Summa Th. I-II EN Qu.5 a.4

Whether happiness once had can be lost?

Objection: 1. It would seem that Happiness can be lost. For Happiness is a perfection. But every perfection is in the thing perfected according to the mode of the latter. Since then man is, by his nature, changeable, it seems that Happiness is participated by man in a changeable manner. And consequently it seems that man can lose Happiness.
2. Further, Happiness consists in an act of the intellect; and the intellect is subject to the will. But the will can be directed to opposites. Therefore it seems that it can desist from the operation whereby man is made happy: and thus man will cease to be happy.
3. Further, the end corresponds to the beginning. But man's Happiness has a beginning, since man was not always happy. Therefore it seems that it has an end.

On the contrary It is written (Mt 25,46) of the righteous that "they shall god . . . into life everlasting," which, as above stated (Article [2]), is the Happiness of the saints. Now what is eternal ceases not. Therefore Happiness cannot be lost.
I answer that If we speak of imperfect happiness, such as can be had in this life, in this sense it can be lost. This is clear of contemplative happiness, which is lost either by forgetfulness, for instance, when knowledge is lost through sickness; or again by certain occupations, whereby a man is altogether withdrawn from contemplation.This is also clear of active happiness: since man's will can be changed so as to fall to vice from the virtue, in whose act that happiness principally consists. If, however, the virtue remain unimpaired, outward changes can indeed disturb such like happiness, in so far as they hinder many acts of virtue; but they cannot take it away altogether because there still remains an act of virtue, whereby man bears these trials in a praiseworthy manner. And since the happiness of this life can be lost, a circumstance that appears to be contrary to the nature of happiness, therefore did the Philosopher state (Ethic. i, 10) that some are happy in this life, not simply, but "as men," whose nature is subject to change.But if we speak of that perfect Happiness which we await after this life, it must be observed that Origen (Peri Archon. ii, 3), following the error of certain Platonists, held that man can become unhappy after the final Happiness.This, however, is evidently false, for two reasons. First, from the general notion of happiness. For since happiness is the "perfect and sufficient good," it must needs set man's desire at rest and exclude every evil. Now man naturally desires to hold to the good that he has, and to have the surety of his holding: else he must of necessity be troubled with the fear of losing it, or with the sorrow of knowing that he will lose it. Therefore it is necessary for true Happiness that man have the assured opinion of never losing the good that he possesses. If this opinion be true, it follows that he never will lose happiness: but if it be false, it is in itself an evil that he should have a false opinion: because the false is the evil of the intellect, just as the true is its good, as stated in Ethic. vi, 2. Consequently he will no longer be truly happy, if evil be in him.Secondly, it is again evident if we consider the specific nature of Happiness. For it has been shown above (Question [3], Article [8]) that man's perfect Happiness consists in the vision of the Divine Essence. Now it is impossible for anyone seeing the Divine Essence, to wish not to see It. Because every good that one possesses and yet wishes to be without, is either insufficient, something more sufficing being desired in its stead; or else has some inconvenience attached to it, by reason of which it becomes wearisome. But the vision of the Divine Essence fills the soul with all good things, since it unites it to the source of all goodness; hence it is written (Ps 16,15): "I shall be satisfied when Thy glory shall appear"; and (Sg 7,11): "All good things came to me together with her," i.e. with the contemplation of wisdom. In like manner neither has it any inconvenience attached to it; because it is written of the contemplation of wisdom (Sg 8,16): "Her conversation hath no bitterness, nor her company any tediousness." It is thus evident that the happy man cannot forsake Happiness of his own accord. Moreover, neither can he lose Happiness, through God taking it away from him. Because, since the withdrawal of Happiness is a punishment, it cannot be enforced by God, the just Judge, except for some fault; and he that sees God cannot fall into a fault, since rectitude of the will, of necessity, results from that vision as was shown above (Question [4], Article [4]). Nor again can it be withdrawn by any other agent. Because the mind that is united to God is raised above all other things: and consequently no other agent can sever the mind from that union. Therefore it seems unreasonable that as time goes on, man should pass from happiness to misery, and vice versa; because such like vicissitudes of time can only be for such things as are subject to time and movement.

Reply to Objection: 1. Happiness is consummate perfection, which excludes every defect from the happy. And therefore whoever has happiness has it altogether unchangeably: this is done by the Divine power, which raises man to the participation of eternity which transcends all change.
2. The will can be directed to opposites, in things which are ordained to the end; but it is ordained, of natural necessity, to the last end. This is evident from the fact that man is unable not to wish to be happy.
3. Happiness has a beginning owing to the condition of the participator: but it has no end by reason of the condition of the good, the participation of which makes man happy. Hence the beginning of happiness is from one cause, its endlessness is from another.

Whether man can attain happiness by his natural powers?

Objection: 1. It would seem that man can attain Happiness by his natural powers. For nature does not fail in necessary things. But nothing is so necessary to man as that by which he attains the last end. Therefore this is not lacking to human nature. Therefore man can attain Happiness by his natural powers.
2. Further, since man is more noble than irrational creatures, it seems that he must be better equipped than they. But irrational creatures can attain their end by their natural powers. Much more therefore can man attain Happiness by his natural powers.
3. Further, Happiness is a "perfect operation," according to the Philosopher (Ethic. vii, 13). Now the beginning of a thing belongs to the same principle as the perfecting thereof. Since, therefore, the imperfect operation, which is as the beginning in human operations, is subject to man's natural power, whereby he is master of his own actions; it seems that he can attain to perfect operation, i.e. Happiness, by his natural powers.

On the contrary Man is naturally the principle of his action, by his intellect and will. But final Happiness prepared for the saints, surpasses the intellect and will of man; for the Apostle says (1Co 2,9) "Eye hath not seen, nor ear heard, neither hath it entered into the heart of man, what things God hath prepared for them that love Him." Therefore man cannot attain Happiness by his natural powers.
I answer that Imperfect happiness that can be had in this life, can be acquired by man by his natural powers, in the same way as virtue, in whose operation it consists: on this point we shall speak further on (Question [63]). But man's perfect Happiness, as stated above (Question [3], Article [8]), consists in the vision of the Divine Essence. Now the vision of God's Essence surpasses the nature not only of man, but also of every creature, as was shown in the FP, Question [12], Article [4]. For the natural knowledge of every creature is in keeping with the mode of his substance: thus it is said of the intelligence (De Causis; Prop. viii) that "it knows things that are above it, and things that are below it, according to the mode of its substance." But every knowledge that is according to the mode of created substance, falls short of the vision of the Divine Essence, which infinitely surpasses all created substance. Consequently neither man, nor any creature, can attain final Happiness by his natural powers.

Reply to Objection: 1. Just as nature does not fail man in necessaries, although it has not provided him with weapons and clothing, as it provided other animals, because it gave him reason and hands, with which he is able to get these things for himself; so neither did it fail man in things necessary, although it gave him not the wherewithal to attain Happiness: since this it could not do. But it did give him free-will, with which he can turn to God, that He may make him happy. "For what we do by means of our friends, is done, in a sense, by ourselves" (Ethic. iii, 3).
2. The nature that can attain perfect good, although it needs help from without in order to attain it, is of more noble condition than a nature which cannot attain perfect good, but attains some imperfect good, although it need no help from without in order to attain it, as the Philosopher says (De Coel. ii, 12). Thus he is better disposed to health who can attain perfect health, albeit by means of medicine, than he who can attain but imperfect health, without the help of medicine. And therefore the rational creature, which can attain the perfect good of happiness, but needs the Divine assistance for the purpose, is more perfect than the irrational creature, which is not capable of attaining this good, but attains some imperfect good by its natural powers.
3. When imperfect and perfect are of the same species, they can be caused by the same power. But this does not follow of necessity, if they be of different species: for not everything, that can cause the disposition of matter, can produce the final perfection. Now the imperfect operation, which is subject to man's natural power, is not of the same species as that perfect operation which is man's happiness: since operation takes its species from its object. Consequently the argument does not prove.

Whether man attains happiness through the action of some higher creature?

Objection: 1. It would seem that man can be made happy through the action of some higher creature, viz. an angel. For since we observe a twofold order in things---one, of the parts of the universe to one another, the other, of the whole universe to a good which is outside the universe; the former order is ordained to the second as to its end (Metaph. xii, 10). Thus the mutual order of the parts of an army is dependent on the order of the parts of an army is dependent on the order of the whole army to the general. But the mutual order of the parts of the universe consists in the higher creatures acting on the lower, as stated in the FP, Question [109], Article [2]: while happiness consists in the order of man to a good which is outside the universe, i.e. God. Therefore man is made happy, through a higher creature, viz. an angel, acting on him.
2. Further, that which is such in potentiality, can be reduced to act, by that which is such actually: thus what is potentially hot, is made actually hot, by something that is actually hot. But man is potentially happy. Therefore he can be made actually happy by an angel who is actually happy.
3. Further, Happiness consists in an operation of the intellect as stated above (Question [3], Article [4]). But an angel can enlighten man's intellect as shown in the FP, Question [111], Article [1]. Therefore an angel can make a man happy.

On the contrary It is written (Ps 83,12): "The Lord will give grace and glory."
I answer that Since every creature is subject to the laws of nature, from the very fact that its power and action are limited: that which surpasses created nature, cannot be done by the power of any creature. Consequently if anything need to be done that is above nature, it is done by God immediately; such as raising the dead to life, restoring sight to the blind, and such like. Now it has been shown above (Article [5]) that Happiness is a good surpassing created nature. Therefore it is impossible that it be bestowed through the action of any creature: but by God alone is man made happy, if we speak of perfect Happiness. If, however, we speak of imperfect happiness, the same is to be said of it as of the virtue, in whose act it consists.

Reply to Objection: 1. It often happens in the case of active powers ordained to one another, that it belongs to the highest power to reach the last end, while the lower powers contribute to the attainment of that last end, by causing a disposition thereto: thus to the art of sailing, which commands the art of shipbuilding, it belongs to use a ship for the end for which it was made. Thus, too, in the order of the universe, man is indeed helped by the angels in the attainment of his last end, in respect of certain preliminary dispositions thereto: whereas he attains the last end itself through the First Agent, which is God.
2. When a form exists perfectly and naturally in something, it can be the principle of action on something else: for instance a hot thing heats through heat. But if a form exist in something imperfectly, and not naturally, it cannot be the principle whereby it is communicated to something else: thus the "intention" of color which is in the pupil, cannot make a thing white; nor indeed can everything enlightened or heated give heat or light to something else; for if they could, enlightening and heating would go on to infinity. But the light of glory, whereby God is seen, is in God perfectly and naturally; whereas in any creature, it is imperfectly and by likeness or participation. Consequently no creature can communicate its Happiness to another.
3. A happy angel enlightens the intellect of a man or of a lower angel, as to certain notions of the Divine works: but not as to the vision of the Divine Essence, as was stated in the FP, Question [106], Article [1]: since in order to see this, all are immediately enlightened by God.

Whether any good works are necessary that man may receive happiness from God?

Objection: 1. It would seem that no works of man are necessary that he may obtain Happiness from God. For since God is an agent of infinite power, He requires before acting, neither matter, nor disposition of matter, but can forthwith produce the whole effect. But man's works, since they are not required for Happiness, as the efficient cause thereof, as stated above (Article [6]), can be required only as dispositions thereto. Therefore God who does not require dispositions before acting, bestows Happiness without any previous works.
2. Further, just as God is the immediate cause of Happiness, so is He the immediate cause of nature. But when God first established nature, He produced creatures without any previous disposition or action on the part of the creature, but made each one perfect forthwith in its species. Therefore it seems that He bestows Happiness on man without any previous works.
3. Further, the Apostle says (Rm 4,6) that Happiness is of the man "to whom God reputeth justice without works." Therefore no works of man are necessary for attaining Happiness.

On the contrary It is written (Jn 13,17): "If you know these things, you shall be blessed if you do them." Therefore Happiness is obtained through works.
I answer that Rectitude of the will, as stated above (Question [4], Article [4]), is necessary for Happiness; since it is nothing else than the right order of the will to the last end; and it is therefore necessary for obtaining the end, just as the right disposition of matter, in order to receive the form. But this does not prove that any work of man need precede his Happiness: for God could make a will having a right tendency to the end, and at the same time attaining the end; just as sometimes He disposes matter and at the same time introduces the form. But the order of Divine wisdom demands that it should not be thus; for as is stated in De Coel. ii, 12, "of those things that have a natural capacity for the perfect good, one has it without movement, some by one movement, some by several." Now to possess the perfect good without movement, belongs to that which has it naturally: and to have Happiness naturally belongs to God alone. Therefore it belongs to God alone not to be moved towards Happiness by any previous operation. Now since Happiness surpasses every created nature, no pure creature can becomingly gain Happiness, without the movement of operation, whereby it tends thereto. But the angel, who is above man in the natural order, obtained it, according to the order of Divine wisdom, by one movement of a meritorious work, as was explained in the FP, Question [62], Article [5]; whereas man obtains it by many movements of works which are called merits. Wherefore also according to the Philosopher (Ethic. i, 9), happiness is the reward of works of virtue.

Reply to Objection: 1. Works are necessary to man in order to gain Happiness; not on account of the insufficiency of the Divine power which bestows Happiness, but that the order in things be observed.
2. God produced the first creatures so that they are perfect forthwith, without any previous disposition or operation of the creature; because He instituted the first individuals of the various species, that through them nature might be propagated to their progeny. In like manner, because Happiness was to be bestowed on others through Christ, who is God and Man, "Who," according to He 2,10, "had brought many children into glory"; therefore, from the very beginning of His conception, His soul was happy, without any previous meritorious operation. But this is peculiar to Him: for Christ's merit avails baptized children for the gaining of Happiness, though they have no merits of their own; because by Baptism they are made members of Christ.
3. The Apostle is speaking of the Happiness of Hope, which is bestowed on us by sanctifying grace, which is not given on account of previous works. For grace is not a term of movement, as Happiness is; rather is it the principle of the movement that tends towards Happiness.

Whether every man desires happiness?

Objection: 1. It would seem that not all desire Happiness. For no man can desire what he knows not; since the apprehended good is the object of the appetite (De Anima iii, 10). But many know not what Happiness is. This is evident from the fact that, as Augustine says (De Trin. xiii, 4), "some thought that Happiness consists in pleasures of the body; some, in a virtue of the soul; some in other things." Therefore not all desire Happiness.
2. Further, the essence of Happiness is the vision of the Divine Essence, as stated above (Question [3], Article [8]). But some consider it impossible for man to see the Divine Essence; wherefore they desire it not. Therefore all men do not desire Happiness.
3. Further, Augustine says (De Trin. xiii, 5) that "happy is he who has all he desires, and desires nothing amiss." But all do not desire this; for some desire certain things amiss, and yet they wish to desire such things. Therefore all do not desire Happiness.

On the contrary Augustine says (De Trin. xiii, 3): "If that actor had said: 'You all wish to be happy; you do not wish to be unhappy,' he would have said that which none would have failed to acknowledge in his will." Therefore everyone desires to be happy.
I answer that Happiness can be considered in two ways. First according to the general notion of happiness: and thus, of necessity, every man desires happiness. For the general notion of happiness consists in the perfect good, as stated above (Articles [3],4). But since good is the object of the will, the perfect good of a man is that which entirely satisfies his will. Consequently to desire happiness is nothing else than to desire that one's will be satisfied. And this everyone desires. Secondly we may speak of Happiness according to its specific notion, as to that in which it consists. And thus all do not know Happiness; because they know not in what thing the general notion of happiness is found. And consequently, in this respect, not all desire it.

Reply to Objection: 1. Wherefore the reply to the first Objection is clear.
2. Since the will follows the apprehension of the intellect or reason; just as it happens that where there is no real distinction, there may be a distinction according to the consideration of reason; so does it happen that one and the same thing is desired in one way, and not desired in another. So that happiness may be considered as the final and perfect good, which is the general notion of happiness: and thus the will naturally and of necessity tends thereto, as stated above. Again it can be considered under other special aspects, either on the part of the operation itself, or on the part of the operating power, or on the part of the object; and thus the will does not tend thereto of necessity.
3. This definition of Happiness given by some---"Happy is the man that has all he desires," or, "whose every wish is fulfilled" is a good and adequate definition; but an inadequate definition if understood in another. For if we understand it simply of all that man desires by his natural appetite, thus it is true that he who has all that he desires, is happy: since nothing satisfies man's natural desire, except the perfect good which is Happiness. But if we understand it of those things that man desires according to the apprehension of the reason, thus it does not belong to Happiness, to have certain things that man desires; rather does it belong to unhappiness, in so far as the possession of such things hinders man from having all that he desires naturally; thus it is that reason sometimes accepts as true things that are a hindrance to the knowledge of truth. And it was through taking this into consideration that Augustine added so as to include perfect Happiness---that he "desires nothing amiss": although the first part suffices if rightly understood, to wit, that "happy is he who has all he desires."



Since therefore Happiness is to be gained by means of certain acts, we must in due sequence consider human acts, in order to know by what acts we may obtain Happiness, and by what acts we are prevented from obtaining it. But because operations and acts are concerned with things singular, consequently all practical knowledge is incomplete unless it take account of things in detail. The study of Morals, therefore, since it treats of human acts, should consider first the general principles; and secondly matters of detail.

In treating of the general principles, the points that offer themselves for our consideration are (1) human acts themselves; (2) their principles. Now of human acts some are proper to man; others are common to man and animals. And since Happiness is man's proper good, those acts which are proper to man have a closer connection with Happiness than have those which are common to man and the other animals. First, then, we must consider those acts which are proper to man; secondly, those acts which are common to man and the other animals, and are called Passions. The first of these points offers a twofold consideration: (1) What makes a human act? (2) What distinguishes human acts?

And since those acts are properly called human which are voluntary, because the will is the rational appetite, which is proper to man; we must consider acts in so far as they are voluntary.

First, then, we must consider the voluntary and involuntary in general; secondly, those acts which are voluntary, as being elicited by the will, and as issuing from the will immediately; thirdly, those acts which are voluntary, as being commanded by the will, which issue from the will through the medium of the other powers.

And because voluntary acts have certain circumstances, according to which we form our judgment concerning them, we must first consider the voluntary and the involuntary, and afterwards, the circumstances of those acts which are found to be voluntary or involuntary. Under the first head there are eight points of inquiry:

(1) Whether there is anything voluntary in human acts?

(2) Whether in irrational animals?

(3) Whether there can be voluntariness without any action?

(4) Whether violence can be done to the will?

(5) Whether violence causes involuntariness?

(6) Whether fear causes involuntariness?

(7) Whether concupiscence causes involuntariness?

(8) Whether ignorance causes involuntariness?

Whether there is anything voluntary in human acts?

Objection: 1. It would seem that there is nothing voluntary in human acts. For that is voluntary "which has its principle within itself." as Gregory of Nyssa [*Nemesius, De Natura Hom. xxxii.], Damascene (De Fide Orth. ii, 24), and Aristotle (Ethic. iii, 1) declare. But the principle of human acts is not in man himself, but outside him: since man's appetite is moved to act, by the appetible object which is outside him, and is as a "mover unmoved" (De Anima iii, 10). Therefore there is nothing voluntary in human acts.
2. Further, the Philosopher (Phys. viii, 2) proves that in animals no new movement arises that is not preceded by a motion from without. But all human acts are new, since none is eternal. Consequently, the principle of all human acts is from without: and therefore there is nothing voluntary in them.
3. Further, he that acts voluntarily, can act of himself. But this is not true of man; for it is written (Jn 15,5): "Without Me you can do nothing." Therefore there is nothing voluntary in human acts.

On the contrary Damascene says (De Fide Orth. ii) that "the voluntary is an act consisting in a rational operation." Now such are human acts. Therefore there is something voluntary in human acts.
I answer that There must needs be something voluntary in human acts. In order to make this clear, we must take note that the principle of some acts or movements is within the agent, or that which is moved; whereas the principle of some movements or acts is outside. For when a stone is moved upwards, the principle of this movement is outside the stone: whereas when it is moved downwards, the principle of this movement is in the stone. Now of those things that are moved by an intrinsic principle, some move themselves, some not. For since every agent or thing moved, acts or is moved for an end, as stated above (Question [1], Article [2]); those are perfectly moved by an intrinsic principle, whose intrinsic principle is one not only of movement but of movement for an end. Now in order for a thing to be done for an end, some knowledge of the end is necessary. Therefore, whatever so acts or is moved by an intrinsic principle, that it has some knowledge of the end, has within itself the principle of its act, so that it not only acts, but acts for an end. On the other hand, if a thing has no knowledge of the end, even though it have an intrinsic principle of action or movement, nevertheless the principle of acting or being moved for an end is not in that thing, but in something else, by which the principle of its action towards an end is not in that thing, but in something else, by which the principle of its action towards an end is imprinted on it. Wherefore such like things are not said to move themselves, but to be moved by others. But those things which have a knowledge of the end are said to move themselves because there is in them a principle by which they not only act but also act for an end. And consequently, since both are from an intrinsic principle, to wit, that they act and that they act for an end, the movements of such things are said to be voluntary: for the word "voluntary" implies that their movements and acts are from their own inclination. Hence it is that, according to the definitions of Aristotle, Gregory of Nyssa, and Damascene [*See Objection 1], the voluntary is defined not only as having "a principle within" the agent, but also as implying "knowledge." Therefore, since man especially knows the end of his work, and moves himself, in his acts especially is the voluntary to be found.

Reply to Objection: 1. Not every principle is a first principle. Therefore, although it is essential to the voluntary act that its principle be within the agent, nevertheless it is not contrary to the nature of the voluntary act that this intrinsic principle be caused or moved by an extrinsic principle: because it is not essential to the voluntary act that its intrinsic principle be a first principle. Yet again it must be observed that a principle of movement may happen to be first in a genus, but not first simply: thus in the genus of things subject to alteration, the first principle of alteration is a heavenly body, which is nevertheless, is not the first mover simply, but is moved locally by a higher mover. And so the intrinsic principle of the voluntary act, i.e. the cognitive and appetitive power, is the first principle in the genus of appetitive movement, although it is moved by an extrinsic principle according to other species of movement.
2. New movements in animals are indeed preceded by a motion from without; and this in two respects. First, in so far as by means of an extrinsic motion an animal's senses are confronted with something sensible, which, on being apprehended, moves the appetite. Thus a lion, on seeing a stag in movement and coming towards him, begins to be moved towards the stag. Secondly, in so far as some extrinsic motion produces a physical change in an animal's body, as in the case of cold or heat; and through the body being affected by the motion of an outward body, the sensitive appetite which is the power of a bodily organ, is also moved indirectly; thus it happens that through some alteration in the body the appetite is roused to the desire of something. But this is not contrary to the nature of voluntariness, as stated above (ad 1), for such movements caused by an extrinsic principle are of another genus of movement.
3. God moves man to act, not only by proposing the appetible to the senses, or by effecting a change in his body, but also by moving the will itself; because every movement either of the will or of nature, proceeds from God as the First Mover. And just as it is not incompatible with nature that the natural movement be from God as the First Mover, inasmuch as nature is an instrument of God moving it: so it is not contrary to the essence of a voluntary act, that it proceed from God, inasmuch as the will is moved by God. Nevertheless both natural and voluntary movements have this in common, that it is essential that they should proceed from a principle within the agent.

Whether there is anything voluntary in irrational animals?

Objection: 1. It would seem that there is nothing voluntary in irrational animals. For a thing is called "voluntary" from "voluntas" [will]. Now since the will is in the reason (De Anima iii, 9), it cannot be in irrational animals. Therefore neither is there anything voluntary in them.
2. Further, according as human acts are voluntary, man is said to be master of his actions. But irrational animals are not masters of their actions; for "they act not; rather are they acted upon," as Damascene says (De Fide Orth. ii, 27). Therefore there is no such thing as a voluntary act in irrational animals.
3. Further, Damascene says (De Fide Orth. 24) that "voluntary acts lead to praise and blame." But neither praise nor blame is due to the acts of irrational minds. Therefore such acts are not voluntary.

On the contrary The Philosopher says (Ethic. iii, 2) that "both children and irrational animals participate in the voluntary." The same is said by Damascene (De Fide Orth. 24) and Gregory of Nyssa [*Nemesius, De Nat. Hom. xxxii.].
I answer that As stated above (Article [1]), it is essential to the voluntary act that its principle be within the agent, together with some knowledge of the end. Now knowledge of the end is twofold; perfect and imperfect. Perfect knowledge of the end consists in not only apprehending the thing which is the end, but also in knowing it under the aspect of end, and the relationship of the means to that end. And such knowledge belongs to none but the rational nature. But imperfect knowledge of the end consists in mere apprehension of the end, without knowing it under the aspect of end, or the relationship of an act to the end. Such knowledge of the end is exercised by irrational animals, through their senses and their natural estimative power.Consequently perfect knowledge of the end leads to the perfect voluntary; inasmuch as, having apprehended the end, a man can, from deliberating about the end and the means thereto, be moved, or not, to gain that end. But imperfect knowledge of the end leads to the imperfect voluntary; inasmuch as the agent apprehends the end, but does not deliberate, and is moved to the end at once. Wherefore the voluntary in its perfection belongs to none but the rational nature: whereas the imperfect voluntary is within the competency of even irrational animals.

Reply to Objection: 1. The will is the name of the rational appetite; and consequently it cannot be in things devoid of reason. But the word "voluntary" is derived from "voluntas" [will], and can be extended to those things in which there is some participation of will, by way of likeness thereto. It is thus that voluntary action is attributed to irrational animals, in so far as they are moved to an end, through some kind of knowledge.
2. The fact that man is master of his actions, is due to his being able to deliberate about them: for since the deliberating reason is indifferently disposed to opposite things, the will can be inclined to either. But it is not thus that voluntariness is in irrational animals, as stated above.
3. Praise and blame are the result of the voluntary act, wherein is the perfect voluntary; such as is not to be found in irrational animals.

Summa Th. I-II EN Qu.5 a.4