QUESTION 51: OF THE CAUSE OF HABITS, AS TO THEIR FORMATION
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
(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?
Article 1: 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.
Objection 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.
Objection 3: Further, nature does not fail in necessaries. But habits are
necessary in order to act well, as we have stated above (Question , Article ). 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
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 , Article ), 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 , Article ; FP, Question , Article .
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
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
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.
Reply to Objection 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.
Reply to Objection 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.
Article 2: 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 , Article ). 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.
Objection 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
Objection 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.
Reply to Objection 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.
Reply to Objection 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.
Article 3: 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.
Objection 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.
Objection 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
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 ), 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 , Article  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.
Hence the solutions to the objections are clear.
Article 4: 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.
Objection 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 ). Therefore
God does not cause habits to be in man except by acts.
Objection 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 (Ecclus. 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 , Article ).
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 ,
Article . 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.
Reply to Objection 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.
Reply to Objection 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.