[I-II.q.52.a.1.arg.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.

[I-II.q.52.a.1.arg.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.

[I-II.q.52.a.1.arg.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.

[I-II.q.52.a.1.sc] 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-II.q.52.a.1.co] 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 (66, 1) how it is with the virtues.

[I-II.q.52.a.1.ad.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.

[I-II.q.52.a.1.ad.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.

[I-II.q.52.a.1.ad.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).

[I-II.q.52.a.2.arg.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.

[I-II.q.52.a.2.arg.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.

[I-II.q.52.a.2.arg.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.

[I-II.q.52.a.2.sc] 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-II.q.52.a.2.co] 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 (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 (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 (66, 1).

[I-II.q.52.a.2.ad.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.

[I-II.q.52.a.2.ad.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.

[I-II.q.52.a.2.ad.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.

[I-II.q.52.a.3.arg.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 (Question 51, Article 2). Therefore a habit increases when its acts are multiplied.

[I-II.q.52.a.3.arg.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.

[I-II.q.52.a.3.arg.3] Further, like is increased by like. But any act is like the habit whence it proceeds. Therefore every act increases the habit.

[I-II.q.52.a.3.sc] 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-II.q.52.a.3.co] "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 (Question 50, Article 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.

The Summa Theologica of St. Thomas AquinasSecond and Revised Edition, 1920Literally translated by Fathers of the English Dominican ProvinceOnline Edition Copyright © 2009 by Kevin Knight Nihil Obstat. F. Innocentius Apap, O.P., S.T.M., Censor. Theol.Imprimatur. Edus. Canonicus Surmont, Vicarius Generalis. Westmonasterii.APPROBATIO ORDINISNihil Obstat. F. Raphael Moss, O.P., S.T.L. and F. Leo Moore, O.P., S.T.L.Imprimatur. F. Beda Jarrett, O.P., S.T.L., A.M., Prior Provincialis AngliæMARIÆ IMMACULATÆ - SEDI SAPIENTIÆ