Summa Th. I-II EN Qu.51


We must next consider the cause of habits: and firstly, as to their formation; secondly, as to their increase; thirdly, as to their diminution and corruption. Under the first head there are four points of inquiry:

(1) Whether any habit is from nature?

(2) Whether any habit is caused by acts?

(3) Whether any habit can be caused by one act?

(4) Whether any habits are infused in man by God?

Whether any habit is from nature?


Objection: 1. It would seem that no habit is from nature. For the use of those things which are from nature does not depend on the will. But habit "is that which we use when we will," as the Commentator says on De Anima iii. Therefore habit is not from nature.
2. Further, nature does not employ two where one is sufficient. But the powers of the soul are from nature. If therefore the habits of the powers were from nature, habit and power would be one.
3. Further, nature does not fail in necessaries. But habits are necessary in order to act well, as we have stated above (Question [49], Article [4]). If therefore any habits were from nature, it seems that nature would not fail to cause all necessary habits: but this is clearly false. Therefore habits are not from nature.

On the contrary In Ethic. vi, 6, among other habits, place is given to understanding of first principles, which habit is from nature: wherefore also first principles are said to be known naturally.
I answer that One thing can be natural to another in two ways. First in respect of the specific nature, as the faculty of laughing is natural to man, and it is natural to fire to have an upward tendency. Secondly, in respect of the individual nature, as it is natural to Socrates or Plato to be prone to sickness or inclined to health, in accordance with their respective temperaments. Again, in respect of both natures, something may be called natural in two ways: first, because it entirely is from the nature; secondly, because it is partly from nature, and partly from an extrinsic principle. For instance, when a man is healed by himself, his health is entirely from nature; but when a man is healed by means of medicine, health is partly from nature, partly from an extrinsic principle.Thus, then, if we speak of habit as a disposition of the subject in relation to form or nature, it may be natural in either of the foregoing ways. For there is a certain natural disposition demanded by the human species, so that no man can be without it. And this disposition is natural in respect of the specific nature. But since such a disposition has a certain latitude, it happens that different grades of this disposition are becoming to different men in respect of the individual nature. And this disposition may be either entirely from nature, or partly from nature, and partly from an extrinsic principle, as we have said of those who are healed by means of art.But the habit which is a disposition to operation, and whose subject is a power of the soul, as stated above (Question [50], Article [2]), may be natural whether in respect of the specific nature or in respect of the individual nature: in respect of the specific nature, on the part of the soul itself, which, since it is the form of the body, is the specific principle; but in respect of the individual nature, on the part of the body, which is the material principle. Yet in neither way does it happen that there are natural habits in man, so that they be entirely from nature. In the angels, indeed, this does happen, since they have intelligible species naturally impressed on them, which cannot be said of the human soul, as we have said in the FP, Question [55], Article [2]; FP, Question [84], Article [3].There are, therefore, in man certain natural habits, owing their existence, partly to nature, and partly to some extrinsic principle: in one way, indeed, in the apprehensive powers; in another way, in the appetitive powers. For in the apprehensive powers there may be a natural habit by way of a beginning, both in respect of the specific nature, and in respect of the individual nature. This happens with regard to the specific nature, on the part of the soul itself: thus the understanding of first principles is called a natural habit. For it is owing to the very nature of the intellectual soul that man, having once grasped what is a whole and what is a part, should at once perceive that every whole is larger than its part: and in like manner with regard to other such principles. Yet what is a whole, and what is a part---this he cannot know except through the intelligible species which he has received from phantasms: and for this reason, the Philosopher at the end of the Posterior Analytics shows that knowledge of principles comes to us from the senses.But in respect of the individual nature, a habit of knowledge is natural as to its beginning, in so far as one man, from the disposition of his organs of sense, is more apt than another to understand well, since we need the sensitive powers for the operation of the intellect.In the appetitive powers, however, no habit is natural in its beginning, on the part of the soul itself, as to the substance of the habit; but only as to certain principles thereof, as, for instance, the principles of common law are called the "nurseries of virtue." The reason of this is because the inclination to its proper objects, which seems to be the beginning of a habit, does not belong to the habit, but rather to the very nature of the powers.But on the part of the body, in respect of the individual nature, there are some appetitive habits by way of natural beginnings. For some are disposed from their own bodily temperament to chastity or meekness or such like.

Reply to Objection: 1. This objection takes nature as divided against reason and will; whereas reason itself and will belong to the nature of man.
2. Something may be added even naturally to the nature of a power, while it cannot belong to the power itself. For instance, with regard to the angels, it cannot belong to the intellective power itself capable of knowing all things: for thus it would have to be the act of all things, which belongs to God alone. Because that by which something is known, must needs be the actual likeness of the thing known: whence it would follow, if the power of the angel knew all things by itself, that it was the likeness and act of all things. Wherefore there must needs be added to the angels' intellective power, some intelligible species, which are likenesses of things understood: for it is by participation of the Divine wisdom and not by their own essence, that their intellect can be actually those things which they understand. And so it is clear that not everything belonging to a natural habit can belong to the power.
3. Nature is not equally inclined to cause all the various kinds of habits: since some can be caused by nature, and some not, as we have said above. And so it does not follow that because some habits are natural, therefore all are natural.

Whether any habit is caused by acts?

Objection: 1. It would seem that no habit is caused by acts. For habit is a quality, as we have said above (Question [49], Article [1]). Now every quality is caused in a subject, according to the latter's receptivity. Since then the agent, inasmuch as it acts, does not receive but rather gives: it seems impossible for a habit to be caused in an agent by its own acts.
2. Further, the thing wherein a quality is caused is moved to that quality, as may be clearly seen in that which is heated or cooled: whereas that which produces the act that causes the quality, moves, as may be seen in that which heats or cools. If therefore habits were caused in anything by its own act, it would follow that the same would be mover and moved, active and passive: which is impossible, as stated in Physics iii, 8.
3. Further, the effect cannot be more noble than its cause. But habit is more noble than the act which precedes the habit; as is clear from the fact that the latter produces more noble acts. Therefore habit cannot be caused by an act which precedes the habit.

On the contrary The Philosopher (Ethic. ii, 1,2) teaches that habits of virtue and vice are caused by acts.
I answer that In the agent there is sometimes only the active principle of its act: for instance in fire there is only the active principle of heating. And in such an agent a habit cannot be caused by its own act: for which reason natural things cannot become accustomed or unaccustomed, as is stated in Ethic. ii, 1. But a certain agent is to be found, in which there is both the active and the passive principle of its act, as we see in human acts. For the acts of the appetitive power proceed from that same power according as it is moved by the apprehensive power presenting the object: and further, the intellective power, according as it reasons about conclusions, has, as it were, an active principle in a self-evident proposition. Wherefore by such acts habits can be caused in their agents; not indeed with regard to the first active principle, but with regard to that principle of the act, which principle is a mover moved. For everything that is passive and moved by another, is disposed by the action of the agent; wherefore if the acts be multiplied a certain quality is formed in the power which is passive and moved, which quality is called a habit: just as the habits of moral virtue are caused in the appetitive powers, according as they are moved by the reason, and as the habits of science are caused in the intellect, according as it is moved by first propositions.

Reply to Objection: 1. The agent, as agent, does not receive anything. But in so far as it moves through being moved by another, it receives something from that which moves it: and thus is a habit caused.
2. The same thing, and in the same respect, cannot be mover and moved; but nothing prevents a thing from being moved by itself as to different respects, as is proved in Physics viii, text. 28,29.
3. The act which precedes the habit, in so far as it comes from an active principle, proceeds from a more excellent principle than is the habit caused thereby: just as the reason is a more excellent principle than the habit of moral virtue produced in the appetitive power by repeated acts, and as the understanding of first principles is a more excellent principle than the science of conclusions.

Whether a habit can be caused by one act?

Objection: 1. It would seem that a habit can be caused by one act. For demonstration is an act of reason. But science, which is the habit of one conclusion, is caused by one demonstration. Therefore habit can be caused by one act.
2. Further, as acts happen to increase by multiplication so do they happen to increase by intensity. But a habit is caused by multiplication of acts. Therefore also if an act be very intense, it can be the generating cause of a habit.
3. Further, health and sickness are habits. But it happens that a man is healed or becomes ill, by one act. Therefore one act can cause a habit.

On the contrary The Philosopher (Ethic. i, 7): "As neither does one swallow nor one day make spring: so neither does one day nor a short time make a man blessed and happy." But "happiness is an operation in respect of a habit of perfect virtue" (Ethic. i, 7,10,13). Therefore a habit of virtue, and for the same reason, other habits, is not caused by one act.
I answer that As we have said already (Article [2]), habit is caused by act, because a passive power is moved by an active principle. But in order that some quality be caused in that which is passive the active principle must entirely overcome the passive. Whence we see that because fire cannot at once overcome the combustible, it does not enkindle at once; but it gradually expels contrary dispositions, so that by overcoming it entirely, it may impress its likeness on it. Now it is clear that the active principle which is reason, cannot entirely overcome the appetitive power in one act: because the appetitive power is inclined variously, and to many things; while the reason judges in a single act, what should be willed in regard to various aspects and circumstances. Wherefore the appetitive power is not thereby entirely overcome, so as to be inclined like nature to the same thing, in the majority of cases; which inclination belongs to the habit of virtue. Therefore a habit of virtue cannot be caused by one act, but only by many.But in the apprehensive powers, we must observe that there are two passive principles: one is the "possible" [*See FP, Question [79], Article [2] ad 2] intellect itself; the other is the intellect which Aristotle (De Anima iii, text. 20) calls "passive," and is the "particular reason," that is the cogitative power, with memory and imagination. With regard then to the former passive principle, it is possible for a certain active principle to entirely overcome, by one act, the power of its passive principle: thus one self-evident proposition convinces the intellect, so that it gives a firm assent to the conclusion, but a probable proposition cannot do this. Wherefore a habit of opinion needs to be caused by many acts of the reason, even on the part of the "possible" intellect: whereas a habit of science can be caused by a single act of the reason, so far as the "possible" intellect is concerned. But with regard to the lower apprehensive powers, the same acts need to be repeated many times for anything to be firmly impressed on the memory. And so the Philosopher says (De Memor. et Remin. 1) that "meditation strengthens memory." Bodily habits, however, can be caused by one act, if the active principle is of great power: sometimes, for instance, a strong dose of medicine restores health at once.

Reply to Objection: 1. Hence the solutions to the objections are clear.

Whether any habits are infused in man by God?

Objection: 1. It would seem that no habit is infused in man by God. For God treats all equally. If therefore He infuses habits into some, He would infuse them into all: which is clearly untrue.
2. Further, God works in all things according to the mode which is suitable to their nature: for "it belongs to Divine providence to preserve nature," as Dionysius says (Div. Nom. iv). But habits are naturally caused in man by acts, as we have said above (Article [2]). Therefore God does not cause habits to be in man except by acts.
3. Further, if any habit be infused into man by God, man can by that habit perform many acts. But "from those acts a like habit is caused" (Ethic. ii, 1,2). Consequently there will be two habits of the same species in the same man, one acquired, the other infused. Now this seems impossible: for the two forms of the same species cannot be in the same subject. Therefore a habit is not infused into man by God.

On the contrary it is written (Si 15,5): "God filled him with the spirit of wisdom and understanding." Now wisdom and understanding are habits. Therefore some habits are infused into man by God.
I answer that Some habits are infused by God into man, for two reasons.The first reason is because there are some habits by which man is disposed to an end which exceeds the proportion of human nature, namely, the ultimate and perfect happiness of man, as stated above (Question [5], Article [5]). And since habits need to be in proportion with that to which man is disposed by them, therefore is it necessary that those habits, which dispose to this end, exceed the proportion of human nature. Wherefore such habits can never be in man except by Divine infusion, as is the case with all gratuitous virtues.The other reason is, because God can produce the effects of second causes, without these second causes, as we have said in the FP, Question [105], Article [6]. Just as, therefore, sometimes, in order to show His power, He causes health, without its natural cause, but which nature could have caused, so also, at times, for the manifestation of His power, He infuses into man even those habits which can be caused by a natural power. Thus He gave to the apostles the science of the Scriptures and of all tongues, which men can acquire by study or by custom, but not so perfectly.

Reply to Objection: 1. God, in respect of His Nature, is the same to all, but in respect of the order of His Wisdom, for some fixed motive, gives certain things to some, which He does not give to others.
2. That God works in all according to their mode, does not hinder God from doing what nature cannot do: but it follows from this that He does nothing contrary to that which is suitable to nature.
3. Acts produced by an infused habit, do not cause a habit, but strengthen the already existing habit; just as the remedies of medicine given to a man who is naturally health, do not cause a kind of health, but give new strength to the health he had before.


We have now to consider the increase of habits; under which head there are three points of inquiry:

(1) Whether habits increase?

(2) Whether they increase by addition?

(3) Whether each act increases the habit?

Whether habits increase?

Objection: 1. It would seem that habits cannot increase. For increase concerns quantity (Phys. v, text. 18). But habits are not in the genus quantity, but in that of quality. Therefore there can be no increase of habits.
2. Further, habit is a perfection (Phys. vii, text. 17,18). But since perfection conveys a notion of end and term, it seems that it cannot be more or less. Therefore a habit cannot increase.
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 (Lc 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, 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 (Question [66], Article [1]) how it is with the virtues.

Reply to Objection: 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.
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.
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 habits 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.
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.
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 (Article [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 (Article [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 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 (Article [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 (Question [66], Article [1]).

Reply to Objection: 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.
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.
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.

Summa Th. I-II EN Qu.51