Whether all the powers of the soul are in the soul as their subject?

Objection 1. It would seem that all the powers of the soul are in the soul as their subject. For as the powers of the body are to the body; so are the powers of the soul to the soul. But the body is the subject of the corporeal powers. Therefore the soul is the subject of the powers of the soul.

Objection 2. Further, the operations of the powers of the soul are attributed to the body by reason of the soul; because, as the Philosopher says (De Anima ii, 2), "The soul is that by which we sense and understand primarily." But the natural principles of the operations of the soul are the powers. Therefore the powers are primarily in the soul.

Objection 3. Further, Augustine says (Gen. ad lit. xii, 7,24) that the soul senses certain things, not through the body, in fact, without the body, as fear and such like; and some things through the body. But if the sensitive powers were not in the soul alone as their subject, the soul could not sense anything without the body. Therefore the soul is the subject of the sensitive powers; and for a similar reason, of all the other powers.

On the contrary, The Philosopher says (De Somno et Vigilia i) that "sensation belongs neither to the soul, nor to the body, but to the composite." Therefore the sensitive power is in "the composite" as its subject. Therefore the soul alone is not the subject of all the powers.

I answer that, The subject of operative power is that which is able to operate, for every accident denominates its proper subject. Now the same is that which is able to operate, and that which does operate. Wherefore the "subject of power" is of necessity "the subject of operation," as again the Philosopher says in the beginning of De Somno et Vigilia. Now, it is clear from what we have said above (I:75:3; I:76:1 ad 1), that some operations of the soul are performed without a corporeal organ, as understanding and will. Hence the powers of these operations are in the soul as their subject. But some operations of the soul are performed by means of corporeal organs; as sight by the eye, and hearing by the ear. And so it is with all the other operations of the nutritive and sensitive parts. Therefore the powers which are the principles of these operations have their subject in the composite, and not in the soul alone.

Reply to Objection 1. All the powers are said to belong to the soul, not as their subject, but as their principle; because it is by the soul that the composite has the power to perform such operations.

Reply to Objection 2. All such powers are primarily in the soul, as compared to the composite; not as in their subject, but as in their principle.

Reply to Objection 3. Plato's opinion was that sensation is an operation proper to the soul, just as understanding is. Now in many things relating to Philosophy Augustine makes use of the opinions of Plato, not asserting them as true, but relating them. However, as far as the present question is concerned, when it is said that the soul senses some things with the body, and some without the body, this can be taken in two ways.

Firstly, the words "with the body or without the body" may determine the act of sense in its mode of proceeding from the sentient. Thus the soul senses nothing without the body, because the action of sensation cannot proceed from the soul except by a corporeal organ.

Secondly, they may be understood as determining the act of sense on the part of the object sensed. Thus the soul senses some things with the body, that is, things existing in the body, as when it feels a wound or something of that sort; while it senses some things without the body, that is, which do not exist in the body, but only in the apprehension of the soul, as when it feels sad or joyful on hearing something.


Whether the powers of the soul flow from its essence?

Objection 1. It would seem that the powers of the soul do not flow from its essence. For different things do not proceed from one simple thing. But the essence of the soul is one and simple. Since, therefore, the powers of the soul are many and various, they cannot proceed from its essence.

Objection 2. Further, that from which a thing proceeds is its cause. But the essence of the soul cannot be said to be the cause of the powers; as is clear if one considers the different kinds of causes. Therefore the powers of the soul do not flow from its essence.

Objection 3. Further, emanation involves some sort of movement. But nothing is moved by itself, as the Philosopher proves (Phys. vii, 1,2); except, perhaps, by reason of a part of itself, as an animal is said to be moved by itself, because one part thereof moves and another is moved. Neither is the soul moved, as the Philosopher proves (De Anima i, 4). Therefore the soul does not produce its powers within itself.

On the contrary, The powers of the soul are its natural properties. But the subject is the cause of its proper accidents; whence also it is included in the definition of accident, as is clear from Metaph. vii (Did. vi, 4). Therefore the powers of the soul proceed from its essence as their cause.

I answer that, The substantial and the accidental form partly agree and partly differ. They agree in this, that each is an act; and that by each of them something is after a manner actual. They differ, however, in two respects.

First, because the substantial form makes a thing to exist absolutely, and its subject is something purely potential. But the accidental form does not make a thing to exist absolutely but to be such, or so great, or in some particular condition; for its subject is an actual being. Hence it is clear that actuality is observed in the substantial form prior to its being observed in the subject: and since that which is first in a genus is the cause in that genus, the substantial form causes existence in its subject. On the other hand, actuality is observed in the subject of the accidental form prior to its being observed in the accidental form; wherefore the actuality of the accidental form is caused by the actuality of the subject. So the subject, forasmuch as it is in potentiality, is receptive of the accidental form: but forasmuch as it is in act, it produces it. This I say of the proper and per se accident; for with regard to the extraneous accident, the subject is receptive only, the accident being caused by an extrinsic agent.

Secondly, substantial and accidental forms differ, because, since that which is the less principal exists for the sake of that which is the more principal, matter therefore exists on account of the substantial form; while on the contrary, the accidental form exists on account of the completeness of the subject.

Now it is clear, from what has been said (Article 5), that either the subject of the soul's powers is the soul itself alone, which can be the subject of an accident, forasmuch as it has something of potentiality, as we have said above (Article 1, Reply to Objection 6); or else this subject is the composite. Now the composite is actual by the soul. Whence it is clear that all the powers of the soul, whether their subject be the soul alone, or the composite, flow from the essence of the soul, as from their principle; because it has already been said that the accident is caused by the subject according as it is actual, and is received into it according as it is in potentiality.

Reply to Objection 1. From one simple thing many things may proceed naturally, in a certain order; or again if there be diversity of recipients. Thus, from the one essence of the soul many and various powers proceed; both because order exists among these powers; and also by reason of the diversity of the corporeal organs.

Reply to Objection 2. The subject is both the final cause, and in a way the active cause, of its proper accident. It is also as it were the material cause, inasmuch as it is receptive of the accident. From this we may gather that the essence of the soul is the cause of all its powers, as their end, and as their active principle; and of some as receptive thereof.

Reply to Objection 3. The emanation of proper accidents from their subject is not by way of transmutation, but by a certain natural resultance; thus one thing results naturally from another, as color from light.


Whether one power of the soul arises from another?

Objection 1. It would seem that one power of the soul does not arise from another. For if several things arise together, one of them does not arise from another. But all the powers of the soul are created at the same time with the soul. Therefore one of them does not arise from another.

Objection 2. Further, the power of the soul arises from the soul as an accident from the subject. But one power of the soul cannot be the subject of another; because nothing is the accident of an accident. Therefore one power does not arise from another.

Objection 3. Further, one opposite does not arise from the other opposite; but everything arises from that which is like it in species. Now the powers of the soul are oppositely divided, as various species. Therefore one of them does not proceed from another.

On the contrary, Powers are known by their actions. But the action of one power is caused by the action of another power, as the action of the imagination by the action of the senses. Therefore one power of the soul is caused by another.

I answer that, In those things which proceed from one according to a natural order, as the first is the cause of all, so that which is nearer to the first is, in a way, the cause of those which are more remote. Now it has been shown above (Article 4) that among the powers of the soul there are several kinds of order. Therefore one power of the soul proceeds from the essence of the soul by the medium of another. But since the essence of the soul is compared to the powers both as a principle active and final, and as a receptive principle, either separately by itself, or together with the body; and since the agent and the end are more perfect, while the receptive principle, as such, is less perfect; it follows that those powers of the soul which precede the others, in the order of perfection and nature, are the principles of the others, after the manner of the end and active principle. For we see that the senses are for the sake of the intelligence, and not the other way about. The senses, moreover, are a certain imperfect participation of the intelligence; wherefore, according to their natural origin, they proceed from the intelligence as the imperfect from the perfect. But considered as receptive principles, the more perfect powers are principles with regard to the others; thus the soul, according as it has the sensitive power, is considered as the subject, and as something material with regard to the intelligence. On this account, the more imperfect powers precede the others in the order of generation, for the animal is generated before the man.

Reply to Objection 1. As the power of the soul flows from the essence, not by a transmutation, but by a certain natural resultance, and is simultaneous with the soul, so is it the case with one power as regards another.

Reply to Objection 2. An accident cannot of itself be the subject of an accident; but one accident is received prior to another into substance, as quantity prior to quality. In this sense one accident is said to be the subject of another; as surface is of color, inasmuch as substance receives an accident through the means of another. The same thing may be said of the powers of the soul.

Reply to Objection 3. The powers of the soul are opposed to one another, as perfect and imperfect; as also are the species of numbers and figures. But this opposition does not prevent the origin of one from another, because imperfect things naturally proceed from perfect things.


Whether all the powers remain in the soul when separated from the body?

Objection 1. It would seem that all the powers of the soul remain in the soul separated from the body. For we read in the book De Spiritu et Anima that "the soul withdraws from the body, taking with itself sense and imagination, reason and intelligence, concupiscibility and irascibility."

Objection 2. Further, the powers of the soul are its natural properties. But properties are always in that to which they belong; and are never separated from it. Therefore the powers of the soul are in it even after death.

Objection 3. Further, the powers even of the sensitive soul are not weakened when the body becomes weak; because, as the Philosopher says (De Anima i, 4), "If an old man were given the eye of a young man, he would see even as well as a young man." But weakness is the road to corruption. Therefore the powers of the soul are not corrupted when the body is corrupted, but remain in the separated soul.

Objection 4. Further, memory is a power of the sensitive soul, as the Philosopher proves (De Memor. et Remin. 1). But memory remains in the separated soul; for it was said to the rich glutton whose soul was in hell: "Remember that thou didst receive good things during thy lifetime" (Luke 16:25). Therefore memory remains in the separated soul; and consequently the other powers of the sensitive part.

Objection 5. Further, joy and sorrow are in the concupiscible part, which is a power of the sensitive soul. But it is clear that separate souls grieve or rejoice at the pains or rewards which they receive. Therefore the concupiscible power remains in the separate soul.

Objection 6. Further, Augustine says (Gen. ad lit. xii, 32) that, as the soul, when the body lies senseless, yet not quite dead, sees some things by imaginary vision; so also when by death the soul is quite separate from the body. But the imagination is a power of the sensitive part. Therefore the power of the sensitive part remains in the separate soul; and consequently all the other powers.

On the contrary, It is said (De Eccl. Dogm. xix) that "of two substances only does man consist; the soul with its reason, and the body with its senses." Therefore the body being dead, the sensitive powers do not remain.

I answer that, As we have said already (Articles 5, 6, and 7), all the powers of the soul belong to the soul alone as their principle. But some powers belong to the soul alone as their subject; as the intelligence and the will. These powers must remain in the soul, after the destruction of the body. But other powers are subjected in the composite; as all the powers of the sensitive and nutritive parts. Now accidents cannot remain after the destruction of the subject. Wherefore, the composite being destroyed, such powers do not remain actually; but they remain virtually in the soul, as in their principle or root.

So it is false that, as some say, these powers remain in the soul even after the corruption of the body. It is much more false that, as they say also, the acts of these powers remain in the separate soul; because these powers have no act apart from the corporeal organ.

Reply to Objection 1. That book has no authority, and so what is there written can be despised with the same facility as it was said; although we may say that the soul takes with itself these powers, not actually but virtually.

Reply to Objection 2. These powers, which we say do not actually remain in the separate soul, are not the properties of the soul alone, but of the composite.

Reply to Objection 3. These powers are said not to be weakened when the body becomes weak, because the soul remains unchangeable, and is the virtual principle of these powers.

Reply to Objection 4. The recollection spoken of there is to be taken in the same way as Augustine (De Trin. x, 11; xiv, 7) places memory in the mind; not as a part of the sensitive soul.

Reply to Objection 5. In the separate soul, sorrow and joy are not in the sensitive, but in the intellectual appetite, as in the angels.

Reply to Objection 6. Augustine in that passage is speaking as inquiring, not as asserting. Wherefore he retracted some things which he had said there (Retrac. ii, 24).

The Summa Theologiæ of St. Thomas AquinasSecond and Revised Edition, 1920Literally translated by Fathers of the English Dominican ProvinceOnline Edition Copyright © 2017 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

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Whether there are to be distinguished five genera of powers in the soul?

Objection 1. It would seem that there are not to be distinguished five genera of powers in the soul—namely, vegetative, sensitive, appetitive, locomotive, and intellectual. For the powers of the soul are called its parts. But only three parts of the soul are commonly assigned—namely, the vegetative soul, the sensitive soul, and the rational soul. Therefore there are only three genera of powers in the soul, and not five.

Objection 2. Further, the powers of the soul are the principles of its vital operations. Now, in four ways is a thing said to live. For the Philosopher says (De Anima ii, 2): "In several ways a thing is said to live, and even if only one of these is present, the thing is said to live; as intellect and sense, local movement and rest, and lastly, movement of decrease and increase due to nourishment." Therefore there are only four genera of powers of the soul, as the appetitive is excluded.

Objection 3. Further, a special kind of soul ought not to be assigned as regards what is common to all the powers. Now desire is common to each power of the soul. For sight desires an appropriate visible object; whence we read (Sirach 40:22): "The eye desireth favor and beauty, but more than these green sown fields." In the same way every other power desires its appropriate object. Therefore the appetitive power should not be made a special genus of the powers of the soul.

Objection 4. Further, the moving principle in animals is sense, intellect or appetite, as the Philosopher says (De Anima iii, 10). Therefore the motive power should not be added to the above as a special genus of soul.

On the contrary, The Philosopher says (De Anima ii, 3), "The powers are the vegetative, the sensitive, the appetitive, the locomotion, and the intellectual."

I answer that, There are five genera of powers of the soul, as above numbered. Of these, three are called souls, and four are called modes of living. The reason of this diversity lies in the various souls being distinguished accordingly as the operation of the soul transcends the operation of the corporeal nature in various ways; for the whole corporeal nature is subject to the soul, and is related to it as its matter and instrument. There exists, therefore, an operation of the soul which so far exceeds the corporeal nature that it is not even performed by any corporeal organ; and such is the operation of the "rational soul." Below this, there is another operation of the soul, which is indeed performed through a corporeal organ, but not through a corporeal quality, and this is the operation of the "sensitive soul"; for though hot and cold, wet and dry, and other such corporeal qualities are required for the work of the senses, yet they are not required in such a way that the operation of the senses takes place by virtue of such qualities; but only for the proper disposition of the organ. The lowest of the operations of the soul is that which is performed by a corporeal organ, and by virtue of a corporeal quality. Yet this transcends the operation of the corporeal nature; because the movements of bodies are caused by an extrinsic principle, while these operations are from an intrinsic principle; for this is common to all the operations of the soul; since every animate thing, in some way, moves itself. Such is the operation of the "vegetative soul"; for digestion, and what follows, is caused instrumentally by the action of heat, as the Philosopher says (De Anima ii, 4).

Now the powers of the soul are distinguished generically by their objects. For the higher a power is, the more universal is the object to which it extends, as we have said above (I:77:3 ad 4). But the object of the soul's operation may be considered in a triple order. For in the soul there is a power the object of which is only the body that is united to that soul; the powers of this genus are called "vegetative" for the vegetative power acts only on the body to which the soul is united. There is another genus in the powers of the soul, which genus regards a more universal object—namely, every sensible body, not only the body to which the soul is united. And there is yet another genus in the powers of the soul, which genus regards a still more universal object—namely, not only the sensible body, but all being in universal. Wherefore it is evident that the latter two genera of the soul's powers have an operation in regard not merely to that which is united to them, but also to something extrinsic. Now, since whatever operates must in some way be united to the object about which it operates, it follows of necessity that this something extrinsic, which is the object of the soul's operation, must be related to the soul in a twofold manner.

First, inasmuch as this something extrinsic has a natural aptitude to be united to the soul, and to be by its likeness in the soul. In this way there are two kinds of powers —namely, the "sensitive" in regard to the less common object—the sensible body; and the "intellectual," in regard to the most common object—universal being.

Secondly, forasmuch as the soul itself has an inclination and tendency to the something extrinsic. And in this way there are again two kinds of powers in the soul: one—the "appetitive"—in respect of which the soul is referred to something extrinsic as to an end, which is first in the intention; the other—the "locomotive" power—in respect of which the soul is referred to something extrinsic as to the term of its operation and movement; for every animal is moved for the purpose of realizing its desires and intentions.

The modes of living are distinguished according to the degrees of living things. There are some living things in which there exists only vegetative power, as the plants. There are others in which with the vegetative there exists also the sensitive, but not the locomotive power; such as immovable animals, as shellfish. There are others which besides this have locomotive powers, as perfect animals, which require many things for their life, and consequently movement to seek necessaries of life from a distance. And there are some living things which with these have intellectual power—namely, men. But the appetitive power does not constitute a degree of living things; because wherever there is sense there is also appetite (De Anima ii, 3).

Thus the first two objectives are hereby solved.

Reply to Objection 3. The "natural appetite" is that inclination which each thing has, of its own nature, for something; wherefore by its natural appetite each power desires something suitable to itself. But the "animal appetite" results from the form apprehended; this sort of appetite requires a special power of the soul—mere apprehension does not suffice. For a thing is desired as it exists in its own nature, whereas in the apprehensive power it exists not according to its own nature, but according to its likeness. Whence it is clear that sight desires naturally a visible object for the purpose of its act only—namely, for the purpose of seeing; but the animal by the appetitive power desires the thing seen, not merely for the purpose of seeing it, but also for other purposes. But if the soul did not require things perceived by the senses, except on account of the actions of the senses, that is, for the purpose of sensing them; there would be no need for a special genus of appetitive powers, since the natural appetite of the powers would suffice.

Reply to Objection 4. Although sense and appetite are principles of movement in perfect animals, yet sense and appetite, as such, are not sufficient to cause movement, unless another power be added to them; for immovable animals have sense and appetite, and yet they have not the power of motion. Now this motive power is not only in the appetite and sense as commanding the movement, but also in the parts of the body, to make them obey the appetite of the soul which moves them. Of this we have a sign in the fact that when the members are deprived of their natural disposition, they do not move in obedience to the appetite.


Whether the parts of the vegetative soul are fittingly described as the nutritive, augmentative, and generative?

Objection 1. It would seem that the parts of the vegetative soul are not fittingly described—namely, the nutritive, augmentative, and generative. For these are called "natural" forces. But the powers of the soul are above the natural forces. Therefore we should not class the above forces as powers of the soul.

Objection 2. Further, we should not assign a particular power of the soul to that which is common to living and non-living things. But generation is common to all things that can be generated and corrupted, whether living or not living. Therefore the generative force should not be classed as a power of the soul.

Objection 3. Further, the soul is more powerful than the body. But the body by the same force gives species and quantity; much more, therefore, does the soul. Therefore the augmentative power of the soul is not distinct from the generative power.

Objection 4. Further, everything is preserved in being by that whereby it exists. But the generative power is that whereby a living thing exists. Therefore by the same power the living thing is preserved. Now the nutritive force is directed to the preservation of the living thing (De Anima ii, 4), being "a power which is capable of preserving whatever receives it." Therefore we should not distinguish the nutritive power from the generative.

On the contrary, The Philosopher says (De Anima ii, 2,4) that the operations of this soul are "generation, the use of food," and (cf. De Anima iii, 9) "growth."

I answer that, The vegetative part has three powers. For the vegetative part, as we have said (Article 1), has for its object the body itself, living by the soul; for which body a triple operation of the soul is required. One is whereby it acquires existence, and to this is directed the "generative" power. Another is whereby the living body acquires its due quantity; to this is directed the "augmentative" power. Another is whereby the body of a living thing is preserved in its existence and in its due quantity; to this is directed the "nutritive" power.

We must, however, observe a difference among these powers. The nutritive and the augmentative have their effect where they exist, since the body itself united to the soul grows and is preserved by the augmentative and nutritive powers which exist in one and the same soul. But the generative power has its effect, not in one and the same body but in another; for a thing cannot generate itself. Therefore the generative power, in a way, approaches to the dignity of the sensitive soul, which has an operation extending to extrinsic things, although in a more excellent and more universal manner; for that which is highest in an inferior nature approaches to that which is lowest in the higher nature, as is made clear by Dionysius (Div. Nom. vii). Therefore, of these three powers, the generative has the greater finality, nobility, and perfection, as the Philosopher says (De Anima ii, 4), for it belongs to a thing which is already perfect to "produce another like unto itself." And the generative power is served by the augmentative and nutritive powers; and the augmentative power by the nutritive.

Reply to Objection 1. Such forces are called natural, both because they produce an effect like that of nature, which also gives existence, quantity and preservation (although the above forces accomplish these things in a more perfect way); and because those forces perform their actions instrumentally, through the active and passive qualities, which are the principles of natural actions.

Reply to Objection 2. Generation of inanimate things is entirely from an extrinsic source; whereas the generation of living things is in a higher way, through something in the living thing itself, which is the semen containing the principle productive of the body. Therefore there must be in the living thing a power that prepares this semen; and this is the generative power.

Reply to Objection 3. Since the generation of living things is from a semen, it is necessary that in the beginning an animal of small size be generated. For this reason it must have a power in the soul, whereby it is brought to its appropriate size. But the inanimate body is generated from determinate matter by an extrinsic agent; therefore it receives at once its nature and its quantity, according to the condition of the matter.

Reply to Objection 4. As we have said above (Article 1), the operation of the vegetative principle is performed by means of heat, the property of which is to consume humidity. Therefore, in order to restore the humidity thus lost, the nutritive power is required, whereby the food is changed into the substance of the body. This is also necessary for the action of the augmentative and generative powers.


Whether the five exterior senses are properly distinguished?

Objection 1. It would seem inaccurate to distinguish five exterior senses. But there are many kinds of accidents. Therefore, as powers are distinguished by their objects, it seems that the senses are multiplied according to the number of the kinds of accidents.

Objection 2. Further, magnitude and shape, and other things which are called "common sensibles," are "not sensibles by accident," but are contradistinguished from them by the Philosopher (De Anima ii, 6). Now the diversity of objects, as such, diversifies the powers. Since, therefore, magnitude and shape are further from color than sound is, it seems that there is much more need for another sensitive power than can grasp magnitude or shape than for that which grasps color or sound.

Objection 3. Further, one sense regards one contrariety; as sight regards white and black. But the sense of touch grasps several contraries; such as hot or cold, damp or dry, and suchlike. Therefore it is not a single sense but several. Therefore there are more than five senses.

Objection 4. Further, a species is not divided against its genus. But taste is a kind of touch. Therefore it should not be classed as a distinct sense of touch.

On the contrary, The Philosopher says (De Anima iii, 1): "There is no other besides the five senses."

I answer that, The reason of the distinction and number of the senses has been assigned by some to the organs in which one or other of the elements preponderate, as water, air, or the like. By others it has been assigned to the medium, which is either in conjunction or extrinsic and is either water or air, or such like. Others have ascribed it to the various natures of the sensible qualities, according as such quality belongs to a simple body or results from complexity. But none of these explanations is apt. For the powers are not for the organs, but the organs for the powers; wherefore there are not various powers for the reason that there are various organs; on the contrary, for this has nature provided a variety of organs, that they might be adapted to various powers. In the same way nature provided various mediums for the various senses, according to the convenience of the acts of the powers. And to be cognizant of the natures of sensible qualities does not pertain to the senses, but to the intellect.

The reason of the number and distinction of the exterior senses must therefore be ascribed to that which belongs to the senses properly and "per se." Now, sense is a passive power, and is naturally immuted by the exterior sensible. Wherefore the exterior cause of such immutation is what is per se perceived by the sense, and according to the diversity of that exterior cause are the sensitive powers diversified.

Now, immutation is of two kinds, one natural, the other spiritual. Natural immutation takes place by the form of the immuter being received according to its natural existence, into the thing immuted, as heat is received into the thing heated. Whereas spiritual immutation takes place by the form of the immuter being received, according to a spiritual mode of existence, into the thing immuted, as the form of color is received into the pupil which does not thereby become colored. Now, for the operation of the senses, a spiritual immutation is required, whereby an intention of the sensible form is effected in the sensile organ. Otherwise, if a natural immutation alone sufficed for the sense's action, all natural bodies would feel when they undergo alteration.

But in some senses we find spiritual immutation only, as in "sight" while in others we find not only spiritual but also a natural immutation; either on the part of the object only, or likewise on the part of the organ. On the part of the object we find natural immutation, as to place, in sound which is the object of "hearing"; for sound is caused by percussion and commotion of air: and we find natural immutation by alteration, in odor which is the object of "smelling"; for in order to exhale an odor, a body must be in a measure affected by heat. On the part of an organ, natural immutation takes place in "touch" and "taste"; for the hand that touches something hot becomes hot, while the tongue is moistened by the humidity of the flavored morsel. But the organs of smelling and hearing are not affected in their respective operations by any natural immutation unless indirectly.

Now, the sight, which is without natural immutation either in its organ or in its object, is the most spiritual, the most perfect, and the most universal of all the senses. After this comes the hearing and then the smell, which require a natural immutation on the part of the object; while local motion is more perfect than, and naturally prior to, the motion of alteration, as the Philosopher proves (Phys. viii, 7). Touch and taste are the most material of all: of the distinction of which we shall speak later on (Replies to Objections 3 and 4). Hence it is that the three other senses are not exercised through a medium united to them, to obviate any natural immutation in their organ; as happens as regards these two senses.

Reply to Objection 1. Not every accident has in itself a power of immutation but only qualities of the third species, which are the principles of alteration: therefore only suchlike qualities are the objects of the senses; because "the senses are affected by the same things whereby inanimate bodies are affected," as stated in Phys. vii, 2.

Reply to Objection 2. Size, shape, and the like, which are called "common sensibles," are midway between "accidental sensibles" and "proper sensibles," which are the objects of the senses. For the proper sensibles first, and of their very nature, affect the senses; since they are qualities that cause alteration. But the common sensibles are all reducible to quantity. As to size and number, it is clear that they are species of quantity. Shape is a quality about quantity. Shape is a quality about quantity, since the notion of shape consists of fixing the bounds of magnitude. Movement and rest are sensed according as the subject is affected in one or more ways in the magnitude of the subject or of its local distance, as in the movement of growth or of locomotion, or again, according as it is affected in some sensible qualities, as in the movement of alteration; and thus to sense movement and rest is, in a way, to sense one thing and many. Now quantity is the proximate subject of the qualities that cause alteration, as surface is of color. Therefore the common sensibles do not move the senses first and of their own nature, but by reason of the sensible quality; as the surface by reason of color. Yet they are not accidental sensibles, for they produce a certain variety in the immutation of the senses. For sense is immuted differently by a large and by a small surface: since whiteness itself is said to be great or small, and therefore it is divided according to its proper subject.

Reply to Objection 3. As the Philosopher seems to say (De Anima ii, 11), the sense of touch is generically one, but is divided into several specific senses, and for this reason it extends to various contrarieties; which senses, however, are not separate from one another in their organ, but are spread throughout the whole body, so that their distinction is not evident. But taste, which perceives the sweet and the bitter, accompanies touch in the tongue, but not in the whole body; so it is easily distinguished from touch. We might also say that all those contrarieties agree, each in some proximate genus, and all in a common genus, which is the common and formal object of touch. Such common genus is, however, unnamed, just as the proximate genus of hot and cold is unnamed.

Reply to Objection 4. The sense of taste, according to a saying of the Philosopher (De Anima ii, 9), is a kind of touch existing in the tongue only. It is not distinct from touch in general, but only from the species of touch distributed in the body. But if touch is one sense only, on account of the common formality of its object: we must say that taste is distinguished from touch by reason of a different formality of immutation. For touch involves a natural, and not only a spiritual, immutation in its organ, by reason of the quality which is its proper object. But the organ of taste is not necessarily immuted by a natural immutation by reason of the quality which is its proper object, so that the tongue itself becomes sweet and bitter: but by reason of a quality which is a preamble to, and on which is based, the flavor, which quality is moisture, the object of touch.


Whether the interior senses are suitably distinguished?

Objection 1. It would seem that the interior senses are not suitably distinguished. For the common is not divided against the proper. Therefore the common sense should not be numbered among the interior sensitive powers, in addition to the proper exterior senses.

Objection 2. Further, there is no need to assign an interior power of apprehension when the proper and exterior sense suffices. But the proper and exterior senses suffice for us to judge of sensible things; for each sense judges of its proper object. In like manner they seem to suffice for the perception of their own actions; for since the action of the sense is, in a way, between the power and its object, it seems that sight must be much more able to perceive its own vision, as being nearer to it, than the color; and in like manner with the other senses. Therefore for this there is no need to assign an interior power, called the common sense.

Objection 3. Further, according to the Philosopher (De Memor. et Remin. i), the imagination and the memory are passions of the "first sensitive." But passion is not divided against its subject. Therefore memory and imagination should not be assigned as powers distinct from the senses.

Objection 4. Further, the intellect depends on the senses less than any power of the sensitive part. But the intellect knows nothing but what it receives from the senses; whence we read (Poster. i, 8), that "those who lack one sense lack one kind of knowledge." Therefore much less should we assign to the sensitive part a power, which they call the "estimative" power, for the perception of intentions which the sense does not perceive.

Objection 5. Further, the action of the cogitative power, which consists in comparing, adding and dividing, and the action of the reminiscence, which consists in the use of a kind of syllogism for the sake of inquiry, is not less distant from the actions of the estimative and memorative powers, than the action of the estimative is from the action of the imagination. Therefore either we must add the cognitive and reminiscitive to the estimative and memorative powers, or the estimative and memorative powers should not be made distinct from the imagination.

Objection 6. Further, Augustine (Gen. ad lit. xii, 6,7,24) describes three kinds of vision; namely, corporeal, which is the action of the sense; spiritual, which is an action of the imagination or phantasy; and intellectual, which is an action of the intellect. Therefore there is no interior power between the sense and intellect, besides the imagination.

On the contrary, Avicenna (De Anima iv, 1) assigns five interior sensitive powers; namely, "common sense, phantasy, imagination, and the estimative and memorative powers."

I answer that, As nature does not fail in necessary things, there must needs be as many actions of the sensitive soul as may suffice for the life of a perfect animal. If any of these actions cannot be reduced to the same one principle, they must be assigned to diverse powers; since a power of the soul is nothing else than the proximate principle of the soul's operation.

Now we must observe that for the life of a perfect animal, the animal should apprehend a thing not only at the actual time of sensation, but also when it is absent. Otherwise, since animal motion and action follow apprehension, an animal would not be moved to seek something absent: the contrary of which we may observe specially in perfect animals, which are moved by progression, for they are moved towards something apprehended and absent. Therefore an animal through the sensitive soul must not only receive the species of sensible things, when it is actually affected by them, but it must also retain and preserve them. Now to receive and retain are, in corporeal things, reduced to diverse principles; for moist things are apt to receive, but retain with difficulty, while it is the reverse with dry things. Wherefore, since the sensitive power is the act of a corporeal organ, it follows that the power which receives the species of sensible things must be distinct from the power which preserves them.

Again we must observe that if an animal were moved by pleasing and disagreeable things only as affecting the sense, there would be no need to suppose that an animal has a power besides the apprehension of those forms which the senses perceive, and in which the animal takes pleasure, or from which it shrinks with horror. But the animal needs to seek or to avoid certain things, not only because they are pleasing or otherwise to the senses, but also on account of other advantages and uses, or disadvantages: just as the sheep runs away when it sees a wolf, not on account of its color or shape, but as a natural enemy: and again a bird gathers together straws, not because they are pleasant to the sense, but because they are useful for building its nest. Animals, therefore, need to perceive such intentions, which the exterior sense does not perceive. And some distinct principle is necessary for this; since the perception of sensible forms comes by an immutation caused by the sensible, which is not the case with the perception of those intentions.

Thus, therefore, for the reception of sensible forms, the "proper sense" and the "common sense" are appointed, and of their distinction we shall speak farther on (Replies to Objections 1 and 2). But for the retention and preservation of these forms, the "phantasy" or "imagination" is appointed; which are the same, for phantasy or imagination is as it were a storehouse of forms received through the senses. Furthermore, for the apprehension of intentions which are not received through the senses, the "estimative" power is appointed: and for the preservation thereof, the "memorative" power, which is a storehouse of such-like intentions. A sign of which we have in the fact that the principle of memory in animals is found in some such intention, for instance, that something is harmful or otherwise. And the very formality of the past, which memory observes, is to be reckoned among these intentions.

Now, we must observe that as to sensible forms there is no difference between man and other animals; for they are similarly immuted by the extrinsic sensible. But there is a difference as to the above intentions: for other animals perceive these intentions only by some natural instinct, while man perceives them by means of coalition of ideas. Therefore the power by which in other animals is called the natural estimative, in man is called the "cogitative," which by some sort of collation discovers these intentions. Wherefore it is also called the "particular reason," to which medical men assign a certain particular organ, namely, the middle part of the head: for it compares individual intentions, just as the intellectual reason compares universal intentions. As to the memorative power, man has not only memory, as other animals have in the sudden recollection of the past; but also "reminiscence" by syllogistically, as it were, seeking for a recollection of the past by the application of individual intentions. Avicenna, however, assigns between the estimative and the imaginative, a fifth power, which combines and divides imaginary forms: as when from the imaginary form of gold, and imaginary form of a mountain, we compose the one form of a golden mountain, which we have never seen. But this operation is not to be found in animals other than man, in whom the imaginative power suffices thereto. To man also does Averroes attribute this action in his book De sensu et sensibilibus (viii). So there is no need to assign more than four interior powers of the sensitive part—namely, the common sense, the imagination, and the estimative and memorative powers.

Reply to Objection 1. The interior sense is called "common" not by predication, as if it were a genus; but as the common root and principle of the exterior senses.

Reply to Objection 2. The proper sense judges of the proper sensible by discerning it from other things which come under the same sense; for instance, by discerning white from black or green. But neither sight nor taste can discern white from sweet: because what discerns between two things must know both. Wherefore the discerning judgment must be assigned to the common sense; to which, as to a common term, all apprehensions of the senses must be referred: and by which, again, all the intentions of the senses are perceived; as when someone sees that he sees. For this cannot be done by the proper sense, which only knows the form of the sensible by which it is immuted, in which immutation the action of sight is completed, and from immutation follows another in the common sense which perceives the act of vision.

Reply to Objection 3. As one power arises from the soul by means of another, as we have seen above (I:77:7), so also the soul is the subject of one power through another. In this way the imagination and the memory are called passions of the "first sensitive."

Reply to Objection 4. Although the operation of the intellect has its origin in the senses: yet, in the thing apprehended through the senses, the intellect knows many things which the senses cannot perceive. In like manner does the estimative power, though in a less perfect manner.

Reply to Objection 5. The cogitative and memorative powers in man owe their excellence not to that which is proper to the sensitive part; but to a certain affinity and proximity to the universal reason, which, so to speak, overflows into them. Therefore they are not distinct powers, but the same, yet more perfect than in other animals.

Reply to Objection 6. Augustine calls that vision spiritual which is effected by the images of bodies in the absence of bodies. Whence it is clear that it is common to all interior apprehensions.

The Summa Theologiæ of St. Thomas AquinasSecond and Revised Edition, 1920Literally translated by Fathers of the English Dominican ProvinceOnline Edition Copyright © 2017 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

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Whether the intellect is a power of the soul?

Objection 1. It would seem that the intellect is not a power of the soul, but the essence of the soul. For the intellect seems to be the same as the mind. Now the mind is not a power of the soul, but the essence; for Augustine says (De Trin. ix, 2): "Mind and spirit are not relative things, but denominate the essence." Therefore the intellect is the essence of the soul.

Objection 2. Further, different genera of the soul's powers are not united in some one power, but only in the essence of the soul. Now the appetitive and the intellectual are different genera of the soul's powers as the Philosopher says (De Anima ii, 3), but they are united in the mind, for Augustine (De Trin. x, 11) places the intelligence and will in the mind. Therefore the mind and intellect of man is of the very essence of the soul and not a power thereof.

Objection 3. Further, according to Gregory, in a homily for the Ascension (xxix in Ev.), "man understands with the angels." But angels are called "minds" and "intellects." Therefore the mind and intellect of man are not a power of the soul, but the soul itself.

Objection 4. Further, a substance is intellectual by the fact that it is immaterial. But the soul is immaterial through its essence. Therefore it seems that the soul must be intellectual through its essence.

On the contrary, The Philosopher assigns the intellectual faculty as a power of the soul (De Anima ii, 3).

I answer that, In accordance with what has been already shown (I:54:3; I:77:1) it is necessary to say that the intellect is a power of the soul, and not the very essence of the soul. For then alone the essence of that which operates is the immediate principle of operation, when operation itself is its being: for as power is to operation as its act, so is the essence to being. But in God alone His action of understanding is His very Being. Wherefore in God alone is His intellect His essence: while in other intellectual creatures, the intellect is power.

Reply to Objection 1. Sense is sometimes taken for the power, and sometimes for the sensitive soul; for the sensitive soul takes its name from its chief power, which is sense. And in like manner the intellectual soul is sometimes called intellect, as from its chief power; and thus we read (De Anima i, 4), that the "intellect is a substance." And in this sense also Augustine says that the mind is spirit and essence (De Trin. ix, 2; xiv, 16).

Reply to Objection 2. The appetitive and intellectual powers are different genera of powers in the soul, by reason of the different formalities of their objects. But the appetitive power agrees partly with the intellectual power and partly with the sensitive in its mode of operation either through a corporeal organ or without it: for appetite follows apprehension. And in this way Augustine puts the will in the mind; and the Philosopher, in the reason (De Anima iii, 9).

Reply to Objection 3. In the angels there is no other power besides the intellect, and the will, which follows the intellect. And for this reason an angel is called a "mind" or an "intellect"; because his whole power consists in this. But the soul has many other powers, such as the sensitive and nutritive powers, and therefore the comparison fails.

Reply to Objection 4. The immateriality of the created intelligent substance is not its intellect; and through its immateriality it has the power of intelligence. Wherefore it follows not that the intellect is the substance of the soul, but that it is its virtue and power.


Whether the intellect is a passive power?

Objection 1. It would seem that the intellect is not a passive power. For everything is passive by its matter, and acts by its form. But the intellectual power results from the immateriality of the intelligent substance. Therefore it seems that the intellect is not a passive power.

Objection 2. Further, the intellectual power is incorruptible, as we have said above (I:79:6). But "if the intellect is passive, it is corruptible" (De Anima iii, 5). Therefore the intellectual power is not passive.

Objection 3. Further, the "agent is nobler than the patient," as Augustine (Gen. ad lit. xii, 16) and Aristotle (De Anima iii, 5) says. But all the powers of the vegetative part are active; yet they are the lowest among the powers of the soul. Much more, therefore, all the intellectual powers, which are the highest, are active.

On the contrary, The Philosopher says (De Anima iii, 4) that "to understand is in a way to be passive."

I answer that, To be passive may be taken in three ways.

Firstly, in its most strict sense, when from a thing is taken something which belongs to it by virtue either of its nature, or of its proper inclination: as when water loses coolness by heating, and as when a man becomes ill or sad.

Secondly, less strictly, a thing is said to be passive, when something, whether suitable or unsuitable, is taken away from it. And in this way not only he who is ill is said to be passive, but also he who is healed; not only he that is sad, but also he that is joyful; or whatever way he be altered or moved.

Thirdly, in a wide sense a thing is said to be passive, from the very fact that what is in potentiality to something receives that to which it was in potentiality, without being deprived of anything. And accordingly, whatever passes from potentiality to act, may be said to be passive, even when it is perfected. And thus with us to understand is to be passive. This is clear from the following reason. For the intellect, as we have seen above (I:78:1), has an operation extending to universal being. We may therefore see whether the intellect be in act or potentiality by observing first of all the nature of the relation of the intellect to universal being. For we find an intellect whose relation to universal being is that of the act of all being: and such is the Divine intellect, which is the Essence of God, in which originally and virtually, all being pre-exists as in its first cause. And therefore the Divine intellect is not in potentiality, but is pure act. But no created intellect can be an act in relation to the whole universal being; otherwise it would needs be an infinite being. Wherefore every created intellect is not the act of all things intelligible, by reason of its very existence; but is compared to these intelligible things as a potentiality to act.

Now, potentiality has a double relation to act. There is a potentiality which is always perfected by its act: as the matter of the heavenly bodies (I:58:1. And there is another potentiality which is not always in act, but proceeds from potentiality to act; as we observe in things that are corrupted and generated. Wherefore the angelic intellect is always in act as regards those things which it can understand, by reason of its proximity to the first intellect, which is pure act, as we have said above. But the human intellect, which is the lowest in the order of intelligence and most remote from the perfection of the Divine intellect, is in potentiality with regard to things intelligible, and is at first "like a clean tablet on which nothing is written," as the Philosopher says (De Anima iii, 4). This is made clear from the fact, that at first we are only in potentiality to understand, and afterwards we are made to understand actually. And so it is evident that with us to understand is "in a way to be passive"; taking passion in the third sense. And consequently the intellect is a passive power.

Reply to Objection 1. This objection is verified of passion in the first and second senses, which belong to primary matter. But in the third sense passion is in anything which is reduced from potentiality to act.

Reply to Objection 2. "Passive intellect" is the name given by some to the sensitive appetite, in which are the passions of the soul; which appetite is also called "rational by participation," because it "obeys the reason" (Ethic. i, 13). Others give the name of passive intellect to the cogitative power, which is called the "particular reason." And in each case "passive" may be taken in the two first senses; forasmuch as this so-called intellect is the act of a corporeal organ. But the intellect which is in potentiality to things intelligible, and which for this reason Aristotle calls the "possible" intellect (De Anima iii, 4) is not passive except in the third sense: for it is not an act of a corporeal organ. Hence it is incorruptible.

Reply to Objection 3. The agent is nobler than the patient, if the action and the passion are referred to the same thing: but not always, if they refer to different things. Now the intellect is a passive power in regard to the whole universal being: while the vegetative power is active in regard to some particular thing, namely, the body as united to the soul. Wherefore nothing prevents such a passive force being nobler than such an active one.


Whether there is an active intellect?

Objection 1. It would seem that there is no active intellect. For as the senses are to things sensible, so is our intellect to things intelligible. But because sense is in potentiality to things sensible, the sense is not said to be active, but only passive. Therefore, since our intellect is in potentiality to things intelligible, it seems that we cannot say that the intellect is active, but only that it is passive.

Objection 2. Further, if we say that also in the senses there is something active, such as light: on the contrary, light is required for sight, inasmuch as it makes the medium to be actually luminous; for color of its own nature moves the luminous medium. But in the operation of the intellect there is no appointed medium that has to be brought into act. Therefore there is no necessity for an active intellect.

Objection 3. Further, the likeness of the agent is received into the patient according to the nature of the patient. But the passive intellect is an immaterial power. Therefore its immaterial nature suffices for forms to be received into it immaterially. Now a form is intelligible in act from the very fact that it is immaterial. Therefore there is no need for an active intellect to make the species actually intelligible.

On the contrary, The Philosopher says (De Anima iii, 5), "As in every nature, so in the soul is there something by which it becomes all things, and something by which it makes all things." Therefore we must admit an active intellect.

I answer that, According to the opinion of Plato, there is no need for an active intellect in order to make things actually intelligible; but perhaps in order to provide intellectual light to the intellect, as will be explained farther on (Article 4). For Plato supposed that the forms of natural things subsisted apart from matter, and consequently that they are intelligible: since a thing is actually intelligible from the very fact that it is immaterial. And he called such forms "species or ideas"; from a participation of which, he said that even corporeal matter was formed, in order that individuals might be naturally established in their proper genera and species: and that our intellect was formed by such participation in order to have knowledge of the genera and species of things. But since Aristotle did not allow that forms of natural things exist apart from matter, and as forms existing in matter are not actually intelligible; it follows that the natures of forms of the sensible things which we understand are not actually intelligible. Now nothing is reduced from potentiality to act except by something in act; as the senses as made actual by what is actually sensible. We must therefore assign on the part of the intellect some power to make things actually intelligible, by abstraction of the species from material conditions. And such is the necessity for an active intellect.

Reply to Objection 1. Sensible things are found in act outside the soul; and hence there is no need for an active sense. Wherefore it is clear that in the nutritive part all the powers are active, whereas in the sensitive part all are passive: but in the intellectual part, there is something active and something passive.

Reply to Objection 2. There are two opinions as to the effect of light. For some say that light is required for sight, in order to make colors actually visible. And according to this the active intellect is required for understanding, in like manner and for the same reason as light is required for seeing. But in the opinion of others, light is required for sight; not for the colors to become actually visible; but in order that the medium may become actually luminous, as the Commentator says on De Anima ii. And according to this, Aristotle's comparison of the active intellect to light is verified in this, that as it is required for understanding, so is light required for seeing; but not for the same reason.

Reply to Objection 3. If the agent pre-exist, it may well happen that its likeness is received variously into various things, on account of their dispositions. But if the agent does not pre-exist, the disposition of the recipient has nothing to do with the matter. Now the intelligible in act is not something existing in nature; if we consider the nature of things sensible, which do not subsist apart from matter. And therefore in order to understand them, the immaterial nature of the passive intellect would not suffice but for the presence of the active intellect which makes things actually intelligible by way of abstraction.


Whether the active intellect is something in the soul?

Objection 1. It would seem that the active intellect is not something in the soul. For the effect of the active intellect is to give light for the purpose of understanding. But this is done by something higher than the soul: according to John 1:9, "He was the true light that enlighteneth every man coming into this world." Therefore the active intellect is not something in the soul.

Objection 2. Further, the Philosopher (De Anima iii, 5) says of the active intellect, "that it does not sometimes understand and sometimes not understand." But our soul does not always understand: sometimes it understands, sometimes it does not understand. Therefore the active intellect is not something in our soul.

Objection 3. Further, agent and patient suffice for action. If, therefore, the passive intellect, which is a passive power, is something belonging to the soul; and also the active intellect, which is an active power: it follows that a man would always be able to understand when he wished, which is clearly false. Therefore the active intellect is not something in our soul.

Objection 4. Further, the Philosopher (De Anima iii, 5) says that the active intellect is a "substance in actual being." But nothing can be in potentiality and in act with regard to the same thing. If, therefore, the passive intellect, which is in potentiality to all things intelligible, is something in the soul, it seems impossible for the active intellect to be also something in our soul.

Objection 5. Further, if the active intellect is something in the soul, it must be a power. For it is neither a passion nor a habit; since habits and passions are not in the nature of agents in regard to the passivity of the soul; but rather passion is the very action of the passive power; while habit is something which results from acts. But every power flows from the essence of the soul. It would therefore follow that the active intellect flows from the essence of the soul. And thus it would not be in the soul by way of participation from some higher intellect: which is unfitting. Therefore the active intellect is not something in our soul.

On the contrary, The Philosopher says (De Anima iii, 5), that "it is necessary for these differences," namely, the passive and active intellect, "to be in the soul."

I answer that, The active intellect, of which the Philosopher speaks, is something in the soul. In order to make this evident, we must observe that above the intellectual soul of man we must needs suppose a superior intellect, from which the soul acquires the power of understanding. For what is such by participation, and what is mobile, and what is imperfect always requires the pre-existence of something essentially such, immovable and perfect. Now the human soul is called intellectual by reason of a participation in intellectual power; a sign of which is that it is not wholly intellectual but only in part. Moreover it reaches to the understanding of truth by arguing, with a certain amount of reasoning and movement. Again it has an imperfect understanding; both because it does not understand everything, and because, in those things which it does understand, it passes from potentiality to act. Therefore there must needs be some higher intellect, by which the soul is helped to understand.

Wherefore some held that this intellect, substantially separate, is the active intellect, which by lighting up the phantasms as it were, makes them to be actually intelligible. But, even supposing the existence of such a separate active intellect, it would still be necessary to assign to the human soul some power participating in that superior intellect, by which power the human soul makes things actually intelligible. Just as in other perfect natural things, besides the universal active causes, each one is endowed with its proper powers derived from those universal causes: for the sun alone does not generate man; but in man is the power of begetting man: and in like manner with other perfect animals. Now among these lower things nothing is more perfect than the human soul. Wherefore we must say that in the soul is some power derived from a higher intellect, whereby it is able to light up the phantasms. And we know this by experience, since we perceive that we abstract universal forms from their particular conditions, which is to make them actually intelligible. Now no action belongs to anything except through some principle formally inherent therein; as we have said above of the passive intellect (I:76:1. Therefore the power which is the principle of this action must be something in the soul. For this reason Aristotle (De Anima iii, 5) compared the active intellect to light, which is something received into the air: while Plato compared the separate intellect impressing the soul to the sun, as Themistius says in his commentary on De Anima iii. But the separate intellect, according to the teaching of our faith, is God Himself, Who is the soul's Creator, and only beatitude; as will be shown later on (I:90:3; I-II:3:7). Wherefore the human soul derives its intellectual light from Him, according to Psalm 4:7, "The light of Thy countenance, O Lord, is signed upon us."

Reply to Objection 1. That true light enlightens as a universal cause, from which the human soul derives a particular power, as we have explained.

Reply to Objection 2. The Philosopher says those words not of the active intellect, but of the intellect in act: of which he had already said: "Knowledge in act is the same as the thing." Or, if we refer those words to the active intellect, then they are said because it is not owing to the active intellect that sometimes we do, and sometimes we do not understand, but to the intellect which is in potentiality.

Reply to Objection 3. If the relation of the active intellect to the passive were that of the active object to a power, as, for instance, of the visible in act to the sight; it would follow that we could understand all things instantly, since the active intellect is that which makes all things (in act). But now the active intellect is not an object, rather is it that whereby the objects are made to be in act: for which, besides the presence of the active intellect, we require the presence of phantasms, the good disposition of the sensitive powers, and practice in this sort of operation; since through one thing understood, other things come to be understood, as from terms are made propositions, and from first principles, conclusions. From this point of view it matters not whether the active intellect is something belonging to the soul, or something separate from the soul.

Reply to Objection 4. The intellectual soul is indeed actually immaterial, but it is in potentiality to determinate species. On the contrary, phantasms are actual images of certain species, but are immaterial in potentiality. Wherefore nothing prevents one and the same soul, inasmuch as it is actually immaterial, having one power by which it makes things actually immaterial, by abstraction from the conditions of individual matter: which power is called the "active intellect"; and another power, receptive of such species, which is called the "passive intellect" by reason of its being in potentiality to such species.

Reply to Objection 5. Since the essence of the soul is immaterial, created by the supreme intellect, nothing prevents that power which it derives from the supreme intellect, and whereby it abstracts from matter, flowing from the essence of the soul, in the same way as its other powers.


Whether the active intellect is one in all?

Objection 1. It would seem that there is one active intellect in all. For what is separate from the body is not multiplied according to the number of bodies. But the active intellect is "separate," as the Philosopher says (De Anima iii, 5). Therefore it is not multiplied in the many human bodies, but is one for all men.

Objection 2. Further, the active intellect is the cause of the universal, which is one in many. But that which is the cause of unity is still more itself one. Therefore the active intellect is the same in all.

Objection 3. Further, all men agree in the first intellectual concepts. But to these they assent by the active intellect. Therefore all agree in one active intellect.

On the contrary, The Philosopher says (De Anima iii, 5) that the active intellect is as a light. But light is not the same in the various things enlightened. Therefore the same active intellect is not in various men.

I answer that, The truth about this question depends on what we have already said (Article 4). For if the active intellect were not something belonging to the soul, but were some separate substance, there would be one active intellect for all men. And this is what they mean who hold that there is one active intellect for all. But if the active intellect is something belonging to the soul, as one of its powers, we are bound to say that there are as many active intellects as there are souls, which are multiplied according to the number of men, as we have said above (I:76:2). For it is impossible that one same power belong to various substances.

Reply to Objection 1. The Philosopher proves that the active intellect is separate, by the fact that the passive intellect is separate: because, as he says (De Anima iii, 5), "the agent is more noble than the patient." Now the passive intellect is said to be separate, because it is not the act of any corporeal organ. And in the same sense the active intellect is also called "separate"; but not as a separate substance.

Reply to Objection 2. The active intellect is the cause of the universal, by abstracting it from matter. But for this purpose it need not be the same intellect in all intelligent beings; but it must be one in its relationship to all those things from which it abstracts the universal, with respect to which things the universal is one. And this befits the active intellect inasmuch as it is immaterial.

Reply to Objection 3. All things which are of one species enjoy in common the action which accompanies the nature of the species, and consequently the power which is the principle of such action; but not so as that power be identical in all. Now to know the first intelligible principles is the action belonging to the human species. Wherefore all men enjoy in common the power which is the principle of this action: and this power is the active intellect. But there is no need for it to be identical in all. Yet it must be derived by all from one principle. And thus the possession by all men in common of the first principles proves the unity of the separate intellect, which Plato compares to the sun; but not the unity of the active intellect, which Aristotle compares to light.


Whether memory is in the intellectual part of the soul?

Objection 1. It would seem that memory is not in the intellectual part of the soul. For Augustine says (De Trin. xii, 2,3,8) that to the higher part of the soul belongs those things which are not "common to man and beast." But memory is common to man and beast, for he says (De Trin. xii, 2,3,8) that "beasts can sense corporeal things through the senses of the body, and commit them to memory." Therefore memory does not belong to the intellectual part of the soul.

Objection 2. Further, memory is of the past. But the past is said of something with regard to a fixed time. Memory, therefore, knows a thing under a condition of a fixed time; which involves knowledge under the conditions of "here" and "now." But this is not the province of the intellect, but of the sense. Therefore memory is not in the intellectual part, but only in the sensitive.

Objection 3. Further, in the memory are preserved the species of those things of which we are not actually thinking. But this cannot happen in the intellect, because the intellect is reduced to act by the fact that the intelligible species are received into it. Now the intellect in act implies understanding in act; and therefore the intellect actually understands all things of which it has the species. Therefore the memory is not in the intellectual part.

On the contrary, Augustine says (De Trin. x, 11) that "memory, understanding, and will are one mind."

I answer that, Since it is of the nature of the memory to preserve the species of those things which are not actually apprehended, we must first of all consider whether the intelligible species can thus be preserved in the intellect: because Avicenna held that this was impossible. For he admitted that this could happen in the sensitive part, as to some powers, inasmuch as they are acts of corporeal organs, in which certain species may be preserved apart from actual apprehension. But in the intellect, which has no corporeal organ, nothing but what is intelligible exists. Wherefore every thing of which the likeness exists in the intellect must be actually understood. Thus, therefore, according to him, as soon as we cease to understand something actually, the species of that thing ceases to be in our intellect, and if we wish to understand that thing anew, we must turn to the active intellect, which he held to be a separate substance, in order that the intelligible species may thence flow again into our passive intellect. And from the practice and habit of turning to the active intellect there is formed, according to him, a certain aptitude in the passive intellect for turning to the active intellect; which aptitude he calls the habit of knowledge. According, therefore, to this supposition, nothing is preserved in the intellectual part that is not actually understood: wherefore it would not be possible to admit memory in the intellectual part.

But this opinion is clearly opposed to the teaching of Aristotle. For he says (De Anima iii, 4) that, when the passive intellect "is identified with each thing as knowing it, it is said to be in act," and that "this happens when it can operate of itself. And, even then, it is in potentiality, but not in the same way as before learning and discovering." Now, the passive intellect is said to be each thing, inasmuch as it receives the intelligible species of each thing. To the fact, therefore, that it receives the species of intelligible things it owes its being able to operate when it wills, but not so that it be always operating: for even then is it in potentiality in a certain sense, though otherwise than before the act of understanding—namely, in the sense that whoever has habitual knowledge is in potentiality to actual consideration.

The foregoing opinion is also opposed to reason. For what is received into something is received according to the conditions of the recipient. But the intellect is of a more stable nature, and is more immovable than corporeal nature. If, therefore, corporeal matter holds the forms which it receives, not only while it actually does something through them, but also after ceasing to act through them, much more cogent reason is there for the intellect to receive the species unchangeably and lastingly, whether it receive them from things sensible, or derive them from some superior intellect. Thus, therefore, if we take memory only for the power of retaining species, we must say that it is in the intellectual part. But if in the notion of memory we include its object as something past, then the memory is not in the intellectual, but only in the sensitive part, which apprehends individual things. For past, as past, since it signifies being under a condition of fixed time, is something individual.

Reply to Objection 1. Memory, if considered as retentive of species, is not common to us and other animals. For species are not retained in the sensitive part of the soul only, but rather in the body and soul united: since the memorative power is the act of some organ. But the intellect in itself is retentive of species, without the association of any corporeal organ. Wherefore the Philosopher says (De Anima iii, 4) that "the soul is the seat of the species, not the whole soul, but the intellect."

Reply to Objection 2. The condition of past may be referred to two things—namely, to the object which is known, and to the act of knowledge. These two are found together in the sensitive part, which apprehends something from the fact of its being immuted by a present sensible: wherefore at the same time an animal remembers to have sensed before in the past, and to have sensed some past sensible thing. But as concerns the intellectual part, the past is accidental, and is not in itself a part of the object of the intellect. For the intellect understands man, as man: and to man, as man, it is accidental that he exist in the present, past, or future. But on the part of the act, the condition of past, even as such, may be understood to be in the intellect, as well as in the senses. Because our soul's act of understanding is an individual act, existing in this or that time, inasmuch as a man is said to understand now, or yesterday, or tomorrow. And this is not incompatible with the intellectual nature: for such an act of understanding, though something individual, is yet an immaterial act, as we have said above of the intellect (I:76:1; and therefore, as the intellect understands itself, though it be itself an individual intellect, so also it understands its act of understanding, which is an individual act, in the past, present, or future. In this way, then, the notion of memory, in as far as it regards past events, is preserved in the intellect, forasmuch as it understands that it previously understood: but not in the sense that it understands the past as something "here" and "now."

Reply to Objection 3. The intelligible species is sometimes in the intellect only in potentiality, and then the intellect is said to be in potentiality. Sometimes the intelligible species is in the intellect as regards the ultimate completion of the act, and then it understands in act. And sometimes the intelligible species is in a middle state, between potentiality and act: and then we have habitual knowledge. In this way the intellect retains the species, even when it does not understand in act.


Whether the intellectual memory is a power distinct from the intellect?

Objection 1. It would seem that the intellectual memory is distinct from the intellect. For Augustine (De Trin. x, 11) assigns to the soul memory, understanding, and will. But it is clear that the memory is a distinct power from the will. Therefore it is also distinct from the intellect.

Objection 2. Further, the reason of distinction among the powers in the sensitive part is the same as in the intellectual part. But memory in the sensitive part is distinct from sense, as we have said (I:78:4. Therefore memory in the intellectual part is distinct from the intellect.

Objection 3. Further, according to Augustine (De Trin. x, 11; xi, 7), memory, understanding, and will are equal to one another, and one flows from the other. But this could not be if memory and intellect were the same power. Therefore they are not the same power.

On the contrary, From its nature the memory is the treasury or storehouse of species. But the Philosopher (De Anima iii) attributes this to the intellect, as we have said (Article 6, Reply to Objection 1). Therefore the memory is not another power from the intellect.

I answer that, As has been said above (I:77:3), the powers of the soul are distinguished by the different formal aspects of their objects: since each power is defined in reference to that thing to which it is directed and which is its object. It has also been said above (I:59:4) that if any power by its nature be directed to an object according to the common ratio of the object, that power will not be differentiated according to the individual differences of that object: just as the power of sight, which regards its object under the common ratio of color, is not differentiated by differences of black and white. Now, the intellect regards its object under the common ratio of being: since the passive intellect is that "in which all are in potentiality." Wherefore the passive intellect is not differentiated by any difference of being. Nevertheless there is a distinction between the power of the active intellect and of the passive intellect: because as regards the same object, the active power which makes the object to be in act must be distinct from the passive power, which is moved by the object existing in act. Thus the active power is compared to its object as a being in act is to a being in potentiality; whereas the passive power, on the contrary, is compared to its object as being in potentiality is to a being in act. Therefore there can be no other difference of powers in the intellect, but that of passive and active. Wherefore it is clear that memory is not a distinct power from the intellect: for it belongs to the nature of a passive power to retain as well as to receive.

Reply to Objection 1. Although it is said (3 Sent. D, 1) that memory, intellect, and will are three powers, this is not in accordance with the meaning of Augustine, who says expressly (De Trin. xiv) that "if we take memory, intelligence, and will as always present in the soul, whether we actually attend to them or not, they seem to pertain to the memory only. And by intelligence I mean that by which we understand when actually thinking; and by will I mean that love or affection which unites the child and its parent." Wherefore it is clear that Augustine does not take the above three for three powers; but by memory he understands the soul's habit of retention; by intelligence, the act of the intellect; and by will, the act of the will.

Reply to Objection 2. Past and present may differentiate the sensitive powers, but not the intellectual powers, for the reason give above.

Reply to Objection 3. Intelligence arises from memory, as act from habit; and in this way it is equal to it, but not as a power to a power.


Whether the reason is distinct from the intellect?

Objection 1. It would seem that the reason is a distinct power from the intellect. For it is stated in De Spiritu et Anima that "when we wish to rise from lower things to higher, first the sense comes to our aid, then imagination, then reason, then the intellect." Therefore the reason is distinct from the intellect, as imagination is from sense.

Objection 2. Further, Boethius says (De Consol. iv, 6), that intellect is compared to reason, as eternity to time. But it does not belong to the same power to be in eternity and to be in time. Therefore reason and intellect are not the same power.

Objection 3. Further, man has intellect in common with the angels, and sense in common with the brutes. But reason, which is proper to man, whence he is called a rational animal, is a power distinct from sense. Therefore is it equally true to say that it is distinct from the intellect, which properly belongs to the angel: whence they are called intellectual.

On the contrary, Augustine says (Gen. ad lit. iii, 20) that "that in which man excels irrational animals is reason, or mind, or intelligence or whatever appropriate name we like to give it." Therefore, reason, intellect and mind are one power.

I answer that, Reason and intellect in man cannot be distinct powers. We shall understand this clearly if we consider their respective actions. For to understand is simply to apprehend intelligible truth: and to reason is to advance from one thing understood to another, so as to know an intelligible truth. And therefore angels, who according to their nature, possess perfect knowledge of intelligible truth, have no need to advance from one thing to another; but apprehend the truth simply and without mental discussion, as Dionysius says (Div. Nom. vii). But man arrives at the knowledge of intelligible truth by advancing from one thing to another; and therefore he is called rational. Reasoning, therefore, is compared to understanding, as movement is to rest, or acquisition to possession; of which one belongs to the perfect, the other to the imperfect. And since movement always proceeds from something immovable, and ends in something at rest; hence it is that human reasoning, by way of inquiry and discovery, advances from certain things simply understood—namely, the first principles; and, again, by way of judgment returns by analysis to first principles, in the light of which it examines what it has found. Now it is clear that rest and movement are not to be referred to different powers, but to one and the same, even in natural things: since by the same nature a thing is moved towards a certain place. Much more, therefore, by the same power do we understand and reason: and so it is clear that in man reason and intellect are the same power.

Reply to Objection 1. That enumeration is made according to the order of actions, not according to the distinction of powers. Moreover, that book is not of great authority.

Reply to Objection 2. The answer is clear from what we have said. For eternity is compared to time as immovable to movable. And thus Boethius compared the intellect to eternity, and reason to time.

Reply to Objection 3. Other animals are so much lower than man that they cannot attain to the knowledge of truth, which reason seeks. But man attains, although imperfectly, to the knowledge of intelligible truth, which angels know. Therefore in the angels the power of knowledge is not of a different genus from that which is in the human reason, but is compared to it as the perfect to the imperfect.


Whether the higher and lower reason are distinct powers?

Objection 1. It would seem that the higher and lower reason are distinct powers. For Augustine says (De Trin. xii, 4,7), that the image of the Trinity is in the higher part of the reason, and not in the lower. But the parts of the soul are its powers. Therefore the higher and lower reason are two powers.

Objection 2. Further, nothing flows from itself. Now, the lower reason flows from the higher, and is ruled and directed by it. Therefore the higher reason is another power from the lower.

Objection 3. Further, the Philosopher says (Ethic. vi, 1) that "the scientific part" of the soul, by which the soul knows necessary things, is another principle, and another part from the "opinionative" and "reasoning" part by which it knows contingent things. And he proves this from the principle that for those things which are "generically different, generically different parts of the soul are ordained." Now contingent and necessary are generically different, as corruptible and incorruptible. Since, therefore, necessary is the same as eternal, and temporal the same as contingent, it seems that what the Philosopher calls the "scientific" part must be the same as the higher reason, which, according to Augustine (De Trin. xii, 7) "is intent on the consideration and consultation of things eternal"; and that what the Philosopher calls the "reasoning" or "opinionative" part is the same as the lower reason, which, according to Augustine, "is intent on the disposal of temporal things." Therefore the higher reason is another power than the lower.

Objection 4. Further, Damascene says (De Fide Orth. ii) that "opinion rises from the imagination: then the mind by judging of the truth or error of the opinion discovers the truth: whence" men's (mind) "is derived from" metiendo [measuring]. "And therefore the intellect regards those things which are already subject to judgment and true decision." Therefore the opinionative power, which is the lower reason, is distinct from the mind and the intellect, by which we may understand the higher reason.

On the contrary, Augustine says (De Trin. xii, 4) that "the higher and lower reason are only distinct by their functions." Therefore they are not two powers.

I answer that, The higher and lower reason, as they are understood by Augustine, can in no way be two powers of the soul. For he says that "the higher reason is that which is intent on the contemplation and consultation of things eternal": forasmuch as in contemplation it sees them in themselves, and in consultation it takes its rules of action from them. But he calls the lower reason that which "is intent on the disposal of temporal things." Now these two—namely, eternal and temporal —are related to our knowledge in this way, that one of them is the means of knowing the other. For by way of discovery, we come through knowledge of temporal things to that of things eternal, according to the words of the Apostle (Romans 1:20), "The invisible things of God are clearly seen, being understood by the things that are made": while by way of judgment, from eternal things already known, we judge of temporal things, and according to laws of things eternal we dispose of temporal things.

But it may happen that the medium and what is attained thereby belong to different habits: as the first indemonstrable principles belong to the habit of the intellect; whereas the conclusions which we draw from them belong to the habit of science. And so it happens that from the principles of geometry we draw a conclusion in another science—for example, perspective. But the power of the reason is such that both medium and term belong to it. For the act of the reason is, as it were, a movement from one thing to another. But the same movable thing passes through the medium and reaches the end. Wherefore the higher and lower reasons are one and the same power. But according to Augustine they are distinguished by the functions of their actions, and according to their various habits: for wisdom is attributed to the higher reason, science to the lower.

Reply to Objection 1. We speak of parts, in whatever way a thing is divided. And so far as reason is divided according to its various acts, the higher and lower reason are called parts; but not because they are different powers.

Reply to Objection 2. The lower reason is said to flow from the higher, or to be ruled by it, as far as the principles made use of by the lower reason are drawn from and directed by the principles of the higher reason.

Reply to Objection 3. The "scientific" part, of which the Philosopher speaks, is not the same as the higher reason: for necessary truths are found even among temporal things, of which natural science and mathematics treat. And the "opinionative" and "ratiocinative" part is more limited than the lower reason; for it regards only things contingent. Neither must we say, without any qualification, that a power, by which the intellect knows necessary things, is distinct from a power by which it knows contingent things: because it knows both under the same objective aspect—namely, under the aspect of being and truth. Wherefore it perfectly knows necessary things which have perfect being in truth; since it penetrates to their very essence, from which it demonstrates their proper accidents. On the other hand, it knows contingent things, but imperfectly; forasmuch as they have but imperfect being and truth. Now perfect and imperfect in the action do not vary the power, but they vary the actions as to the mode of acting, and consequently the principles of the actions and the habits themselves. And therefore the Philosopher postulates two lesser parts of the soul—namely, the "scientific" and the "ratiocinative," not because they are two powers, but because they are distinct according to a different aptitude for receiving various habits, concerning the variety of which he inquires. For contingent and necessary, though differing according to their proper genera, nevertheless agree in the common aspect of being, which the intellect considers, and to which they are variously compared as perfect and imperfect.

Reply to Objection 4. That distinction given by Damascene is according to the variety of acts, not according to the variety of powers. For "opinion" signifies an act of the intellect which leans to one side of a contradiction, whilst in fear of the other. While to "judge" or "measure" [mensurare] is an act of the intellect, applying certain principles to examine propositions. From this is taken the word "mens" [mind]. Lastly, to "understand" is to adhere to the formed judgment with approval.


Whether intelligence is a power distinct from intellect?

Objection 1. It would seem that the intelligence is another power than the intellect. For we read in De Spiritu et Anima that "when we wish to rise from lower to higher things, first the sense comes to our aid, then imagination, then reason, then intellect, and afterwards intelligence." But imagination and sense are distinct powers. Therefore also intellect and intelligence are distinct.

Objection 2. Further, Boethius says (De Consol. v, 4) that "sense considers man in one way, imagination in another, reason in another, intelligence in another." But intellect is the same power as reason. Therefore, seemingly, intelligence is a distinct power from intellect, as reason is a distinct power from imagination or sense.

Objection 3. Further, "actions came before powers," as the Philosopher says (De Anima ii, 4). But intelligence is an act separate from others attributed to the intellect. For Damascene says (De Fide Orth. ii) that "the first movement is called intelligence; but that intelligence which is about a certain thing is called intention; that which remains and conforms the soul to that which is understood is called invention, and invention when it remains in the same man, examining and judging of itself, is called phronesis [that is, wisdom], and phronesis if dilated makes thought, that is, orderly internal speech; from which, they say, comes speech expressed by the tongue." Therefore it seems that intelligence is some special power.

On the contrary, The Philosopher says (De Anima iii, 6) that "intelligence is of indivisible things in which there is nothing false." But the knowledge of these things belongs to the intellect. Therefore intelligence is not another power than the intellect.

I answer that, This word "intelligence" properly signifies the intellect's very act, which is to understand. However, in some works translated from the Arabic, the separate substances which we call angels are called "intelligences," and perhaps for this reason, that such substances are always actually understanding. But in works translated from the Greek, they are called "intellects" or "minds." Thus intelligence is not distinct from intellect, as power is from power; but as act is from power. And such a division is recognized even by the philosophers. For sometimes they assign four intellects—namely, the "active" and "passive" intellects, the intellect "in habit," and the "actual" intellect. Of which four the active and passive intellects are different powers; just as in all things the active power is distinct from the passive. But three of these are distinct, as three states of the passive intellect, which is sometimes in potentiality only, and thus it is called passive; sometimes it is in the first act, which is knowledge, and thus it is called intellect in habit; and sometimes it is in the second act, which is to consider, and thus it is called intellect in act, or actual intellect.

Reply to Objection 1. If this authority is accepted, intelligence there means the act of the intellect. And thus it is divided against intellect as act against power.

Reply to Objection 2. Boethius takes intelligence as meaning that act of the intellect which transcends the act of the reason. Wherefore he also says that reason alone belongs to the human race, as intelligence alone belongs to God, for it belongs to God to understand all things without any investigation.

Reply to Objection 3. All those acts which Damascene enumerates belong to one power—namely, the intellectual power. For this power first of all only apprehends something; and this act is called "intelligence."

Secondly, it directs what it apprehends to the knowledge of something else, or to some operation; and this is called "intention." And when it goes on in search of what it "intends," it is called "invention." When, by reference to something known for certain, it examines what it has found, it is said to know or to be wise, which belongs to "phronesis" or "wisdom"; for "it belongs to the wise man to judge," as the Philosopher says (Metaph. i, 2). And when once it has obtained something for certain, as being fully examined, it thinks about the means of making it known to others; and this is the ordering of "interior speech," from which proceeds "external speech." For every difference of acts does not make the powers vary, but only what cannot be reduced to the one same principle, as we have said above (I:78:4).