cannot be more or less. Therefore a habit cannot increase.
Obj. 3: Further, those things which can be more or less are subject to alteration: for that which from being less hot becomes more hot, is said to be altered. But in habits there is no alteration, as is proved in _Phys._ vii, text. 15, 17. Therefore habits cannot increase.
_On the contrary,_ Faith is a habit, and yet it increases: wherefore the disciples said to our Lord (Luke 17:5): "Lord, increase our faith." Therefore habits increase.
_I answer that,_ Increase, like other things pertaining to quantity, is transferred from bodily quantities to intelligible spiritual things, on account of the natural connection of the intellect with corporeal things, which come under the imagination. Now in corporeal quantities, a thing is said to be great, according as it reaches the perfection of quantity due to it; wherefore a certain quantity is reputed great in man, which is not reputed great in an elephant. And so also in forms, we say a thing is great because it is perfect. And since good has the nature of perfection, therefore "in things which are great, but not in quantity, to be greater is the same as to be better," as Augustine says (De Trin. vi, 8).
Now the perfection of a form may be considered in two ways: first, in respect of the form itself: secondly, in respect of the participation of the form by its subject. In so far as we consider the perfections of a form in respect of the form itself, thus the form is said to be "little" or "great": for instance great or little health or science.
But in so far as we consider the perfection of a form in respect of the participation thereof by the subject, it is said to be "more" or "less": for instance more or less white or healthy. Now this distinction is not to be understood as implying that the form has a being outside its matter or subject, but that it is one thing to consider the form according to its specific nature, and another to consider it in respect of its participation by a subject.
In this way, then, there were four opinions among philosophers concerning intensity and remission of habits and forms, as Simplicius relates in his _Commentary on the Predicaments._ For Plotinus and the other Platonists held that qualities and habits themselves were susceptible of more or less, for the reason that they were material and so had a certain want of definiteness, on account of the infinity of matter. Others, on the contrary, held that qualities and habits of themselves were not susceptible of more or less; but that the things affected by them (_qualia_) are said to be more or less, in respect of the participation of the subject: that, for instance, justice is not more or less, but the just thing. Aristotle alludes to this opinion in the _Predicaments_ (Categor. vi). The third opinion was that of the Stoics, and lies between the two preceding opinions. For they held that some habits are of themselves susceptible of more and less, for instance, the arts; and that some are not, as the virtues.
The fourth opinion was held by some who said that qualities and immaterial forms are not susceptible of more or less, but that material forms are.
In order that the truth in this matter be made clear, we must observe that [that], in respect of which a thing receives its species, must be something fixed and stationary, and as it were indivisible: for whatever attains to that thing, is contained under the species, and whatever recedes from it more or less, belongs to another species, more or less perfect. Wherefore, the Philosopher says (Metaph. viii, text. 10) that species of things are like numbers, in which addition or subtraction changes the species. If, therefore, a form, or anything at all, receives its specific nature in respect of itself, or in respect of something belonging to it, it is necessary that, considered in itself, it be something of a definite nature, which can be neither more nor less. Such are heat, whiteness or other like qualities which are not denominated from a relation to something else: and much more so, substance, which is _per se_ being. But those things which receive their species from something to which they are related, can be diversified, in respect of themselves, according to more or less: and nonetheless they remain in the same species, on account of the oneness of that to which they are related, and from which they receive their species. For example, movement is in itself more intense or more remiss: and yet it remains in the same species, on account of the oneness of the term by which it is specified. We may observe the same thing in health; for a body attains to the nature of health, according as it has a disposition suitable to an animal's nature, to which various dispositions may be suitable; which disposition is therefore variable as regards more or less, and withal the nature of health remains. Whence the Philosopher says (Ethic. x, 2, 3): "Health itself may be more or less: for the measure is not the same in all, nor is it always the same in one individual; but down to a certain point it may decrease and still remain health."
Now these various dispositions and measures of health are by way of excess and defect: wherefore if the name of health were given to the most perfect measure, then we should not speak of health as greater or less. Thus therefore it is clear how a quality or form may increase or decrease of itself, and how it cannot.
But if we consider a quality or form in respect of its participation by the subject, thus again we find that some qualities and forms are susceptible of more or less, and some not. Now Simplicius assigns the cause of this diversity to the fact that substance in itself cannot be susceptible of more or less, because it is _per se_ being. And therefore every form which is participated substantially by its subject, cannot vary in intensity and remission: wherefore in the genus of substance nothing is said to be more or less. And because quantity is nigh to substance, and because shape follows on quantity, therefore is it that neither in these can there be such a thing as more or less. Whence the Philosopher says (Phys. vii, text. 15) that when a thing receives form and shape, it is not said to be altered, but to be made. But other qualities which are further removed from quantity, and are connected with passions and actions, are susceptible of more or less, in respect of their participation by the subject.
Now it is possible to explain yet further the reason of this diversity. For, as we have said, that from which a thing receives its species must remain indivisibly fixed and constant in something indivisible. Wherefore in two ways it may happen that a form cannot be participated more or less. First because the participator has its species in respect of that form. And for this reason no substantial form is participated more or less. Wherefore the Philosopher says (Metaph. viii, text. 10) that, "as a number cannot be more or less, so neither can that which is in the species of substance," that is, in respect of its participation of the specific form: "but in so far as substance may be with matter," i.e. in respect of material dispositions, "more or less are found in substance."
Secondly this may happen from the fact that the form is essentially indivisible: wherefore if anything participate that form, it must needs participate it in respect of its indivisibility. For this reason we do not speak of the species of number as varying in respect of more or less; because each species thereof is constituted by an indivisible unity. The same is to be said of the species of continuous quantity, which are denominated from numbers, as two-cubits-long, three-cubits-long, and of relations of quantity, as double and treble, and of figures of quantity, as triangle and tetragon.
This same explanation is given by Aristotle in the _Predicaments_ (Categor. vi), where in explaining why figures are not susceptible of more or less, he says: "Things which are given the nature of a triangle or a circle, are accordingly triangles and circles": to wit, because indivisibility is essential to the motion of such, wherefore whatever participates their nature must participate it in its indivisibility.
It is clear, therefore, since we speak of habits and dispositions in respect of a relation to something (Phys. vii, text. 17), that in two ways intensity and remission may be observed in habits and dispositions. First, in respect of the habit itself: thus, for instance, we speak of greater or less health; greater or less science, which extends to more or fewer things. Secondly, in respect of participation by the subject: in so far as equal science or health is participated more in one than in another, according to a diverse aptitude arising either from nature, or from custom. For habit and disposition do not give species to the subject: nor again do they essentially imply indivisibility.
We shall say further on (Q. 66, A. 1) how it is with the virtues.
Reply Obj. 1: As the word "great" is taken from corporeal quantities and applied to the intelligible perfections of forms; so also is the word "growth," the term of which is something great.
Reply Obj. 2: Habit is indeed a perfection, but not a perfection which is the term of its subject; for instance, a term giving the subject its specific being. Nor again does the nature of a habit include the notion of term, as do the species of numbers. Wherefore there is nothing to hinder it from being susceptible of more or less.
Reply Obj. 3: Alteration is primarily indeed in the qualities of the third species; but secondarily it may be in the qualities of the first species: for, supposing an alteration as to hot and cold, there follows in an animal an alteration as to health and sickness. In like manner, if an alteration take place in the passions of the sensitive appetite, or the sensitive powers of apprehension, an alteration follows as to science and virtue (Phys. viii, text. 20).
Whether Habit Increases by Addition?
Objection 1: It would seem that the increase of habits is by way of addition. For the word "increase," as we have said, is transferred to forms, from corporeal quantities. But in corporeal quantities there is no increase without addition: wherefore (De Gener. i, text. 31) it is said that "increase is an addition to a magnitude already existing." Therefore in habits also there is no increase without addition.
Obj. 2: Further, habit is not increased except by means of some agent. But every agent does something in the passive subject: for instance, that which heats, causes heat in that which is heated.
Therefore there is no increase without addition.
Obj. 3: Further, as that which is not white, is in potentiality to be white: so that which is less white, is in potentiality to be more white. But that which is not white, is not made white except by the addition of whiteness. Therefore that which is less white, is not made more white, except by an added whiteness.
_On the contrary,_ The Philosopher says (Phys. iv, text. 84): "That which is hot is made hotter, without making, in the matter, something hot, that was not hot, when the thing was less hot." Therefore, in like manner, neither is any addition made in other forms when they increase.
_I answer that,_ The solution of this question depends on what we have said above (A. 1). For we said that increase and decrease in forms which are capable of intensity and remissness, happen in one way not on the part of the very form considered in itself, through the diverse participation thereof by the subject. Wherefore such increase of habits and other forms, is not caused by an addition of form to form; but by the subject participating more or less perfectly, one and the same form. And just as, by an agent which is in act, something is made actually hot, beginning, as it were, to participate a form, not as though the form itself were made, as is proved in _Metaph._ vii, text. 32, so, by an intense action of the agent, something is made more hot, as it were participating the form more perfectly, not as though something were added to the form.
For if this increase in forms were understood to be by way of addition, this could only be either in the form itself or in the subject. If it be understood of the form itself, it has already been stated (A. 1) that such an addition or subtraction would change the species; even as the species of color is changed when a thing from being pale becomes white. If, on the other hand, this addition be understood as applying to the subject, this could only be either because one part of the subject receives a form which it had not previously (thus we may say cold increases in a man who, after being cold in one part of his body, is cold in several parts), or because some other subject is added sharing in the same form (as when a hot thing is added to another, or one white thing to another). But in either of these two ways we have not a more white or a more hot thing, but a greater white or hot thing.
Since, however, as stated above (A. 1), certain accidents are of themselves susceptible of more or less, in some of these we may find increase by addition. For movement increases by an addition either to the time it lasts, or to the course it follows: and yet the species remains the same on account of the oneness of the term. Yet movement increases the intensity as to participation in its subject: i.e. in so far as the same movement can be executed more or less speedily or readily. In like manner, science can increase in itself by addition; thus when anyone learns several conclusions of geometry, the same specific habit of science increases in that man. Yet a man's science increases, as to the subject's participation thereof, in intensity, in so far as one man is quicker and readier than another in considering the same conclusions.
As to bodily habits, it does not seem very probable that they receive increase by way of addition. For an animal is not said to be simply healthy or beautiful, unless it be such in all its parts. And if it be brought to a more perfect measure, this is the result of a change in the simple qualities, which are not susceptible of increase save in intensity on the part of the subject partaking of them.
How this question affects virtues we shall state further on (Q. 66, A. 1).
Reply Obj. 1: Even in bodily bulk increase is twofold. First, by addition of one subject to another; such is the increase of living things. Secondly, by mere intensity, without any addition at all; such is the case with things subject to rarefaction, as is stated in _Phys._ iv, text. 63.
Reply Obj. 2: The cause that increases a habit, always effects something in the subject, but not a new form. But it causes the subject to partake more perfectly of a pre-existing form, or it makes the form to extend further.
Reply Obj. 3: What is not already white, is potentially white, as not yet possessing the form of whiteness: hence the agent causes a new form in the subject. But that which is less hot or white, is not in potentiality to those forms, since it has them already actually: but it is in potentiality to a perfect mode of participation; and this it receives through the agent's action.
Whether Every Act Increases Its Habit?
Objection 1: It would seem that every act increases its habit. For when the cause is increased the effect is increased. Now acts are causes of habits, as stated above (Q. 51, A. 2). Therefore a habit increases when its acts are multiplied.
Obj. 2: Further, of like things a like judgment should be formed. But all the acts proceeding from one and the same habit are alike (Ethic.
ii, 1, 2). Therefore if some acts increase a habit, every act should increase it.
Obj. 3: Further, like is increased by like. But any act is like the habit whence it proceeds. Therefore every act increases the habit.
_On the contrary,_ Opposite effects do not result from the same cause. But according to _Ethic._ ii, 2, some acts lessen the habit whence they proceed, for instance if they be done carelessly.
Therefore it is not every act that increases a habit.
_I answer that,_ "Like acts cause like habits" (Ethic. ii, 1, 2). Now things are like or unlike not only in respect of their qualities being the same or various, but also in respect of the same or a different mode of participation. For it is not only black that is unlike white, but also less white is unlike more white, since there is movement from less white to more white, even as from one opposite to another, as stated in _Phys._ v, text. 52.
But since use of habits depends on the will, as was shown above (Q.
50, A. 5); just as one who has a habit may fail to use it or may act contrary to it; so may he happen to use the habit by performing an act that is not in proportion to the intensity of the habit.
Accordingly, if the intensity of the act correspond in proportion to the intensity of the habit, or even surpass it, every such act either increases the habit or disposes to an increase thereof, if we may speak of the increase of habits as we do of the increase of an animal. For not every morsel of food actually increases the animal's size as neither does every drop of water hollow out the stone: but the multiplication of food results at last in an increase of the body. So, too, repeated acts cause a habit to grow. If, however, the act falls short of the intensity of the habit, such an act does not dispose to an increase of that habit, but rather to a lessening thereof.
From this it is clear how to solve the objections.
QUESTION 53 HOW HABITS ARE CORRUPTED OR DIMINISHED (In Three Articles) We must now consider how habits are lost or weakened; and under this head there are three points of inquiry: (1) Whether a habit can be corrupted?
(2) Whether it can be diminished?
(3) How are habits corrupted or diminished?
Whether a Habit Can Be Corrupted?
Objection 1: It would seem that a habit cannot be corrupted. For habit is within its subject like a second nature; wherefore it is pleasant to act from habit. Now so long as a thing is, its nature is not corrupted. Therefore neither can a habit be corrupted so long as its subject remains.
Obj. 2: Further, whenever a form is corrupted, this is due either to corruption of its subject, or to its contrary: thus sickness ceases through corruption of the animal, or through the advent of health.
Now science, which is a habit, cannot be lost through corruption of its subject: since "the intellect," which is its subject, "is a substance that is incorruptible" (De Anima i, text. 65). In like manner, neither can it be lost through the action of its contrary: since intelligible species are not contrary to one another (Metaph.
vii, text. 52). Therefore the habit of science can nowise be lost.
Obj. 3: Further, all corruption results from some movement. But the habit of science, which is in the soul, cannot be corrupted by a direct movement of the soul itself, since the soul is not moved directly. It is, however, moved indirectly through the movement of the body: and yet no bodily change seems capable of corrupting the intelligible species residing in the intellect: since the intellect independently of the body is the proper abode of the species; for which reason it is held that habits are not lost either through old age or through death. Therefore science cannot be corrupted. For the same reason neither can habits of virtue be corrupted, since they also are in the rational soul, and, as the Philosopher declares (Ethic. i, 10), "virtue is more lasting than learning."
_On the contrary,_ The Philosopher says (De Long. et Brev. Vitae ii) that "forgetfulness and deception are the corruption of science."
Moreover, by sinning a man loses a habit of virtue: and again, virtues are engendered and corrupted by contrary acts (Ethic. ii, 2).
_I answer that,_ A form is said to be corrupted directly by its contrary; indirectly, through its subject being corrupted. When therefore a habit has a corruptible subject, and a cause that has a contrary, it can be corrupted both ways. This is clearly the case with bodily habits--for instance, health and sickness. But those habits that have an incorruptible subject, cannot be corrupted indirectly.
There are, however, some habits which, while residing chiefly in an incorruptible subject, reside nevertheless secondarily in a corruptible subject; such is the habit of science which is chiefly indeed in the "possible" intellect, but secondarily in the sensitive powers of apprehension, as stated above (Q. 50, A. 3, ad 3).
Consequently the habit of science cannot be corrupted indirectly, on the part of the "possible" intellect, but only on the part of the lower sensitive powers.
We must therefore inquire whether habits of this kind can be corrupted directly. If then there be a habit having a contrary, either on the part of itself or on the part of its cause, it can be corrupted directly: but if it has no contrary, it cannot be corrupted directly. Now it is evident that an intelligible species residing in the "possible" intellect, has no contrary; nor can the active intellect, which is the cause of that species, have a contrary.
Wherefore if in the "possible" intellect there be a habit caused immediately by the active intellect, such a habit is incorruptible both directly and indirectly. Such are the habits of the first principles, both speculative and practical, which cannot be corrupted by any forgetfulness or deception whatever: even as the Philosopher says about prudence (Ethic. vi, 5) that "it cannot be lost by being forgotten." There is, however, in the "possible" intellect a habit caused by the reason, to wit, the habit of conclusions, which is called science, to the cause of which something may be contrary in two ways. First, on the part of those very propositions which are the starting point of the reason: for the assertion "Good is not good" is contrary to the assertion "Good is good" (Peri Herm. ii). Secondly, on the part of the process of reasoning; forasmuch as a sophistical syllogism is contrary to a dialectic or demonstrative syllogism.
Wherefore it is clear that a false reason can corrupt the habit of a true opinion or even of science. Hence the Philosopher, as stated above, says that "deception is the corruption of science." As to virtues, some of them are intellectual, residing in reason itself, as stated in _Ethic._ vi, 1: and to these applies what we have said of science and opinion. Some, however, viz. the moral virtues, are in the appetitive part of the soul; and the same may be said of the contrary vices. Now the habits of the appetitive part are caused therein because it is natural to it to be moved by the reason.
Therefore a habit either of virtue or of vice, may be corrupted by a judgment of reason, whenever its motion is contrary to such vice or virtue, whether through ignorance, passion or deliberate choice.
Reply Obj. 1: As stated in _Ethic._ vii, 10, a habit is like a second nature, and yet it falls short of it. And so it is that while the nature of a thing cannot in any way be taken away from a thing, a habit is removed, though with difficulty.
Reply Obj. 2: Although there is no contrary to intelligible species, yet there can be a contrary to assertions and to the process of reason, as stated above.
Reply Obj. 3: Science is not taken away by movement of the body, if we consider the root itself of the habit, but only as it may prove an obstacle to the act of science; in so far as the intellect, in its act, has need of the sensitive powers, which are impeded by corporal transmutation. But the intellectual movement of the reason can corrupt the habit of science, even as regards the very root of the habit. In like manner a habit of virtue can be corrupted.
Nevertheless when it is said that "virtue is more lasting than learning," this must be understood in respect, not of the subject or cause, but of the act: because the use of virtue continues through the whole of life, whereas the use of learning does not.
Whether a Habit Can Diminish?
Objection 1: It would seem that a habit cannot diminish. Because a habit is a simple quality and form. Now a simple thing is possessed either wholly or not at all. Therefore although a habit can be lost it cannot diminish.
Obj. 2: Further, if a thing is befitting an accident, this is by reason either of the accident or of its subject. Now a habit does not become more or less intense by reason of itself; else it would follow that a species might be predicated of its individuals more or less.
And if it can become less intense as to its participation by its subject, it would follow that something is accidental to a habit, proper thereto and not common to the habit and its subject. Now whenever a form has something proper to it besides its subject, that form can be separate, as stated in _De Anima_ i, text. 13. Hence it follows that a habit is a separable form; which is impossible.
Obj. 3: Further, the very notion and nature of a habit as of any accident, is inherence in a subject: wherefore any accident is defined with reference to its subject. Therefore if a habit does not become more or less intense in itself, neither can it in its inherence in its subject: and consequently it will be nowise less intense.
_On the contrary,_ It is natural for contraries to be applicable to the same thing. Now increase and decrease are contraries. Since therefore a habit can increase, it seems that it can also diminish.
_I answer that,_ Habits diminish, just as they increase, in two ways, as we have already explained (Q. 52, A. 1). And since they increase through the same cause as that which engenders them, so too they diminish by the same cause as that which corrupts them: since the diminishing of a habit is the road which leads to its corruption, even as, on the other hand, the engendering of a habit is a foundation of its increase.
Reply Obj. 1: A habit, considered in itself, is a simple form. It is not thus that it is subject to decrease; but according to the different ways in which its subject participates in it. This is due to the fact that the subject's potentiality is indeterminate, through its being able to participate a form in various ways, or to extend to a greater or a smaller number of things.
Reply Obj. 2: This argument would hold, if the essence itself of a habit were nowise subject to decrease. This we do not say; but that a certain decrease in the essence of a habit has its origin, not in the habit, but in its subject.
Reply Obj. 3: No matter how we take an accident, its very notion implies dependence on a subject, but in different ways. For if we take an accident in the abstract, it implies relation to a subject, which relation begins in the accident and terminates in the subject: for "whiteness is that whereby a thing is white." Accordingly in defining an accident in the abstract, we do not put the subject as though it were the first part of the definition, viz. the genus; but we give it the second place, which is that of the difference; thus we say that _simitas_ is "a curvature of the nose." But if we take accidents in the concrete, the relation begins in the subject and terminates in the concrete, the relation begins in the subject and terminates at the accident: for "a white thing" is "something that has whiteness." Accordingly in defining this kind of accident, we place the subject as the genus, which is the first part of a definition; for we say that a _simum_ is a "snub-nose." Accordingly whatever is befitting an accident on the part of the subject, but is not of the very essence of the accident, is ascribed to that accident, not in the abstract, but in the concrete. Such are increase and decrease in certain accidents: wherefore to be more or less white is not ascribed to whiteness but to a white thing. The same applies to habits and other qualities; save that certain habits and other qualities; save that certain habits increase or diminish by a kind of addition, as we have already clearly explained (Q. 52, A. 2).
Whether a Habit Is Corrupted or Diminished Through Mere Cessation from Act?
Objection 1: It would seem that a habit is not corrupted or diminished through mere cessation from act. For habits are more lasting than passion-like qualities, as we have explained above (Q.
corrupted nor diminished by cessation from act: for whiteness is not lessened through not affecting the sight, nor heat through ceasing to make something hot. Therefore neither are habits diminished or corrupted through cessation from act.
Obj. 2: Further, corruption and diminution are changes. Now nothing is changed without a moving cause. Since therefore cessation from act does not imply a moving cause, it does not appear how a habit can be diminished or corrupted through cessation from act.
Obj. 3: Further, the habits of science and virtue are in the intellectual soul which is above time. Now those things that are above time are neither destroyed nor diminished by length of time.
Neither, therefore, are such habits destroyed or diminished through length of time, if one fails for long to exercise them.
_On the contrary,_ The Philosopher says (De Long. et Brev. Vitae ii) that not only "deception," but also "forgetfulness, is the corruption of science." Moreover he says (Ethic. viii, 5) that "want of intercourse has dissolved many a friendship." In like manner other habits of virtue are diminished or destroyed through cessation from act.
_I answer that,_ As stated in _Phys._ vii, text. 27, a thing is a cause of movement in two ways. First, directly; and such a thing causes movement by reason of its proper form; thus fire causes heat.
Secondly, indirectly; for instance, that which removes an obstacle.
It is in this latter way that the destruction or diminution of a habit results through cessation from act, in so far, to wit, as we cease from exercising an act which overcame the causes that destroyed or weakened that habit. For it has been stated (A. 1) that habits are destroyed or diminished directly through some contrary agency.
Consequently all habits that are gradually undermined by contrary agencies which need to be counteracted by acts proceeding from those habits, are diminished or even destroyed altogether by long cessation from act, as is clearly seen in the case both of science and of virtue. For it is evident that a habit of moral virtue makes a man ready to choose the mean in deeds and passions. And when a man fails to make use of his virtuous habit in order to moderate his own passions or deeds, the necessary result is that many passions and deeds fail to observe the mode of virtue, by reason of the inclination of the sensitive appetite and of other external agencies.
Wherefore virtue is destroyed or lessened through cessation from act.
The same applies to the intellectual habits, which render man ready to judge aright of those things that are pictured by his imagination.
Hence when man ceases to make use of his intellectual habits, strange fancies, sometimes in opposition to them, arise in his imagination; so that unless those fancies be, as it were, cut off or kept back by frequent use of his intellectual habits, man becomes less fit to judge aright, and sometimes is even wholly disposed to the contrary, and thus the intellectual habit is diminished or even wholly destroyed by cessation from act.
Reply Obj. 1: Even heat would be destroyed through ceasing to give heat, if, for this same reason, cold which is destructive of heat were to increase.
Reply Obj. 2: Cessation from act is a moving cause, conducive of corruption or diminution, by removing the obstacles thereto, as explained above.
Reply Obj. 3: The intellectual part of the soul, considered in itself, is above time, but the sensitive part is subject to time, and therefore in course of time it undergoes change as to the passions of the sensitive part, and also as to the powers of apprehension. Hence the Philosopher says (Phys. iv. text. 117) that time makes us forget.
QUESTION 54 OF THE DISTINCTION OF HABITS (In Four Articles) We have now to consider the distinction of habits; and under this head there are four points of inquiry: (1) Whether many habits can be in one power?
(2) Whether habits are distinguished by their objects?
(3) Whether habits are divided into good and bad?
(4) Whether one habit may be made up of many habits?
Whether Many Habits Can Be in One Power?
Objection 1: It would seem that there cannot be many habits in one power. For when several things are distinguished in respect of the same thing, if one of them be multiplied, the others are too. Now habits and powers are distinguished in respect of the same thing, viz. their acts and objects. Therefore they are multiplied in like manner. Therefore there cannot be many habits in one power.
Obj. 2: Further, a power is a simple force. Now in one simple subject there cannot be diversity of accidents; for the subject is the cause of its accidents; and it does not appear how diverse effects can proceed from one simple cause. Therefore there cannot be many habits in one power.
Obj. 3: Further, just as the body is informed by its shape, so is a power informed by a habit. But one body cannot be informed at the same time by various shapes. Therefore neither can a power be informed at the same time by many habits. Therefore several habits cannot be at the same time in one power.
_On the contrary,_ The intellect is one power; wherein, nevertheless, are the habits of various sciences.
_I answer that,_ As stated above (Q. 49, A. 4), habits are dispositions of a thing that is in potentiality to something, either to nature, or to operation, which is the end of nature. As to those habits which are dispositions to nature, it is clear that several can be in one same subject: since in one subject we may take parts in various ways, according to the various dispositions of which parts there are various habits. Thus, if we take the humors as being parts of the human body, according to their disposition in respect of human nature, we have the habit or disposition of health: while, if we take like parts, such as nerves, bones, and flesh, the disposition of these in respect of nature is strength or weakness; whereas, if we take the limbs, i.e. the hands, feet, and so on, the disposition of these in proportion to nature, is beauty: and thus there are several habits or dispositions in the same subject.
If, however, we speak of those habits that are dispositions to operation, and belong properly to the powers; thus, again, there may be several habits in one power. The reason for this is that the subject of a habit is a passive power, as stated above (Q. 51, A. 2):