(2) Whether it is an operative habit?
(3) Whether it is a good habit?
(4) Of the definition of virtue.
Objection: 1. It would seem that human virtue is not a habit: For virtue is "the limit of power" (De Coelo i, text. 116). But the limit of anything is reducible to the genus of that of which it is the limit; as a point is reducible to the genus of line. Therefore virtue is reducible to the genus of power, and not to the genus of habit.
2. Further, Augustine says (De Lib. Arb. ii) [*Retract. ix; cf. De Lib. Arb. ii, 19] that "virtue is good use of free-will." But use of free-will is an act. Therefore virtue is not a habit, but an act.
3. Further, we do not merit by our habits, but by our actions: otherwise a man would merit continually, even while asleep. But we do merit by our virtues. Therefore virtues are not habits, but acts.
4. Further, Augustine says (De Moribus Eccl. xv) that "virtue is the order of love," and (Questions. lxxxiii, qu. 30) that "the ordering which is called virtue consists in enjoying what we ought to enjoy, and using what we ought to use." Now order, or ordering, denominates either an action or a relation. Therefore virtue is not a habit, but an action or a relation.
5. Further, just as there are human virtues, so are there natural virtues. But natural virtues are not habits, but powers. Neither therefore are human virtues habits.
On the contrary The Philosopher says (Categor. vi) that science and virtue are habits.
I answer that Virtue denotes a certain perfection of a power. Now a thing's perfection is considered chiefly in regard to its end. But the end of power is act. Wherefore power is said to be perfect, according as it is determinate to its act.Now there are some powers which of themselves are determinate to their acts; for instance, the active natural powers. And therefore these natural powers are in themselves called virtues. But the rational powers, which are proper to man, are not determinate to one particular action, but are inclined indifferently to many: and they are determinate to acts by means of habits, as is clear from what we have said above (Question , Article ). Therefore human virtues are habits.
Reply to Objection: 1. Sometimes we give the name of a virtue to that to which the virtue is directed, namely, either to its object, or to its act: for instance, we give the name Faith, to that which we believe, or to the act of believing, as also to the habit by which we believe. When therefore we say that "virtue is the limit of power," virtue is taken for the object of virtue. For the furthest point to which a power can reach, is said to be its virtue; for instance, if a man can carry a hundredweight and not more, his virtue [*In English we should say 'strength,' which is the original signification of the Latin 'virtus': thus we speak of an engine being so many horse-power, to indicate its 'strength'] is put at a hundredweight, and not at sixty. But the objection takes virtue as being essentially the limit of power.
2. Good use of free-will is said to be a virtue, in the same sense as above (ad 1); that is to say, because it is that to which virtue is directed as to its proper act. For the act of virtue is nothing else than the good use of free-will.
3. We are said to merit by something in two ways. First, as by merit itself, just as we are said to run by running; and thus we merit by acts. Secondly, we are said to merit by something as by the principle whereby we merit, as we are said to run by the motive power; and thus are we said to merit by virtues and habits.
4. When we say that virtue is the order or ordering of love, we refer to the end to which virtue is ordered: because in us love is set in order by virtue.
5. Natural powers are of themselves determinate to one act: not so the rational powers. And so there is no comparison, as we have said.
Objection: 1. It would seem that it is not essential to human virtue to be an operative habit. For Tully says (Tuscul. iv) that as health and beauty belong to the body, so virtue belongs to the soul. But health and beauty are not operative habits. Therefore neither is virtue.
2. Further, in natural things we find virtue not only in reference to act, but also in reference to being: as is clear from the Philosopher (De Coelo i), since some have a virtue to be always, while some have a virtue to be not always, but at some definite time. Now as natural virtue is in natural things, so is human virtue in rational beings. Therefore also human virtue is referred not only to act, but also to being.
3. Further, the Philosopher says (Phys. vii, text. 17) that virtue "is the disposition of a perfect thing to that which is best." Now the best thing to which man needs to be disposed by virtue is God Himself, as Augustine proves (De Moribus Eccl. 3,6, 14) to Whom the soul is disposed by being made like to Him. Therefore it seems that virtue is a quality of the soul in reference to God, likening it, as it were, to Him; and not in reference to operation. It is not, therefore, an operative habit.
On the contrary The Philosopher (Ethic. ii, 6) says that "virtue of a thing is that which makes its work good."
I answer that Virtue, from the very nature of the word, implies some perfection of power, as we have said above (Article ). Wherefore, since power [*The one Latin word 'potentia' is rendered 'potentiality' in the first case, and 'power' in the second] is of two kinds, namely, power in reference to being, and power in reference to act; the perfection of each of these is called virtue. But power in reference to being is on the part of matter, which is potential being, whereas power in reference to act, is on the part of the form, which is the principle of action, since everything acts in so far as it is in act.Now man is so constituted that the body holds the place of matter, the soul that of form. The body, indeed, man has in common with other animals; and the same is to be said of the forces which are common to the soul and body: and only those forces which are proper to the soul, namely, the rational forces, belong to man alone. And therefore, human virtue, of which we are speaking now, cannot belong to the body, but belongs only to that which is proper to the soul. Wherefore human virtue does not imply reference to being, but rather to act. Consequently it is essential to human virtue to be an operative habit.
Reply to Objection: 1. Mode of action follows on the disposition of the agent: for such as a thing is, such is its act. And therefore, since virtue is the principle of some kind of operation, there must needs pre-exist in the operator in respect of virtue some corresponding disposition. Now virtue causes an ordered operation. Therefore virtue itself is an ordered disposition of the soul, in so far as, to wit, the powers of the soul are in some way ordered to one another, and to that which is outside. Hence virtue, inasmuch as it is a suitable disposition of the soul, is like health and beauty, which are suitable dispositions of the body. But this does not hinder virtue from being a principle of operation.
2. Virtue which is referred to being is not proper to man; but only that virtue which is referred to works of reason, which are proper to man.
3. As God's substance is His act, the highest likeness of man to God is in respect of some operation. Wherefore, as we have said above (Question , Article ), happiness or bliss by which man is made most perfectly conformed to God, and which is the end of human life, consists in an operation.
Objection: 1. It would seem that it is not essential to virtue that it should be a good habit. For sin is always taken in a bad sense. But there is a virtue even of sin; according to 1Co 15,56: "The virtue [Douay: 'strength'] of sin is the Law." Therefore virtue is not always a good habit.
2. Further, Virtue corresponds to power. But power is not only referred to good, but also to evil: according to Is 5: "Woe to you that are mighty to drink wine, and stout men at drunkenness." Therefore virtue also is referred to good and evil.
3. Further, according to the Apostle (2Co 12,9): "Virtue [Douay: 'power'] is made perfect in infirmity." But infirmity is an evil. Therefore virtue is referred not only to good, but also to evil.
On the contrary Augustine says (De Moribus Eccl. vi): "No one can doubt that virtue makes the soul exceeding good": and the Philosopher says (Ethic. ii, 6): "Virtue is that which makes its possessor good, and his work good likewise."
I answer that As we have said above (Article ), virtue implies a perfection of power: wherefore the virtue of a thing is fixed by the limit of its power (De Coelo i). Now the limit of any power must needs be good: for all evil implies defect; wherefore Dionysius says (Div. Hom. ii) that every evil is a weakness. And for this reason the virtue of a thing must be regarded in reference to good. Therefore human virtue which is an operative habit, is a good habit, productive of good works.
Reply to Objection: 1. Just as bad things are said metaphorically to be perfect, so are they said to be good: for we speak of a perfect thief or robber; and of a good thief or robber, as the Philosopher explains (Metaph. v, text. 21). In this way therefore virtue is applied to evil things: so that the "virtue" of sin is said to be law, in so far as occasionally sin is aggravated through the law, so as to attain to the limit of its possibility.
2. The evil of drunkenness and excessive drink, consists in a falling away from the order of reason. Now it happens that, together with this falling away from reason, some lower power is perfect in reference to that which belongs to its own kind, even in direct opposition to reason, or with some falling away therefrom. But the perfection of that power, since it is compatible with a falling away from reason, cannot be called a human virtue.
3. Reason is shown to be so much the more perfect, according as it is able to overcome or endure more easily the weakness of the body and of the lower powers. And therefore human virtue, which is attributed to reason, is said to be "made perfect in infirmity," not of the reason indeed, but of the body and of the lower powers.
Objection: 1. It would seem that the definition, usually given, of virtue, is not suitable, to wit: "Virtue is a good quality of the mind, by which we live righteously, of which no one can make bad use, which God works in us, without us." For virtue is man's goodness, since virtue it is that makes its subject good. But goodness does not seem to be good, as neither is whiteness white. It is therefore unsuitable to describe virtue as a "good quality."
2. Further, no difference is more common than its genus; since it is that which divides the genus. But good is more common than quality, since it is convertible with being. Therefore "good" should not be put in the definition of virtue, as a difference of quality.
3. Further, as Augustine says (De Trin. xii, 3): "When we come across anything that is not common to us and the beasts of the field, it is something appertaining to the mind." But there are virtues even of the irrational parts; as the Philosopher says (Ethic. iii, 10). Every virtue, therefore, is not a good quality "of the mind."
4. Further, righteousness seems to belong to justice; whence the righteous are called just. But justice is a species of virtue. It is therefore unsuitable to put "righteous" in the definition of virtue, when we say that virtue is that "by which we live righteously."
5. Further, whoever is proud of a thing, makes bad use of it. But many are proud of virtue, for Augustine says in his Rule, that "pride lies in wait for good works in order to slay them." It is untrue, therefore, "that no one can make bad use of virtue."
6. Further, man is justified by virtue. But Augustine commenting on Jn 14,12: "He shall do greater things than these," says [*Tract. xxvii in Joan.: Serm. xv de Verb. Ap. 11]: "He who created thee without thee, will not justify thee without thee." It is therefore unsuitable to say that "God works virtue in us, without us."
On the contrary We have the authority of Augustine from whose words this definition is gathered, and principally in De Libero Arbitrio ii, 19.
I answer that This definition comprises perfectly the whole essential notion of virtue. For the perfect essential notion of anything is gathered from all its causes. Now the above definition comprises all the causes of virtue. For the formal cause of virtue, as of everything, is gathered from its genus and difference, when it is defined as "a good quality": for "quality" is the genus of virtue, and the difference, "good." But the definition would be more suitable if for "quality" we substitute "habit," which is the proximate genus.Now virtue has no matter "out of which" it is formed, as neither has any other accident; but it has matter "about which" it is concerned, and matter "in which" it exits, namely, the subject. The matter about which virtue is concerned is its object, and this could not be included in the above definition, because the object fixes the virtue to a certain species, and here we are giving the definition of virtue in general. And so for material cause we have the subject, which is mentioned when we say that virtue is a good quality "of the mind."The end of virtue, since it is an operative habit, is operation. But it must be observed that some operative habits are always referred to evil, as vicious habits: others are sometimes referred to good, sometimes to evil; for instance, opinion is referred both to the true and to the untrue: whereas virtue is a habit which is always referred to good: and so the distinction of virtue from those habits which are always referred to evil, is expressed in the words "by which we live righteously": and its distinction from those habits which are sometimes directed unto good, sometimes unto evil, in the words, "of which no one makes bad use."Lastly, God is the efficient cause of infused virtue, to which this definition applies; and this is expressed in the words "which God works in us without us." If we omit this phrase, the remainder of the definition will apply to all virtues in general, whether acquired or infused.
Reply to Objection: 1. That which is first seized by the intellect is being: wherefore everything that we apprehend we consider as being, and consequently as gone, and as good, which are convertible with being. Wherefore we say that essence is being and is one and is good; and that oneness is being and one and good: and in like manner goodness. But this is not the case with specific forms, as whiteness and health; for everything that we apprehend, is not apprehended with the notion of white and healthy. We must, however, observe that, as accidents and non-subsistent forms are called beings, not as if they themselves had being, but because things are by them; so also are they called good or one, not by some distinct goodness or oneness, but because by them something is good or one. So also is virtue called good, because by it something is good.
2. Good, which is put in the definition of virtue, is not good in general which is convertible with being, and which extends further than quality, but the good as fixed by reason, with regard to which Dionysius says (Div. Nom. iv) "that the good of the soul is to be in accord with reason."
3. Virtue cannot be in the irrational part of the soul, except in so far as this participates in the reason (Ethic. i, 13). And therefore reason, or the mind, is the proper subject of virtue.
4. Justice has a righteousness of its own by which it puts those outward things right which come into human use, and are the proper matter of justice, as we shall show further on (Question , Article ; II-II 58,8). But the righteousness which denotes order to a due end and to the Divine law, which is the rule of the human will, as stated above (Question , Article ), is common to all virtues.
5. One can make bad use of a virtue objectively, for instance by having evil thoughts about a virtue, e.g. by hating it, or by being proud of it: but one cannot make bad use of virtue as principle of action, so that an act of virtue be evil.
6. Infused virtue is caused in us by God without any action on our part, but not without our consent. This is the sense of the words, "which God works in us without us." As to those things which are done by us, God causes them in us, yet not without action on our part, for He works in every will and in every nature.
We now have to consider the subject of virtue, about which there are six points of inquiry:
(1) Whether the subject of virtue is a power of the soul?
(2) Whether one virtue can be in several powers?
(3) Whether the intellect can be the subject of virtue?
(4) Whether the irascible and concupiscible faculties can be the subject of virtue?
(5) Whether the sensitive powers of apprehension can be the subject of virtue?
(6) Whether the will can be the subject of virtue?
Objection: 1. It would seem that the subject of virtue is not a power of the soul. For Augustine says (De Lib. Arb. ii, 19) that "virtue is that by which we live righteously." But we live by the essence of the soul, and not by a power of the soul. Therefore virtue is not a power, but in the essence of the soul.
2. Further, the Philosopher says (Ethic. ii, 6) that "virtue is that which makes its possessor good, and his work good likewise." But as work is set up by power, so he that has a virtue is set up by the essence of the soul. Therefore virtue does not belong to the power, any more than to the essence of the soul.
3. Further, power is in the second species of quality. But virtue is a quality, as we have said above (Question , Article ): and quality is not the subject of quality. Therefore a power of the soul is not the subject of virtue.
On the contrary "Virtue is the limit of power" (De Coelo ii). But the limit is in that of which it is the limit. Therefore virtue is in a power of the soul.
I answer that It can be proved in three ways that virtue belongs to a power of the soul. First, from the notion of the very essence of virtue, which implies perfection of a power; for perfection is in that which it perfects. Secondly, from the fact that virtue is an operative habit, as we have said above (Question , Article ): for all operation proceeds from the soul through a power. Thirdly, from the fact that virtue disposes to that which is best: for the best is the end, which is either a thing's operation, or something acquired by an operation proceeding from the thing's power. Therefore a power of the soul is the subject of virtue.
Reply to Objection: 1. "To live" may be taken in two ways. Sometimes it is taken for the very existence of the living thing: in this way it belongs to the essence of the soul, which is the principle of existence in the living thing. But sometimes "to live" is taken for the operation of the living thing: in this sense, by virtue we live righteously, inasmuch as by virtue we perform righteous actions.
2. Good is either the end, or something referred to the end. And therefore, since the good of the worker consists in the work, this fact also, that virtue makes the worker good, is referred to the work, and consequently, to the power.
3. One accident is said to be the subject of another, not as though one accident could uphold another; but because one accident inheres to substance by means of another, as color to the body by means of the surface; so that surface is said to be the subject of color. In this way a power of the soul is said to be the subject of virtue.
Objection: 1. It would seem that one virtue can be in several powers. For habits are known by their acts. But one act proceeds in various way from several powers: thus walking proceeds from the reason as directing, from the will as moving, and from the motive power as executing. Therefore also one habit can be in several powers.
2. Further, the Philosopher says (Ethic. ii, 4) that three things are required for virtue, namely: "to know, to will, and to work steadfastly." But "to know" belongs to the intellect, and "to will" belongs to the will. Therefore virtue can be in several powers.
3. Further, prudence is in the reason since it is "the right reason of things to be done" (Ethic. vi, 5). And it is also in the will: for it cannot exist together with a perverse will (Ethic. vi, 12). Therefore one virtue can be in two powers.
On the contrary The subject of virtue is a power of the soul. But the same accident cannot be in several subjects. Therefore one virtue cannot be in several powers of the soul.
I answer that It happens in two ways that one thing is subjected in two. First, so that it is in both on an equal footing. In this way it is impossible for one virtue to be in two powers: since diversity of powers follows the generic conditions of the objects, while diversity of habits follows the specific conditions thereof: and so wherever there is diversity of powers, there is diversity of habits; but not vice versa. In another way one thing can be subjected in two or more, not on an equal footing, but in a certain order. And thus one virtue can belong to several powers, so that it is in one chiefly, while it extends to others by a kind of diffusion, or by way of a disposition, in so far as one power is moved by another, and one power receives from another.
Reply to Objection: 1. One act cannot belong to several powers equally, and in the same degree; but only from different points of view, and in various degrees.
2. "To know" is a condition required for moral virtue, inasmuch as moral virtue works according to right reason. But moral virtue is essentially in the appetite.
3. Prudence is really subjected in reason: but it presupposes as its principle the rectitude of the will, as we shall see further on (Article ; Question , Article ).
Objection: 1. It would seem that the intellect is not the subject of virtue. For Augustine says (De Moribus Eccl. xv) that all virtue is love. But the subject of love is not the intellect, but the appetitive power alone. Therefore no virtue is in the intellect.
2. Further, virtue is referred to good, as is clear from what has been said above (Question , Article ). Now good is not the object of the intellect, but of the appetitive power. Therefore the subject of virtue is not the intellect, but the appetitive power.
3. Further, virtue is that "which makes its possessor good," as the Philosopher says (Ethic. ii, 6). But the habit which perfects the intellect does not make its possessor good: since a man is not said to be a good man on account of his science or his art. Therefore the intellect is not the subject of virtue.
On the contrary The mind is chiefly called the intellect. But the subject of virtue is the mind, as is clear from the definition, above given, of virtue (Question , Article ). Therefore the intellect is the subject of virtue.
I answer that As we have said above (Question , Article ), a virtue is a habit by which we work well. Now a habit may be directed to a good act in two ways. First, in so far as by the habit a man acquires an aptness to a good act; for instance, by the habit of grammar man has the aptness to speak correctly. But grammar does not make a man always speak correctly: for a grammarian may be guilty of a barbarism or make a solecism: and the case is the same with other sciences and arts. Secondly, a habit may confer not only aptness to act, but also the right use of that aptness: for instance, justice not only gives man the prompt will to do just actions, but also makes him act justly.And since good, and, in like manner, being, is said of a thing simply, in respect, not of what it is potentially, but of what it is actually: therefore from having habits of the latter sort, man is said simply to do good, and to be good; for instance, because he is just, or temperate; and in like manner as regards other such virtues. And since virtue is that "which makes its possessor good, and his work good likewise," these latter habits are called virtuous simply: because they make the work to be actually good, and the subject good simply. But the first kind of habits are not called virtues simply: because they do not make the work good except in regard to a certain aptness, nor do they make their possessor good simply. For through being gifted in science or art, a man is said to be good, not simply, but relatively; for instance, a good grammarian or a good smith. And for this reason science and art are often divided against virtue; while at other times they are called virtues (Ethic. vi, 2).Hence the subject of a habit which is called a virtue in a relative sense, can be the intellect, and not only the practical intellect, but also the speculative, without any reference to the will: for thus the Philosopher (Ethic. vi, 3) holds that science, wisdom and understanding, and also art, are intellectual virtues. But the subject of a habit which is called a virtue simply, can only be the will, or some power in so far as it is moved by the will. And the reason of this is, that the will moves to their acts all those other powers that are in some way rational, as we have said above (Question , Article ; Question , Articles ,5; I 82,4): and therefore if man do well actually, this is because he has a good will. Therefore the virtue which makes a man to do well actually, and not merely to have the aptness to do well, must be either in the will itself; or in some power as moved by the will.Now it happens that the intellect is moved by the will, just as are the other powers: for a man considers something actually, because he wills to do so. And therefore the intellect, in so far as it is subordinate to the will, can be the subject of virtue absolutely so called. And in this way the speculative intellect, or the reason, is the subject of Faith: for the intellect is moved by the command of the will to assent to what is of faith: for "no man believeth, unless he will" [*Augustine: Tract. xxvi in Joan.]. But the practical intellect is the subject of prudence. For since prudence is the right reason of things to be done, it is a condition thereof that man be rightly disposed in regard to the principles of this reason of things to be done, that is in regard to their ends, to which man is rightly disposed by the rectitude of the will, just as to the principles of speculative truth he is rightly disposed by the natural light of the active intellect. And therefore as the subject of science, which is the right reason of speculative truths, is the speculative intellect in its relation to the active intellect, so the subject of prudence is the practical intellect in its relation to the right will.
Reply to Objection: 1. The saying of Augustine is to be understood of virtue simply so called: not that every virtue is love simply: but that it depends in some way on love, in so far as it depends on the will, whose first movement consists in love, as we have said above (Question , Articles ,2,3; Question , Article ; I 20,1).
2. The good of each thing is its end: and therefore, as truth is the end of the intellect, so to know truth is the good act of the intellect. Whence the habit, which perfects the intellect in regard to the knowledge of truth, whether speculative or practical, is a virtue.
3. This objection considers virtue simply so called.
Objection: 1. It would seem that the irascible and concupiscible powers cannot be the subject of virtue. For these powers are common to us and dumb animals. But we are now speaking of virtue as proper to man, since for this reason it is called human virtue. It is therefore impossible for human virtue to be in the irascible and concupiscible powers which are parts of the sensitive appetite, as we have said in the I 81,2.
2. Further, the sensitive appetite is a power which makes use of a corporeal organ. But the good of virtue cannot be in man's body: for the Apostle says (Rm 7): "I know that good does not dwell in my flesh." Therefore the sensitive appetite cannot be the subject of virtue.
3. Further, Augustine proves (De Moribus Eccl. v) that virtue is not in the body but in the soul, for the reason that the body is ruled by the soul: wherefore it is entirely due to his soul that a man make good use of his body: "For instance, if my coachman, through obedience to my orders, guides well the horses which he is driving; this is all due to me." But just as the soul rules the body, so also does the reason rule the sensitive appetite. Therefore that the irascible and concupiscible powers are rightly ruled, is entirely due to the rational powers. Now "virtue is that by which we live rightly," as we have said above (Question , Article ). Therefore virtue is not in the irascible and concupiscible powers, but only in the rational powers.
4. Further, "the principal act of moral virtue is choice" (Ethic. viii, 13). Now choice is not an act of the irascible and concupiscible powers, but of the rational power, as we have said above (Question , Article ). Therefore moral virtue is not in the irascible and concupiscible powers, but in the reason.
On the contrary Fortitude is assigned to the irascible power, and temperance to the concupiscible power. Whence the Philosopher (Ethic. iii, 10) says that "these virtues belong to the irrational part of the soul."
I answer that The irascible and concupiscible powers can be considered in two ways. First, in themselves, in so far as they are parts of the sensitive appetite: and in this way they are not competent to be the subject of virtue. Secondly, they can be considered as participating in the reason, from the fact that they have a natural aptitude to obey reason. And thus the irascible or concupiscible power can be the subject of human virtue: for, in so far as it participates in the reason, it is the principle of a human act. And to these powers we must needs assign virtues.For it is clear that there are some virtues in the irascible and concupiscible powers. Because an act, which proceeds from one power according as it is moved by another power, cannot be perfect, unless both powers be well disposed to the act: for instance, the act of a craftsman cannot be successful unless both the craftsman and his instrument be well disposed to act. Therefore in the matter of the operations of the irascible and concupiscible powers, according as they are moved by reason, there must needs be some habit perfecting in respect of acting well, not only the reason, but also the irascible and concupiscible powers. And since the good disposition of the power which moves through being moved, depends on its conformity with the power that moves it: therefore the virtue which is in the irascible and concupiscible powers is nothing else but a certain habitual conformity of these powers to reason.
Reply to Objection: 1. The irascible and concupiscible powers considered in themselves, as parts of the sensitive appetite, are common to us and dumb animals. But in so far as they are rational by participation, and are obedient to the reason, they are proper to man. And in this way they can be the subject of human virtue.
2. Just as human flesh has not of itself the good of virtue, but is made the instrument of a virtuous act, inasmuch as being moved by reason, we "yield our members to serve justice"; so also, the irascible and concupiscible powers, of themselves indeed, have not the good of virtue, but rather the infection of the "fomes": whereas, inasmuch as they are in conformity with reason, the good of reason is begotten in them.
3. The body is ruled by the soul, and the irascible and concupiscible powers by the reason, but in different ways. For the body obeys the soul blindly without any contradiction, in those things in which it has a natural aptitude to be moved by the soul: whence the Philosopher says (Polit. i, 3) that the "soul rules the body with a despotic command" as the master rules his slave: wherefore the entire movement of the body is referred to the soul. For this reason virtue is not in the body, but in the soul. But the irascible and concupiscible powers do not obey the reason blindly; on the contrary, they have their own proper movements, by which, at times, they go against reason, whence the Philosopher says (Polit. i, 3) that the "reason rules the irascible and concupiscible powers by a political command" such as that by which free men are ruled, who have in some respects a will of their own. And for this reason also must there be some virtues in the irascible and concupiscible powers, by which these powers are well disposed to act.
4. In choice there are two things, namely, the intention of the end, and this belongs to the moral virtue; and the preferential choice of that which is unto the end, and this belongs to prudence (Ethic. vi, 2,5). But that the irascible and concupiscible powers have a right intention of the end in regard to the passions of the soul, is due to the good disposition of these powers. And therefore those moral virtues which are concerned with the passions are in the irascible and concupiscible powers, but prudence is in the reason.
Summa Th. I-II EN Qu.55