[I-II.q.54.a.1.arg.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.

[I-II.q.54.a.1.arg.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.

[I-II.q.54.a.1.arg.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.

[I-II.q.54.a.1.sc] The intellect is one power; wherein, nevertheless, are the habits of various sciences.

[I-II.q.54.a.1.co] As stated above (Question 49, Article 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 (Question 51, Article 2): for it is only an active power that cannot be the subject of a habit, as was clearly shown above (Question 51, Article 2). Now a passive power is compared to the determinate act of any species, as matter to form: because, just as matter is determinate to one form by one agent, so, too, is a passive power determined by the nature of one active object to an act specifically one. Wherefore, just as several objects can move one passive power, so can one passive power be the subject of several acts or perfections specifically diverse. Now habits are qualities or forms adhering to a power, and inclining that power to acts of a determinate species. Consequently several habits, even as several specifically different acts, can belong to one power.

[I-II.q.54.a.1.ad.1] Even as in natural things, diversity of species is according to the form, and diversity of genus, according to matter, as stated in Metaph. v, text. 33 (since things that differ in matter belong to different genera): so, too, generic diversity of objects entails a difference of powers (wherefore the Philosopher says in Ethic. vi, 1, that "those objects that differ generically belong to different departments of the soul"); while specific difference of objects entails a specific difference of acts, and consequently of habits also. Now things that differ in genus differ in species, but not vice versa. Wherefore the acts and habits of different powers differ in species: but it does not follow that different habits are in different powers, for several can be in one power. And even as several genera may be included in one genus, and several species be contained in one species; so does it happen that there are several species of habits and powers.

[I-II.q.54.a.1.ad.2] Although a power is simple as to its essence, it is multiple virtually, inasmuch as it extends to many specifically different acts. Consequently there is nothing to prevent many superficially different habits from being in one power.

[I-II.q.54.a.1.ad.3] A body is informed by its shape as by its own terminal boundaries: whereas a habit is not the terminal boundary of a power, but the disposition of a power to an act as to its ultimate term. Consequently one same power cannot have several acts at the same time, except in so far as perchance one act is comprised in another; just as neither can a body have several shapes, save in so far as one shape enters into another, as a three-sided in a four-sided figure. For the intellect cannot understand several things at the same time "actually"; and yet it can know several things at the same time "habitually."

[I-II.q.54.a.2.arg.1] It would seem that habits are not distinguished by their objects. For contraries differ in species. Now the same habit of science regards contraries: thus medicine regards the healthy and the unhealthy. Therefore habits are not distinguished by objects specifically distinct.

[I-II.q.54.a.2.arg.2] Further, different sciences are different habits. But the same scientific truth belongs to different sciences: thus both the physicist and the astronomer prove the earth to be round, as stated in Phys. ii, text. 17. Therefore habits are not distinguished by their objects.

[I-II.q.54.a.2.arg.3] Further, wherever the act is the same, the object is the same. But the same act can belong to different habits of virtue, if it be directed to different ends; thus to give money to anyone, if it be done for God's sake, is an act of charity; while, if it be done in order to pay a debt, it is an act of justice. Therefore the same object can also belong to different habits. Therefore diversity of habits does not follow diversity of objects.

[I-II.q.54.a.2.sc] Acts differ in species according to the diversity of their objects, as stated above (Question 18, Article 5). But habits are dispositions to acts. Therefore habits also are distinguished according to the diversity of objects.

[I-II.q.54.a.2.co] A habit is both a form and a habit. Hence the specific distinction of habits may be taken in the ordinary way in which forms differ specifically; or according to that mode of distinction which is proper to habits. Accordingly forms are distinguished from one another in reference to the diversity of their active principles, since every agent produces its like in species. Habits, however, imply order to something: and all things that imply order to something, are distinguished according to the distinction of the things to which they are ordained. Now a habit is a disposition implying a twofold order: viz. to nature and to an operation consequent to nature.

Accordingly habits are specifically distinct in respect of three things. First, in respect of the active principles of such dispositions; secondly, in respect of nature; thirdly, in respect of specifically different objects, as will appear from what follows.

[I-II.q.54.a.2.ad.1] In distinguishing powers, or also habits, we must consider the object not in its material but in its formal aspect, which may differ in species or even in genus. And though the distinction between specific contraries is a real distinction yet they are both known under one aspect, since one is known through the other. And consequently in so far as they concur in the one aspect of cognoscibility, they belong to one cognitive habit.

[I-II.q.54.a.2.ad.2] The physicist proves the earth to be round by one means, the astronomer by another: for the latter proves this by means of mathematics, e.g. by the shapes of eclipses, or something of the sort; while the former proves it by means of physics, e.g. by the movement of heavy bodies towards the center, and so forth. Now the whole force of a demonstration, which is "a syllogism producing science," as stated in Poster. i, text. 5, depends on the mean. And consequently various means are as so many active principles, in respect of which the habits of science are distinguished.

[I-II.q.54.a.2.ad.3] As the Philosopher says (Phys. ii, text. 89; Ethic. vii, 8), the end is, in practical matters, what the principle is in speculative matters. Consequently diversity of ends demands a diversity of virtues, even as diversity of active principles does. Moreover the ends are objects of the internal acts, with which, above all, the virtues are concerned, as is evident from what has been said (18, 6; 19, 2, ad 1; 34, 4).

[I-II.q.54.a.3.arg.1] It would seem that habits are not divided into good and bad. For good and bad are contraries. Now the same habit regards contraries, as was stated above (2, Objection 1). Therefore habits are not divided into good and bad.

[I-II.q.54.a.3.arg.2] Further, good is convertible with being; so that, since it is common to all, it cannot be accounted a specific difference, as the Philosopher declares (Topic. iv). Again, evil, since it is a privation and a non-being, cannot differentiate any being. Therefore habits cannot be specifically divided into good and evil.

[I-II.q.54.a.3.arg.3] Further, there can be different evil habits about one same object; for instance, intemperance and insensibility about matters of concupiscence: and in like manner there can be several good habits; for instance, human virtue and heroic or godlike virtue, as the Philosopher clearly states (Ethic. vii, 1). Therefore, habits are not divided into good and bad.

[I-II.q.54.a.3.sc] A good habit is contrary to a bad habit, as virtue to vice. Now contraries are divided specifically into good and bad habits.

[I-II.q.54.a.3.co] As stated above (Article 2), habits are specifically distinct not only in respect of their objects and active principles, but also in their relation to nature. Now, this happens in two ways. First, by reason of their suitableness or unsuitableness to nature. In this way a good habit is specifically distinct from a bad habit: since a good habit is one which disposes to an act suitable to the agent's nature, while an evil habit is one which disposes to an act unsuitable to nature. Thus, acts of virtue are suitable to human nature, since they are according to reason, whereas acts of vice are discordant from human nature, since they are against reason. Hence it is clear that habits are distinguished specifically by the difference of good and bad.

Secondly, habits are distinguished in relation to nature, from the fact that one habit disposes to an act that is suitable to a lower nature, while another habit disposes to an act befitting a higher nature. And thus human virtue, which disposes to an act befitting human nature, is distinct from godlike or heroic virtue, which disposes to an act befitting some higher nature.

[I-II.q.54.a.3.ad.1] The same habit may be about contraries in so far as contraries agree in one common aspect. Never, however, does it happen that contrary habits are in one species: since contrariety of habits follows contrariety of aspect. Accordingly habits are divided into good and bad, namely, inasmuch as one habit is good, and another bad; but not by reason of one habit being something good, and another about something bad.

[I-II.q.54.a.3.ad.2] It is not the good which is common to every being, that is a difference constituting the species of a habit; but some determinate good by reason of suitability to some determinate, viz. the human, nature. In like manner the evil that constitutes a difference of habits is not a pure privation, but something determinate repugnant to a determinate nature.

[I-II.q.54.a.3.ad.3] Several good habits about one same specific thing are distinct in reference to their suitability to various natures, as stated above. But several bad habits in respect of one action are distinct in reference to their diverse repugnance to that which is in keeping with nature: thus, various vices about one same matter are contrary to one virtue.

[I-II.q.54.a.4.arg.1] It would seem that one habit is made up of many habits. For whatever is engendered, not at once, but little by little, seems to be made up of several parts. But a habit is engendered, not at once, but little by little out of several acts, as stated above (Question 51, Article 3). Therefore one habit is made up of several.

[I-II.q.54.a.4.arg.2] Further, a whole is made up of its parts. Now many parts are assigned to one habit: thus Tully assigns many parts of fortitude, temperance, and other virtues. Therefore one habit is made up of many.

[I-II.q.54.a.4.arg.3] Further, one conclusion suffices both for an act and for a habit of scientific knowledge. But many conclusions belong to but one science, to geometry, for instance, or to arithmetic. Therefore one habit is made up of many.

[I-II.q.54.a.4.sc] A habit, since it is a quality, is a simple form. But nothing simple is made up of many. Therefore one habit is not made up of many.

[I-II.q.54.a.4.co] A habit directed to operation, such as we are chiefly concerned with at present, is a perfection of a power. Now every perfection should be in proportion with that which it perfects. Hence, just as a power, while it is one, extends to many things, in so far as they have something in common, i.e. some general objective aspect, so also a habit extends to many things, in so far as they are related to one, for instance, to some specific objective aspect, or to one nature, or to one principle, as was clearly stated above (2,3).

If then we consider a habit as to the extent of its object, we shall find a certain multiplicity therein. But since this multiplicity is directed to one thing, on which the habit is chiefly intent, hence it is that a habit is a simple quality, not composed to several habits, even though it extend to many things. For a habit does not extend to many things save in relation to one, whence it derives its unity.

[I-II.q.54.a.4.ad.1] That a habit is engendered little by little, is due, not to one part being engendered after another, but to the fact that the subject does not acquire all at once a firm and difficultly changeable disposition; and also to the fact that it begins by being imperfectly in the subject, and is gradually perfected. The same applies to other qualities.

[I-II.q.54.a.4.ad.2] The parts which are assigned to each cardinal virtue, are not integral parts that combine to form a whole; but subjective or potential parts, as we shall explain further on (57, 6, ad 4; II-II, 48).

[I-II.q.54.a.4.ad.3] In any science, he who acquires, by demonstration, scientific knowledge of one conclusion, has the habit indeed, yet imperfectly. And when he obtains, by demonstration, the scientific knowledge of another conclusion, no additional habit is engendered in him: but the habit which was in him previously is perfected, forasmuch as it has increased in extent; because the conclusions and demonstrations of one science are coordinate, and one flows from another.

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