QUAESTIONES DISPUTATAE DE ANIMA

ARTICLE 2

WHETHER THE HUMAN SOUL, SO FAR AS ITS ACT OF EXISTING IS CONCERNED, IS SEPARATED FROM THE BODY

[Summa theol., la, q-75, a-4; Contra Gentiles, 11 1 57; Sent., Bk. III, dist., 5, q. 3, a. 2; dist., 22, q. i, a. i; De ente et essentia, chap. 2; De unit. intell.; Comm. in Metaph., VII, lect. 9]

In the second article we examine this question: Whether the human soul, so far as its act of existing is concerned, is separated from the body.

Objections.

1. It seems that it is. For the Philosopher says in the De anima [III, 4, 429b 4] that no sentient power exists without a body. But the intellect is separate and the intellect is the human soul. Therefore the human soul, so far as its act of existing is concerned, is separated from the body.

2. Further, the soul is the act of a physical organic body inasmuch as the body is its organ. Hence, if the intellect, with respect to its very act of existing, is united as a form to the body, the body must be its organ. This is impossible, as the Philosopher proves in the De anima [ibid.].

3. Further, a form is united to matter more intimately than a power is to an organ. But the intellect cannot be united to the body as a power is to an organ, because the intellect is simple.

4. But it might be said that the intellect, that is, the intellective power, does not have an organ, but that the essence itself of the intellective soul is united as a form to the body. On the other hand, no effect is simpler than its cause. Now a power of the soul is an effect of its essence, because all powers of the soul flow from its essence (esse). Consequently no power of the soul is simpler than its essence. If, then, the intellect cannot be the act of the body, as is proved in the De anima [III. 4, 420a 24; 420b 4] neither can the intellective soul be united as a form to the body.

5. Further, every form united to matter is individuated by matter. Therefore, if the intellective soul is united to the body as the form of the latter, the soul must be an individuated [form]. Then the forms received in the soul are individuated forms. Consequently the intellective soul will be incapable of knowing universals; which is clearly false.

6. Further, a universal form does not acquire its universality from the thing existing outside the soul, because all forms existing in such things are individuated. Thus, if the forms in the intellect are universal, they must acquire this universality from the intellective soul. Consequently the intellective soul is not an individuated form, and therefore is not united to the body so far as its act of existing is concerned.

7. However, it might be said that inasmuch as intelligible forms inhere in the soul they are individuated; but as the likenesses of things they are universals representing things according to their common nature and not according to their individuating principles. On the contrary, since a form is a principle of operation, an operation proceeds from a form in accordance with the manner in which that form inheres in a subject. For instance, the hotter something is, the more it is capable of heating. Therefore, if the species of things in the intellective soul are individuated because they inhere in the soul, then the knowledge which results will be knowledge only of the individual [as such] and will not be universal.

8. Further, the Philosopher says in the De anima [II, 3, 414b 27], that just as the triangle is contained in the quadrilateral and the quadrilateral in the pentagon, so also is the nutritive part of the soul contained in the sentient part and the sentient in turn contained in the intellective. However, the triangle is not contained actually in the quadrilateral, but only potentially; nor is the quadrilateral contained actually in the pentagon. Therefore, neither is the nutritive nor sentient part of the soul contained, actually in the intellective. Consequently, since the intellective part of the soul is united to the body only through the intermediary of the nutritive and sentient parts, because the sentient and nutritive parts of the soul are not actually contained in the intellective part, the intellective part of the soul will not be united to the body.

9. Further, the Philosopher says in the De generatione animalium [II, 3, 736b 2] that a man is not at once both an animal and a man, but first is an animal and then a man. Consequently the principle whereby he is an animal and that whereby he is a man are not one and the same. But he is an animal because of his sentient part and a man because of his intellective part. Therefore the sentient and intellective parts are not united in one and the same substance of the soul. Hence the conclusion is the same as the foregoing.

10. Further, a form belongs to the same genus as the matter to which it is united. But the intellect does not belong to the genus of corporeal things. Therefore the intellect is not a form united to the body as to matter.

11. Further, one being does not result from the union of two actually existing substances. But both the body and the intellect [i.e., the intellective soul] are two actually existing substances. Hence the intellect cannot be united to the body so that one being results from their union.

12. Further, every form united to matter is given actual existence by moving and changing matter. But the intellective soul is not given actual existence [by being educed] from the potentiality of matter, but receives its act of existing from an extrinsic agent, as the Philosopher says in the De generatione animalium [ibid., 736b 27]. Therefore the soul is not a form united to matter.

13. Further, a thing operates in accordance with its nature. But the intellective soul has an operation of its own without the body, namely, the act of intellection. Therefore, so far as its act of existing is concerned, the intellective soul is not united to the body.

14. Further, even the slightest impropriety is impossible for God.” But it is improper for an innocent soul to be united to a body which is like a prison. Therefore it is impossible for God to unite an intellective soul to a body.

15. Further, a wise artifex does not place an obstacle in the way of his work. But the body is the greatest obstacle to the intellective soul in acquiring knowledge of truth, in which its perfection consists, according to that text in the Book of Wisdom: “The body which is corrupted, weighs down upon the soul” (Wis. 9:15). Therefore God did not unite the intellective soul to the body.

16. Further, things which are united one to another have an affinity for each other. But the intellective soul and the body are opposed to each other, because “The flesh desires the opposite of the spirit, and the spirit, the opposite of the flesh” (Gal. 5:17). Consequently the intellective soul is not united to the body.

17. Further, the intellect is in potency to all intelligible forms having none actually, just as prime matter is in potency to all sensible forms having none actually. But it is for this reason that there is one prime matter for all things. Therefore there is also one intellect for all men. Hence it is not united to a body which would individuate it.

18. Further, the Philosopher proves in the De anima [III, 4, 429a 18] that, if the possible intellect had a bodily organ, it would have a certain determinate sensible nature, and thus could not receive and know all sensible forms. But a form is united to matter more intimately than a power is to an organ. Therefore, if the intellect is united as a form to the body, it will have a certain determinate sensible nature, and thus will be incapable of perceiving and knowing all sensible forms. This is impossible.

19. Further, every form united to matter is received in matter. But whatever is received in a thing exists therein in accordance with the mode of the recipient. Therefore every form united to matter exists in matter according to the mode of matter. But the mode of sensible and corporeal matter is not the one that a thing receives through an intelligible mode. Consequently, since the intellect has an intelligible mode of existing, it is not a form united to corporeal matter.

20. Further, if the soul is united to corporeal matter, it must be received in it. But whatever is received in a thing that has received its act of existing from matter, is received in matter. Therefore, if the soul is united to matter, then whatever is received in the soul is received in matter. But the forms of the intellect cannot be received in prime matter. On the contrary, they are made intelligible by abstraction from matter. Consequently, a soul which is united to corporeal matter is not capable of receiving intelligible forms, and thus the intellect, which is capable of receiving intelligible forms, will not be united to corporeal matter.

On the contrary, the Philosopher says in the De anima [II, 1, 412b 6], that it is unnecessary to ask whether the soul and the body are one, just as it is unnecessary to ask whether the wax and its impression are one. But with respect to its act of existing, the impression cannot be separated in any way from the wax. Consequently, with respect to its act of existing, the soul is not separated from the body. But the intellect is a part of the soul, as the Philosopher says in the De anima [III, 4, 429a 15]. Therefore the intellect, so far as its act of existing is concerned, is not separated from the body.

Further, so far as its act of existing is concerned, no form is separated from matter. But the intellective soul is the form of the body. Therefore, with respect to its act of existing, the soul is not separated from matter.

I answer: In order to settle this issue we must take into consideration that, whenever a thing is found to be sometimes in potency and sometimes in act, there must be some principle by which it is in potency; just as a man is sometimes actually sensing and sometimes only potentially. Now on account of this it is necessary to maintain that in man there exists a sentient principle which is in potency to sensible things; for if he were always actually sensing, the forms of sensible things would always actually exist in his sentient principle. Similarly, since a man is found sometimes to be actually understanding and sometimes only potentially, it is necessary to maintain that in man there exists an intellective power which is in potency to intelligibles; and the Philosopher, in the De anima [III, 5, 430a 15], calls this principle the possible intellect. Consequently this possible intellect must be in potency to all things intelligible to man; it must be capable of receiving them and therefore must be devoid of them, because anything capable of receiving other things is in potency to them inasmuch as it lacks them; just as the pupil of the eye, which is capable of receiving all colors, lacks every color. Now man is determined by nature to understand the forms of all sensible things. Therefore, by its very nature the possible intellect must be devoid of all sensible forms and natures, and so also must have no bodily organ. For if it had a bodily organ, it would be limited to some sensible nature, just as the power of vision is limited to the nature of the eye. By means of this proof we exclude the position of the ancient philosophers, who held that the intellect did not differ from the sentient powers, as well as the position of those who maintained that the principle by which a man understands is a certain form or power which is united to the body as other material forms or powers are.

But certain other men avoiding this position, fall into the opposite error. For they think that the possible intellect is devoid of every sensible nature and that it is not present in the body, because it is a certain substance which exists in separation from the body and is in potency to all intelligible forms. But this position cannot be maintained, because we acquire our knowledge of the possible intellect only so far as a man understands by it. Indeed, this is the way Aristotle obtains his knowledge of it, as is evident from what he says in the De anima [III, 4, 429a 10] when he begins to discuss the possible intellect: “Concerning that part of the soul by which the soul knows and perceives... it must be considered...”; and in another place he says: “I speak of the possible intellect by which the soul understands.” But if the possible intellect were a separate substance, it would be impossible for a man to understand by means of it; because, if a substance performs an operation, that operation cannot belong to any other substance than the one performing it. For although one of two substances can be the cause of the other’s operation, as the principal agent is the cause of the activity of the instrument, nevertheless the action of the principal agent is not numerically the same as that of the instrument. For the action of the principal agent consists in moving the instrument, whereas that of the instrument consists in being moved by the principal agent and in moving something else. Consequently, if the possible intellect is a substance existing apart from this or that particular man, it is impossible for the possible intellect’s act of intellection to be the act of any particular man. From this it follows that no man understands anything, because the act of intellection is not attributed to any principle in man except the possible intellect. Hence the same manner of arguing is opposed to this position and to those who deny its principles, as is evident from Aristotle’s arguments against them in the Metaphysics [IV, 3, 1005b 25].

Now Averroes who is a follower of this position, intending to avoid its incongruity maintained that, although the possible intellect existed apart from the body, it must be united to man through the intermediary of phantasms. For phantasms, as the Philosopher says in the De anima [III, 5, 430a 14], are related to the possible intellect as sensible things are to sense, and colors to sight. Thus an intelligible species has two subjects: one in which it exists with an intelligible mode of existing, and this is the possible intellect: another in which it exists with a real mode of existing, and this subject is the phantasms. Therefore [according to Averroes] there is a certain union of the possible intellect with the phantasms inasmuch as an intelligible species exists in a certain manner in each of these subjects; and a man understands through the [supposedly separate] possible intellect as a result of this union with the phantasms.

However, this union is still not sufficient [to account for man’s knowledge], for a thing is capable of knowing, not because intelligible species are present to it, but because it possesses a cognitive power. Now evidently, from what has been said, intelligible species alone will be present to man, whereas the power of understanding, that is, the possible intellect,. exists in complete separation from him. Therefore it does not follow from the aforesaid union that a man will have what is necessary for understanding, but only that a species or something in that intellect will be understood. This clearly appears to be the case from the simile introduced above. For if phantasms are related to the intellect as colors are to sight, the union of the [supposedly separate] possible intellect with us through our phantasms, will be the same as that of sight with a wall through its colors. Now it does not follow that a wall sees because it has colors, but only that it is seen. Nor, similarly, does it follow that a man will understand because phantasms are present within him, but only that he will be understood.

Furthermore, a phantasm is not the subject of an intelligible species inasmuch as the latter is actually understood. On the contrary, an intelligible species is made to be actually understood by abstraction from phantasms. Moreover, the possible intellect is the subject of an intelligible species only inasmuch as an intelligible species is now actually understood and abstracted from phantasms. Therefore the species existing in the possible intellect, and that existing in the phantasms. through which the [supposedly separate] possible intellect is united to us, are not one and the same.

Furthermore, if anyone understands through intelligible species only when they are actually understood, it follows, according to the aforesaid position, that we are incapable of understanding anything in any way, for then intelligible species would be present to us only inasmuch as they exist in phantasms, and here they are only potentially understood. Consequently it is evident on the side of our human nature that the above-mentioned position is impossible. This is also apparent from the nature of separate substances. Since these are most perfect, it is impossible for them in their own operations to stand in need of the operations of material things; nor need they be in potency to any things of this kind, for not even the celestial bodies, which are below the separate substances, require things of this sort. Hence, since the possible intellect is in potency to the species of sensible things, and since its operation may not be completed without phantasms, which depend on our operations, it is impossible and inconceivable for the possible intellect to be one of the separate substances.

Consequently, we must say that the possible intellect is a certain faculty or power of the human soul. For although the human soul is a form united to the body, it is not embraced completely by the body as though immersed in it as other material forms are, but transcends the capacity of the whole of corporeal matter. And so far as the soul transcends corporeal matter, the potentiality for intelligibles exists in the soul and this [potentiality] belongs to the possible intellect. Certainly the soul, so far as it is united to the body, has operations and powers in common with the body; such, for example, are the powers of the nutritive and sentient part. Thus the nature of the possible intellect is as Aristotle proves it to be,110 for the possible intellect is not a power rooted in any bodily organ. However, a man understands formally by means of it inasmuch as it is rooted in the essence of the human soul, which is the form of man.

Answers to objections.

1. The intellect is said to be separate but not the senses; because the intellect remains in the separated soul when the body has corrupted, whereas the senses do not. Or a better way of stating it is to say that the intellect is said to be separate because it does not employ a bodily organ in its operation as the senses do.

2. The human soul is the act of an organic body because the body is its organ. However, the body need not be the organ of all the soul’s active and passive powers, since the human soul exceeds the capacity of the body, as we have explained.

3. The organ of a power is the principle of that power’s operation. Hence, if the possible intellect were united to an organ, its operation would also be the operation of that organ, and thus it would be impossible for the principle by which we understand, to lack every sensible nature. For this principle by which we understand would then be the possible intellect together with its organ, just as the principle whereby we see, namely, the power of vision, exists concurrently with the pupil of the eye. However, even though the human soul is the form of the body and the possible intellect is one of the soul’s powers, it. does not follow that the possible intellect is limited to some sensible nature; because the human soul transcends the capacity (proportionem) of the body, as we have explained.

4. The possible intellect belongs to the human soul inasmuch as the soul is elevated above corporeal matter. Consequently, because the intellect is not the act of an organ, it does so Aristotle proved that the intellect is “separate,” not in the sense of existing apart from man, but as being free from matter in its operation.

5. The human soul is an individuated form and so also is its power which is called the possible intellect, as well as the intelligible forms which are received in the possible intellect. But this does not prevent these forms from being actually known, for a thing is actually known because it is immaterial, not because it is universal. Indeed, the universal is intelligible because it is abstracted from material individuating conditions. Moreover, it is evident that separate substances are actual intelligibles and yet are certain individual entities; just as Aristotle says in the Metaphysics [VII, 14, 1039a 23], that the separated forms which Plato claimed to exist, were individual things. Therefore if individuation is incompatible with intelligibility it is evident that the same difficulty remains when the intellect is considered to be a separate substance; for then the possible intellect would be individuated as well as the species which are receivcd in it. Consequently we must understand that, although the intelligible species received in the possible intellect are individuated inasmuch as they exist in the possible intellect, still the universal, which is conceived by abstraction from individuating principles, is known in these species inasmuch as they are immaterial. For universals with which the sciences are concerned, are what are known (through intelligible species) and not the intelligible species themselves. Moreover, concerning these intelligible species, not all sciences study them, but only physics and metaphysics. For an intelligible species is that by which the intellect knows, but not that which it knows—except by reflection inasmuch as it knows that by which it knows in order to know itself.

6. The intellect gives universality to the forms known inasmuch as it abstracts them from material individuating conditions. Consequently it is not necessary that the intellect be universal, but that it be immaterial.

7. The species of an operation is a natural effect of the species of the form which is the principle of that operation, whereas the ineffectiveness of an operation is a natural effect of the form inasmuch as it inheres in a subject. For a thing heats because it is hot, but it heats more or less effectively according as heat perfects it to a greater or lesser degree. Now to understand universals pertains to the species of intellectual operation. Hence this activity is the natural effect of an intellectual species as its proper operation; but so far as this activity is exercised more or less perfectly by the one understanding, it follows that the one understanding does so in a more or less perfect way.

8. The resemblance which the Philosopher observes between geometrical figures and the parts of the soul is to be regarded in this way: that just as a quadrilateral contains the elements of a triangle and additional characteristics; and a pentagon, the elements of a quadrilateral; so also does the sentient soul possess the characteristics of the nutritive, and the intellective possesses the characteristics of the sentient and others as well. Therefore it is not shown in this way that the nutritive and sentient parts of the soul differ essentially from the intellective, but rather that one of these [parts] contains another.

9. just as animal and man are not conceived simultaneously, so neither are animal and horse, as the Philosopher points out in the same place. Therefore this statement [of the Philosopher] is not based on the argument that the sentient soul, existing substantially in man, is a principle by which he is an animal, and the intellective soul another principle by which he is a man. For it cannot be said that there are many different principles in a horse, one making it an animal, another, a horse. But this statement [of the Philosopher] is made for this reason, that in the concept of animal the imperfect operations appear first, and then the more perfect; just as every generation is a transition from the imperfect to the perfect.

10. A form does not belong to a genus, as has been shown (Art. 1). Consequently, since the intellective soul is the form of man, it does not belong to a different genus from that of the body. But each belongs to the genus animal and the species man, by reduction.

11. One being does not result from the union of two actually existing substances complete in their species and nature. Now the soul and the body are not substances of this sort, because they are parts of human nature. Therefore nothing prevents them from being united to form one being [substantially].

12. Although the human soul is a form united to a body, it totally transcends the capacity of the whole of corporeal matter, and therefore cannot derive actual existence from the potentiality of matter as a result of any motion or change, as do other forms which are immersed in matter.

13. The soul, through that part of it whereby it exceeds every capacity of the body, has an operation in which the body does not share. However this does not prevent the soul from being united to the body in some way.

14. This objection agrees with the position of Origen, who maintained that in the beginning souls were created without bodies together with the spiritual substances [i.e., the angels] and afterwards were united to bodies as though shut up in prisons. However, he did not say souls suffered that innocently, but because of a preceding sin. Hence Origen, in accordance with the position of Plato, held that the human soul was a complete species in itself, and that the body was joined to it accidentally. But since this is false, as we have shown above (Art. 1), it is not detrimental to the soul to be united to a body; on the contrary this union makes for the perfection of its nature. However, that the body is the prison of the soul and taints the soul, is merited by the first sin.

15. It is natural to the human soul to apprehend intelligible truth in a manner inferior to that proper to superior spiritual substances, namely, by abstraction from sensible things. But in this also the soul suffers an impediment through the corruption of the body which results from the sin of the first parent.

16. The fact that the flesh desires things that are opposed to the spirit, shows the affinity of the soul for the body. For “spirit” signifies the superior part of the soul whereby man surpasses other animals, as Augustine says in the Super Genesi contra Manichaeos [II, 8]. But the flesh is said to desire because the parts of the soul joined to the flesh desire those things, which delight the flesh, and now and again these concupiscences fight against the spirit.

17. The possible intellect does not possess any intelligible form actually, but only potentially, just as prime matter does not have any sensible form actually. Therefore it is not necessary, nor does the argument prove, that the possible intellect is one and the same for all men. It only shows that their intellect is ope with respect to all intelligible forms, just as prime matter is one with respect to all sensible forms.

18. If the possible intellect had a bodily organ, that organ would have to be a principle [of understanding] together with the possible intellect which is the cause of intellection; just as the pupil of the eye together with the power of vision is the principle of vision; and thus the principle by which we understand would have a determinate sensible nature. This is evidently false in view of Aristotle’s demonstration which was given above. However, this does not follow from the fact that the soul is the form of the body, because the possible intellect is a power of the soul so far as it transcends the capacity of the body.

19. Although the soul is united to the body in accordance with the body’s mode of existing, still the soul has an intellectual nature in virtue of that part whereby it transcends the capacity of the body; and thus the forms received in the soul are intelligible and not material.

Whence the solution to the twentieth objection is evident.

ARTICLE III

WHETHER THERE IS ONE POSSIBLE INTELLECT, OR INTELLECTIVE SOUL, FOR ALL MEN

[Summa theol., la, q.76, a.2; Contra Gentiles, II, 59, 73, 75; Sent., I, dist., 8, q.5, a.2, ad 6; II, dist., 17, q.2, a.1; De spir. creat., a.9; De unit. intell.; Compend. theol., 58.]

In the third article we examine this question: Whether there is one possible intellect, or intellective soul, for all men.

Objections.

1. It seems that there is. For a perfection is proportioned to what is perfectible. But truth is the perfection of the intellect, for truth is the good of the intellect, as the Philosopher says in the Ethics [VI, 2, 1139b 11]. Therefore, since truth, which. all men understand, is one, it seems that there is one possible intellect for all men.

2. Further, Augustine says, in the book De quantitate animae [32] “I know what I will say to you about the number of souls.... For if I say there is one soul, you will be disturbed, because it is happy in one and sad in another, and one and the same thing cannot be happy and sad. If I say one and many at the same time, you will laugh; nor is it easy for me to know how to suppress your laughter. For if I say there are many only, I will laugh at myself, and I will maintain that I am less displeasing to myself than to you.” Therefore the existence of many souls, one for each man, seems to be ridiculous.

3. Further, things that differ from each other, differ because of the determinate nature which each possesses. But the possible intellect is in potency to all forms, having none actually. Consequently the possible intellect [in one man] cannot differ [from that in another], and thus there cannot be many possible intellects, one for each man.

4. Further, the possible intellect totally lacks everything that it knows, because, prior to actual intellection, it possesses none of the things that it is cognizant of, as is said in the De anima [III, 4, 429a 18]. But, as is said in the same book, it completely lacks any nature of its own; and thus it cannot have a multiple existence among different individuals.

5. Further, there must be something in common in all things that are distinct and multiple, for man is common to many men, and animal to many animals. But the possible intellect does not have anything in common with other things, as is said in the De anima [III, 4, 429a 23]. Therefore the possible intellect in one man cannot differ from that in another, and thus there cannot be many possible intellects, one for each man.

6. Further, as Rabbi Moses points out, there is multiplicity with respect to cause and thing caused only in things existing in separation from matter. But the intellect or soul of one man is not the cause of the intellect or soul of another. Therefore, since the possible intellect is separate, as is said in the De anima [III, 5, 429a 24], there will not be many possible intellects, one for each man.

7. Further, the Philosopher says, in the De anima [III, 7&8, 431a 1; 431b 21], that the intellect and what is understood are one and the same. But what is understood is one and the same for all men. Therefore there is one possible intellect for all men.

8. Further, that which is understood is a universal, which is a one-in-many (unum in multis). But the form understood does not derive this unity from the thing [of which it is the form], for the form man is present in men themselves only as individuated and multiplied among diverse men. Therefore the form derives this unity from the intellect. Consequently there is one [possible] intellect for all men.

9. Further, the Philosopher says in the De anima [III, 4, 429a 26] that the soul is the place (locus) of species. But place is common to different things in place. Therefore there are not many souls, one for each man.

10. But it must be said that the soul is the place of species because if contains species. On the other hand, just as the intellect contains intelligible species, so does sense contain sensible species. Therefore, if the intellect is the place of species because it contains them, sense, for a similar reason, will also be the place of species. This is contrary to what the Philosopher says, in the De anima [ibid.] that not every soul is the place of species, but only the intellective soul.

11. Further, a thing operates only in the place in which it is located. But the possible intellect operates everywhere, for it understands things existing in heaven, those existing on earth, and everywhere. Therefore the possible intellect is everywhere, and thus is one for all men.

12. Further, whatever is limited (definitum) to some one particular thing, has a determinate matter, because the principle of individuation is matter. But the possible intellect does .not have a determinate matter, as is proved in the De anima [III, 8, 431b 30]. Therefore it is not found to exist in each particular man, and thus is one for all men.

13. But it must be said that the possible intellect has matter in the thing in which it exists, namely, in the human body in which it is confined. On the other hand, the principle of individuation should belong to the individuated essence. But the body is not an essential part of the possible intellect. Therefore the possible intellect cannot be individuated by the body, and consequently cannot have a multiple existence.

14. Further, the Philosopher says in the De caelo [I, 9, 279a 8] that if there were many worlds, there would be many first heavens. But if there were many first heavens, there would be many first movers; and thus these first movers would be material. Therefore, for a similar reason, if there were many possible intellects, one for each man, the possible intellect would be material; which is impossible.

15. Further, if there are many possible intellects, one for each man, they must remain many when their bodies have corrupted. But then, since they can differ only as regards form, they will have to differ specifically. Therefore, since possible intellects do not become specifically different when their bodies have corrupted (because nothing is changed from one species into another unless it is corrupted), possible intellects were specifically different before their bodies corrupted. But man acquires his species from the intellective soul. Therefore diverse men do not possess the same species; which is clearly false.

16. Further, whatever exists in separation from a body cannot be given a multiple existence by bodies. But the possible intellect is separate from the body, as the Philosopher proves in the De anima [III, 5, 430a 79]. Therefore the possible intellect cannot be multiplied nor be individuated by bodies. Consequently there are not many possible intellects, one for each man.

17. Further, if a possible intellect exists in each man, intelligible species must exist in each man; and thus it follows that intelligible species are individuated forms. But individuated forms are only potentially intellected, for the universal, which is the proper object of intellection, must be abstracted from such forms. Therefore the forms which are in the possible intellect will only be potentially intelligible, and thus the possible intellect will be unable to be actually understood; which is incongruous.

18. Further, an agent and patient, mover and thing moved, have something in common. Now a phantasm is related to the possible intellect, existing in us, as an agent to a patient, and as a mover to something moved. Therefore the intellect existing in us has something in common with phantasms. But the possible intellect has nothing in common with the latter, as is pointed out in the De anima [III, 4, 429b 22]. Therefore the [supposedly separate] ‘possible intellect differs from the intellect which is present in us, and so is not multiplied among diverse men.

19. Further, a thing, inasmuch as it exists, is one. Therefore neither its act of existing nor its unity depends on another. But the possible intellect’s act of existing does not depend on the body, otherwise it would be corrupted when the body corrupts. Consequently the unity of the possible intellect does not depend on the body; and so neither does its multiplicity. Therefore the possible intellect is not multiplied among different bodies [in such a way that each man possesses his own].

20. Further, the Philosopher says, in the Metaphysics [VII, 2, 1043b 1] that in those things which are forms alone [i.e., not composed of matter and form], the thing and its quiddity (quod quid erat esse), that is, the nature of its species, are one and the same. But the possible intellect, or intellective soul, is a form alone, for, ‘if it were composed of matter and form, it would not be the form of anything else. Hence the intellective soul is the nature itself of its species. So, if the nature of the species is one and the same in every intellective soul, the intellective soul is incapable of having a multiple existence among diverse individuals [in such a way that each possesses his own].

21. Further, the soul has a multiple existence among different bodies only by being united thereto. But the possible intellect belongs to that part of the soul which transcends bodily union. Hence the possible intellect does not have a multiple existence among diverse men [in such a way that each possesses his own intellect].

22. Further, if many human souls exist because of the multiplicity of bodies, and many possible intellects because of the multiplicity of souls, and since it is certain that there must be many intelligible species if there are many possible intellects, it follows that the first principle of multiplicity must be corporeal matter. But whatever is made multiple by matter is individual, and is not actually intelligible. Therefore the species which are in the possible intellect will not be actually intelligible objects; which is incongruous. Hence there will not be many human souls and possible intellects, one in each man.

On the contrary, man understands by the possible intellect. For it is said in the De anima [III, 5, 430a 15] that the possible intellect is that by which the soul understands. Consequently, if there is one possible intellect for all men, it follows that one man understands what another does; which is clearly false.

Further, the intellective soul is related to the body as a form to matter, and as a mover to an instrument. But every form requires a determinate matter, and every mover a determinate instrument. It is impossible, therefore, that there be one intellective soul for all men.

I answer: This question depends in a certain way on the preceding one. For if the possible intellect is a substance having existence separate from the body, it must be unique; because those things which have existence apart from a body can in no way have a multiple existence as a result of a multiplicity of bodies. However, the unicity of the intellect must be given special consideration because it involves a peculiar difficulty. For it is at once apparent that there cannot be one [possible] intellect for all men. It is, indeed, clear that the possible intellect is related to the perfections, which sciences are, as a primary perfection to a secondary one, and that we have scientific knowledge potentially because of a possible intellect. This fact compels us to maintain that a possible intellect exists. Moreover, it is obvious that not all men possess the same scientific knowledge, because some know sciences which others do not. Now it is evidently incongruous and impossible for one and the same primary subject to be in act and in potency with regard to the same form. For example, [it is impossible that] a surface be at,the same time potentially and actually white.

Now those maintaining that there is one possible intellect for all men try to avoid the absurdity of this position by pointing to the fact that the intelligible species, on which the perfection of science is based, have a twofold subject, as was shown above (Art. 2), namely, the phantasms, themselves, and the possible intellect. And they argue that intelligible species are not the same in all men, because phantasms are not the same in all. In fact, as existing in the possible intellect, intelligible species are not multiple. So it is that one man possesses a science which another lacks, because he has different phantasms. But this is evidently foolish in view of what has previously been said. For species are actually intelligible only by being abstracted from phantasms and by existing in the possible intellect. Therefore diversity of phantasms cannot be the cause of the unity or multiplicity of a perfection having the character of scientific knowledge. Nor do scientific habits exist in some part of the sentient soul as their subject, as these men claim.

But an even greater difficulty faces those who maintain that there is one possible intellect for all men. For it is evident that the act of intellection has its origin in the possible intellect as the first principle whereby we understand, just as the operation of sensing has its origin in a sentient power. Also, while it was shown above (Art. 2) that if the possible intellect exists apart from man, the act of understanding, which belongs to the possible intellect, cannot be the operation of this or that man; nevertheless, from the hypothesis of one possible intellect for all men, it follows that this or that man understands by the possible intellect’s own act of understanding. Yet an operation can be multiplied in only two ways: either on the side of the objects [known], or on that of the principle operating. A third way [of multiplying operation] can also be envisaged from the point of view of time, as, for instance, when an operation involves temporal changes. Hence the act of understanding, which is the operation of the intellect, can be multiplied with respect to objects known, so that it is one thing to know a man, another thing to know a horse. The act of understanding can also be multiplied with respect to time, so that to understand what happened yesterday is one act, and to understand what happens today, another, if, of course, the operation is not continuous. However, the act of understanding cannot be multiplied respecting the principle operating, if there is only one possible intellect. Therefore, if the possible intellect’s own act of understanding is this or that man’s act of understanding, this man’s act of understanding, and that man’s, could be different if they were understanding different things. A reason for this can be found in the diversity of phantasms. The act of understanding by different men understanding the same thing, according to the one possible intellect theory, could be multiplied similarly, so that one understands today and another tomorrow. This can also be attributed to the different use of phantasms. But in the case of two men who understand the same thing at the same time, their act of understanding would have to be numerically one and the same; which is clearly impossible. Therefore it is impossible for the possible intellect, by which we understand formally, to be one and the same for all men.

However, it would be more reasonable to hold that we understand by the possible intellect as an active principle existing in us, and causing in us actual understanding. For one mover puts different things into operation; but that different things should act through some one thing formally, is absolutely impossible.

Moreover, the forms and species of natural things are known through their proper operations; but the proper operation of man, as man, is understanding and reasoning. Hence the principle of this operation, whereby man is made to be specifically what he is, must be the intellect. It cannot be the sensory soul, nor any other power of man. Therefore, if the possible intellect, existing as a separate substance, is one for all men, then all men are made to be specifically what they are by one substance existing apart from them. This position is reminiscent of the doctrine of Ideas, and labors under the same difficulty.

Consequently it must be said absolutely that there is not one possible intellect for all men, but that there are many intellects, one for each man. And since the intellect is a certain power or capacity of the human soul, it is multiplied according as the substance of the soul itself is multiplied; which multiplication can be considered in the following way. For if a thing having a certain common character is multiplied materially, it must be multiplied numerically while remaining specifically the same. For instance, flesh and bones belong to the very notion of animal. Hence the distinction between animals, which is based on individual bodily differences, makes them numerically, but not specifically, diverse. Moreover, it is clear from what was said above (Arts. 1 and 1) that the human soul by its very nature is capable of union with the human body, because the human soul is not a complete species in itself, but acquires the completion of its species in the composite itself. Hence the fact that the soul is capable of being united to this or to that body, multiplies the soul numerically, not specifically; just as this whiteness differs numerically from that, because it belongs to this or that subject. But the human soul differs from other forms in this way, that its act of existing does not depend on the body. Nor does this individuated act of existing which it has, depend on the body; for inasmuch as a thing is one, it is undivided in itself and distinct from other things.

Answers to objections.

1. Truth is the conformity of the intellect with the thing [known]. Therefore there is one truth which different men understand, inasmuch as their conceptions conform to the same known object.

2. Augustine acknowledges that his position is ridiculous, not if he says many souls, but if he says many without qualification, so that souls would be many both numerically and specifically.

3. The possible intellect is not multiplied among different individuals because of any formal diversity, but because the substance of the soul, of which the intellect is a power, has a multiple existence.

4. It is not necessary for the intellect as such (commune) to completely lack what it understands, but only the intellect in potency; just as every recipient lacks the nature received. Hence, if there exists an intellect which is Act alone (as the divine intellect is), it understands itself through itself. But the, possible intellect is said to be intelligible, just as other intelligible things are, because it understands itself through the intelligible species of other intelligible things. For it knows its operation with respect to an object, and acquires knowledge of itself through this operation.

5. The possible intellect must be understood to have nothing in common with any of the sensible natures from which it derives its intelligible species. However, one possible intellect is specifically the same as another.

6. Those things which exist apart from matter can differ from one another only specifically. Moreover, things which are specifically diverse belong to different grades [of being]. Hence they resemble numbers which differ specifically from one another as a result of the addition and subtraction of a unit. Consequently it follows, from the position of those who maintain that inferior beings are caused by superior ones, that in the case of beings existing in separation from matter there is multiplicity so far as cause and thing caused are concerned. But this position may not be held according to faith . Therefore the possible intellect is not a substance existing apart from matter. Hence the reason given does not support the argument.

7. The intelligible species through which the intellect understands formally, is present in the possible intellect of this and of that particular man, and for this reason it follows that there are many possible intellects. Nevertheless the quiddity (quod) known through such a species is one, if we consider this quiddity in relation to the thing known; because the universal which is understood by both of these men is the same in all the things [of which it is the universal representation]. Moreover, the fact that what is one-in-all [i.e., the universal] can be understood through species multiplied among diverse individuals, is made possible by the immateriality of these species. For species represent a thing without the material individuating conditions which give the simple specific nature a multiple existence among diverse things.

8. According to the Platonists the reason why something is understood as a one-in-many [i.e., universally], is not to be attributed to the intellect, but to the thing. They argue that, because our intellect knows a thing as a one-in-many, it would apparently be empty of any real content unless there were one real nature shared by many individuals. For in that case the intellect would have in itself nothing corresponding to this one-in-many in reality. Hence the Platonists felt obliged to posit Ideas, by participation in which both natural things are given their specific nature, and our intellects made cognizant of universals. But according to Aristotle, the fact that the intellect understands a one-in-many in abstraction from individuating principles, is to be attributed to the intellect itself. And though nothing abstract exists in reality, the intellect is not void of any real content, nor is it misrepresentative of things as they are; because, of those things which necessarily exist together, one can be truly understood or named without another being understood or named. But it cannot be truly understood or said of things existing in this way, that one exists without the other. Thus whatever exists in an individual which pertains to the nature of its species, and in respect of which it is like other things, can be known and spoken of truly without taking into consideration its individuating principles, which distinguish it from all other individuals [of the same species]. Consequently, by its abstractive power the intellect makes this universal unity itself, not as though it were a unity existing in things themselves, but as an immaterial representation of them.

9. The intellect is the place of species because it contains them. Hence it does not follow that there is one possible intellect for all men, but that it is one and common to the whole species.

10. Sense does not receive species without an organ, and therefore sense is not said to be the place of species in the same manner as the intellect is.

11. The possible intellect can be said to operate everywhere, not because it actually does so, but because its intellectual operation comprehends things which exist everywhere.

12. Although the possible intellect has no determinate matter, the substance of the soul, of which the intellect is a power, has a determinate matter. However it does not have matter as a constituent part, but as something in which it exists.

13. The individuating principles of all forms are not of the very essence of these forms. This is true only in the case of things composed of matter and form.

14. The Prime Mover of the heavens exists in complete separation from matter. Therefore He cannot be multiplied numerically in any way whatever. However, the same thing is not true of the human soul.

15. Souls existing apart from bodies do not differ specifically, but numerically, because they are capable of being united to this or to that particular body.

16. Although the possible intellect is separated from the body so far, as its operation is concerned, nevertheless it is a power of the soul which is the act of the body.

17. Something is potentially known, not because it is individual, but because it is material. Hence the intelligible species that are received in the intellect immaterially are actually known, even though they are individuated. Furthermore, the same [incongruity set forth in this objection] follows logically from the position of those who maintain that there is one possible intellect for all men. For if there is one possible intellect existing as a separate substance, it must be an individual thing. This is the argument that Aristotle employs against Plato’s Ideas. The intelligible species in the intellect would be individuated for the same reason, and would differ in diverse separate intellects as well, because every intelligence is filled with intelligible forms.

18. A phantasm moves the intellect so far as the possible intellect is made actually cognizant by the power of the agent intellect to which the possible intellect is related as potency is to act. This is the way in which the intellect has something in common with a phantasm.

19. Although the soul’s act of existing does not depend on the body, nevertheless it is related by its very nature to the body for the completion of its species.

2o. Although the human soul does not contain matter as an intrinsic part of itself, it is still the form of the body. Therefore its nature involves relationship with the body.

2 1. Although the possible intellect transcends the body, it does not transcend the entire substance of the soul, which has a multiple existence because it inhabits diverse bodies.

22. This argument would be true if the body were united to the soul in such a way as to embrace the whole essence and power of the soul, for then whatever exists in the soul would nece ssarily be material. But this is not the case as was shown above, and therefore this argument is not legitimate.

ARTICLE 4

WHETHER IT IS NECESSARY TO ADMIT THAT AN AGENT INTELLECT EXISTS

[Summa theol., I, q. 79, a. 3; q. 54, a.4; Contra Gentiles, II, 77; De spir. creat., a.9; Compend. theol., chap. 83; Comm. in De anima, III, lect. 10.]

In the fourth article we examine this question: Whether it is necessary to admit that an agent intellect exists.

Objections.

1. It seems unnecessary to admit that an agent intellect exists. For whatever can be accomplished in nature by one thing is not done by many. Now a man can understand quite well by means of one intellect, namely, the possible intellect. Therefore it is unnecessary to admit that an agent intellect exists. The minor proposition is proved thus: powers that are rooted in one and the same essence of the soul influence one another. It is for this reason that an impression is made on the imagination as a result of a change in the [external] sense powers, for the imagination is moved [i.e., actuated or informed] when the external senses are actuated, as is said in the De anima [III, 3, 429a 1]. Therefore, if the possible intellect belongs to our soul, and is not a separate substance, as we have explained above (Art. 2), it must belong to the same essence of the soul as the imagination does. Hence a change in the imagination flows into the possible intellect, and thus it is unnecessary to admit that an agent intellect exists which makes phantasms intelligible by abstracting [species] from the phantasms themselves.

2. Further, touch and sight are different powers. Now in the case of one who is [born] blind, it happens that the imagination is moved to imagine something that belongs to the sense of sight from a change produced in the imagination by the sense of touch, and this occurs because sight and touch are rooted in one and the same essence of the soul. Therefore, if the possible intellect is a certain power of the soul, then, for a similar reason, an impression will be produced in the possible intellect from a change in the imagination. Thus it is unnecessary to admit that an agent intellect exists.

3. Further, an agent intellect is held to exist in order that the potentially intelligible may be made actually intelligible. Moreover, some things are made actually intelligible by being abstracted from matter and from material conditions. Thus an agent intellect is held to exist in order that intelligible species may be abstracted from matter. However, this can be accomplished without an agent intellect, for, since the possible intellect is immaterial, it must receive things in an immaterial way, because whatever is received is in the recipient according to the mode of the recipient. Therefore it is unnecessary to admit that an agent intellect exists.

4. Further, in the De anima [III, 5, 430a 15],Aristotle compares the agent intellect to light. But light is necessary for sight only inasmuch as it makes the medium (diaphanus) to be actually luminous; for color is visible in virtue of its own nature, and moves the medium which is actually luminous, as is explained in the De anima [II, 7, 418a 26; 418b 27]. However, the agent intellect is not required in order to prepare the possible intellect for the reception of species, because the possible intellect is in potency to intelligible species by its very nature. Therefore it is unnecessary to maintain that an agent intellect exists.

5. Further, just as our intellect is related to intelligible things, so are our senses related to sensible things. Now sensible things require no agent [sense] in order that they may move the senses, yet sensible things are present with an immaterial mode of existence, both in the senses, which are receptive of sensible things without matter, as is said in the De anima [III, 8, 431b 25], as well as in the medium [e.g., the air], which receives the species of sensible things in an immaterial way. This is evident from the very fact that the species of contrary qualities, such as white and black, are received in the same part of the medium. Therefore neither do intelligible things require an agent intellect.

6. Further, in order for something in potency to be made actual in the case of natural things, something actual belonging to the same genus is sufficient; for example, in the case of matter, whatever is ablaze potentially is set ablaze actually by fire, which is in act. Therefore, for our intellect, which is in potency, to be actuated, nothing more is required than the intellect in act, either of the knower himself, as when we proceed from a knowledge of principles to a knowledge of conclusions, or of someone else, as when someone learns from a teacher. Consequently it seems unnecessary to maintain that an agent intellect exists.

7. Further, an agent intellect is held to exist in order that it may illuminate our phantasms, just as the light of the sun illuminates colors. But the divine light, “which illuminates every man coming into this world” (John 1:9), suffices for our illumination. Consequently it is unnecessary to maintain that an agent intellect exists.

8. Further, intellection is the activity of an intellect. Therefore, if there are two intellects, that is, an agent and a possible intellect, the intellection of one and the same man will be twofold. This is incongruous.

9. Further, it is seen that an intelligible species perfects our intellect. Therefore, if there are two intellects, namely, a possible and an agent intellect, there are two distinct acts of intellection. This seems unnecessary.

On the contrary, in the De anima [III, 5, 430a 10], Aristotle concludes that, since in every nature there is something active and something potential, these two things must be found within the soul itself, and one of these is the agent intellect, the other the possible intellect.

I answer: We must admit that an agent intellect exists. To make this evident we must observe that, since the possible intellect is in potency to intelligibles, the intelligibles themselves must move [i.e., actuate] the possible intellect. But that which is non-existent cannot move anything. Moreover, the intelligible as such, that which the possible intellect understands, does not exist in reality; “ for our possible intellect understands something as though it were a one-in-many and common to many [i.e., universal]. However, such an entity is not found subsisting in reality, as Aristotle proves in the Metaphysics [VII, 13, 1039a 15]. Therefore, if the possible intellect has to be moved by an intelligible, this intelligible must be produced by an intellective power. And since it is impossible for anything in potency, in a certain respect, to actuate itself, we must admit that an agent intellect exists, in addition to the possible intellect, and that this agent intellect causes the actual intelligibles which actuate the possible intellect. Moreover, it produces these intelligibles by abstracting them from matter and from material conditions which are the principles of individuation. And since the nature as such of the species does not possess these principles by which the.nature is given a multiple existence among different things, because individuating principles of this sort are distinct from the nature itself, the intellect will be able to receive this nature apart from all material conditions, and consequently will receive it as a unity [i.e., as a one-in-many]. For the same reason the intellect receives the nature of a genus by abstracting from specific differences, so that it is a one-in-many and common to many species.

However, if universals subsisted in reality in virtue of themselves, as the Platonists maintained, it would not be necessary to admit than an agent intellect exists; because things which are intelligible in virtue of their own nature move the possible intellect. Therefore it appears that Aristotle was led by this necessity to posit an agent intellect, because he did not agree with the opinion of Plato on the question of Ideas. Nevertheless there are some subsistent things in the real order which are actual intelligibles in virtue of themselves; the immaterial substances, for instance, are of this nature (see Art. 7). However, the possible intellect cannot attain a knowledge of these immediately, but acquires its knowledge of them through what it abstracts from material and sensible things (see Art. 16).

Answers to objections.

1. Our act of intellection cannot be accomplished by the possible intellect alone, for the possible intellect can understand only when it is moved by an intelligible, and this intelligible, since it does not already exist in the real order, must be produced by the agent intellect. Moreover, it is true that two powers, which are rooted in one and the same substance of the soul, do influence each other; but this influence can be understood to occur in two ways: first, inasmuch as one power is hindered or totally prevented from performing its operation when another power operates intensely; however, this has no bearing on the problem; secondly, inasmuch as one power is moved by another, as the imagination is moved by the [external] senses. Now this is possible because the forms in the imagination and those in the external senses are generically the same, for all are individual forms. Therefore the forms which are in the external senses can impress those forms which exist in the imagination by moving the imagination, because they are similar to these forms. However, the forms in the imagination, since they represent things as individuals, cannot cause intelligible forms, because these are universal.

2. The species received in the imagination from the sense of touch are not enough to cause the imagination to produce forms belonging to the sense of sight, unless forms previously received by the sense of sight are stored up in the repertory of memory or imagination. For one who is born blind cannot imagine color by any other kind of sensible species whatever.

3. The condition of the recipient cannot cause a species which has been received, to be transferred from one genus to another; however, it can alter a received species of, the same genus according to some mode of being. Hence, since a universal species and a particular species differ generically, it follows that the cognitive activity of the possible intellect alone is not enough to give the particular species in the imagination the universality which they possess in the intellect, but that an agent intellect is required to do this.

4. There are two opinions concerning light, as the Commentator points out in the De anima [II, 67]. For some said that light is necessary for sight inasmuch as it gives to colors the power of moving the sense of sight, as if color were not visible of itself, but only through light. But this seems to contradict Aristotle, since he points out in the De anima [II, 7, 418a 29]. that color is visible in virtue of itself, and this would not be the case if it were made visible by light alone. For this reason others offer a different and more acceptable explanation, namely, that light is necessary for sight inasmuch as it perfects the medium, making it to be actually luminous. Wherefore the Philosopher says in the De anima [II, 7, 418a 33] that color has the power of moving what is actually luminous. Nor is this position rendered untenable by the fact that someone in the dark sees things which are in the light, but not vice versa. For this occurs because the medium, which surrounds a visible thing, must be illuminated in order that the medium may receive the visible species; and this remains visible as long as the act of light continues to illuminate the medium, although it illuminates it more perfectly the nearer it is, and more weakly the farther it is away. Consequently the comparison between light and the agent intellect does not hold in all respects, because the agent intellect is necessary for this reason, that it may make the potentially intelligible to be actually intelligible. Aristotle pointed this out in the De anima [III, 5, 430a 15] when he said that the agent intellect is like light in some respects.

5. Since a sensible is something particular, it does not impress a species of a higher genus, either on the sense or on the medium, because the species existing in the medium and in the sense is a particular and nothing more. The possible intellect, however, receives species of a higher genus than those present in the imagination; because the possible intellect receives universal species, whereas the imagination contains only particular species. Therefore we require an agent intellect in the case of intelligible things, but need no additional agent power in the case of sensible things. Indeed, all the sentient powers are passive powers.

6. The possible intellect in act is not sufficient to, cause knowledge in us unless an agent intellect is presupposed. For if we speak of the intellect in act of one who is learning, it so happens that his possible intellect is in potency with respect to some things, and in act with respect to others; and his intellect can be put into act, so far as the things to which it is in potency are concerned, by the things that are already actually known; just as one is made to be actually knowing conclusions,, which were previously known only potentially, by actually knowing principles. However, the possible intellect can be actually knowing principles only through the activity of the agent intellect; for our knowledge of principles is received from sensible things, as is stated at the end of the Posterior Analytics [II, 19, 100a 10]. Moreover, intelligibles can be derived from sensible things only by the abstractive activity of the agent intellect. Thus it is evident that the intellect in act with respect to principles, does not suffice to move the possible intellect from potentiality to act without the agent intellect. Indeed, in this actuating of the possible intellect, the agent intellect acts like an artisan and the principles of demonstration like tools. However, if we speak of the intellect in act of the teacher, it is evident that when the teacher causes knowledge in one who is learning, he does not act as an interior agent, but as an external administrator, just as in the production of health a physician acts as an external administrator, whereas the nature of the patient acts as an interior agent.

7. Just as real things of any kind require proper active principles, even though God is the first and universal agent, so too does man require a proper intellective light, even though God is the First Light illuminating all men in common.

8. There is a proper activity for each one of the two intellects, that is, the possible intellect and the agent intellect. For the activity of the possible intellect consists in receiving intelligibles, whereas that of the agent intellect consists in abstracting them. Nor does it follow that there are two distinct acts of understanding in a man, because it is necessary that the activities of both intellects concur to produce one act of understanding.

9. The same intelligible species is related to the agent intellect and to the possible intellect. However, it is related to the possible intellect as a recipient, and to the agent intellect as the one producing species of this sort by abstraction.

ARTICLE 5

WHETHER THERE IS ONE SEPARATELY EXISTING AGENT INTELLECT FOR ALL MEN

[Summa theol., I. q.79. a.4, 5; Contra Gentiles, II, 76, 78; Sent., II dist. 17, q.2, a. 1; De spir. creat., a. 10; Comm. in De anima, III, lect. 10; Compend. theol., chap. 86.]

In the fifth article we examine this question: Whether there is one separately existing agent intellect for all men.

Objections.

1. It seems that there is. Because the Philosopher says, in the De anima [III, 5, 430a 22], that the agent intellect is not at one time knowing and at another not. But nothing of this nature exists in us. Hence the agent intellect exists apart from men, and therefore is one and the same for all men.

2. Further, nothing can be in potency and in act with respect to the same thing simultaneously. Now the possible intellect is in potency with respect to every intelligible species. However, the agent intellect is in act with respect to them, because it is the act [producing] them. Therefore it seems that the possible and agent intellect cannot be rooted in the same substance of the soul. Hence, since the possible intellect is rooted in the essence of the soul, as is evident from the preceding articles (Arts. 1, 2 and 2), the agent intellect will exist apart from the soul.

3. But it might be said that the possible intellect is in potency to intelligible species, and the agent intellect in act with respect to them according to different modes of existence.

On the other hand, the possible intellect is not in potency to intelligible species when it possesses them, because then it is actuated by them. Hence it is in potency to intelligible species as existing in phantasms. But the agent intellect is related to such species as the act [which produces them], because it makes them actually intelligible by abstraction. Hence the possible intellect is in potency to intelligible species with respect to that mode of existence according to which the agent intellect is related to them as the one producing them.

4. Further, in the De anima [III, 5, 430a 17] the Philosopher attributed to the agent intellect certain properties which seem to belong only to separate substances. For he says that “this [i.e., the intellect] alone is perpetual, incorruptible, and separate.” Therefore its seems that the agent intellect is a separate substance.

5. Further, the intellect does not depend on any bodily disposition, because it is not united to a bodily organ. But our faculty of understanding is affected by different physical dispositions .5 Consequently this [intellective] faculty of ours is not identical with this intellect which is present in us; so it seems that the agent intellect has a separate existence.

6. Further, in order to have activity, an agent and a patient alone are necessary. Therefore, if the possible intellect, which is the patient in cognition, is a part of our substantial principle, as was previously shown (Art. 3), and the agent intellect is also a part of our soul, it seems that we possess within ourselves everything necessary in order that we may be able to understand. Hence we require nothing more in order to be able to do so. But this is clearly false. For we need the senses through which we acquire the experience necessary for cognition. This is the reason why a man deprived of a sense, for instance, sight, lacks a knowledge of colors. In order to learn we also require instruction, which is given by a teacher. And above all we stand in need of the illumination given by God, for it is said: “It was the true Light that enlightens every man who comes into this world” (John 1:9).

7. Further, the agent intellect is related to intelligible objects as light is to visible objects, as is evident in the De anima [ibid., 430a 14]. But one light existing apart from things, that is, the sun, suffices to make all things actually visible. Consequently one [intellectual] light existing apart from men, suffices to make everything actually intelligible. Hence it is unnecessary to maintain that an agent intellect exists in each one of us.

8. Further, the agent intellect is similar to an art, as is clear in the De anima [ibid., 430a 15] But an art is a principle separate from the objects produced by it. Therefore the agent intellect is also a separate principle.

9. The perfection of a nature consists in being like its agent, for a thing generated is perfect when it resembles the thing producing it. A thing produced by art is also perfect when it resembles the form in the mind of the artisan. Therefore, if the agent intellect belongs to our soul, the ultimate perfection and happiness of our soul will be found in some part of the soul itself; which is evidently false. For in that case the ultimate happiness of the soul would be the enjoyment of itself. Consequently the agent intellect is not something that exists within ourselves.

10. Further, an agent is nobler than a patient, as is pointed out in the De anima [ibid., 430a 17]. Therefore, if the possible intellect is separated in some measure from the body, the agent intellect will be separated to an even greater degree; and we see that this can be so, only if the agent intellect is held to bp completely separated from the substance of the soul.

On the contrary, there is this statement in the De anima [ibid., 430a 10] that since there is something in every nature like matter [i.e., potential] and something which is productive [i.e., active], these two distinct elements must likewise be found within the soul. The possible intellect corresponds to one of these, the agent intellect to the other. Therefore both the possible and agent intellect belong to the soul.

Further, the operation of the agent intellect is to abstract intelligible species from phantasms. Now it is certain that this operation is not continually taking place in us. However, there would be no reason why such abstraction should sometimes occur and sometimes not, as is seen to be the case if the agent intellect were a separate substance. Consequently the agent intellect is not a separate substance.

I answer: It is obviously more reasonable to maintain that the agent intellect is unique and separate, than to hold that this is true of the possible intellect. For the possible intellect, in virtue of which we are capable of understanding, is sometimes in potency and sometimes in act. The agent intellect, on the other hand, is that which makes us actually understanding. Now an agent exists in separation from the things which it brings into actuality, but obviously whatever makes a thing potential is wholly within that thing.

For this reason many maintained that the agent intellect is a separate substance, and that the possible intellect is a part of our soul. Furthermore they held that this agent intellect is a specific kind of separate substance, which they call an intelligence. They held that it is related to our souls, and to the entire sphere of active and passive qualities, as superior separate substances (which they also call intelligences) are related to the souls of the celestial bodies (for they considered these to be animated), and to the celestial bodies themselves. Hence they maintained that, as superior bodies receive their motion from these separate substances, and the souls of the heavenly bodies .their intelligible perfections, so also do all the bodies of this inferior sphere receive their forms and movements from the separate agent intellect, while our soul receives its intelligible perfections from it. But because the Catholic Faith maintains that God is the agent operating in our souls and not some separate substance in nature, some Catholics asserted that the agent intellect is God himself, who is “the true Light that enlightens every man who comes into this world” (John 1: 9).

But this position, if anyone examines it carefully, is seen to be implausible, because the superior substances are related to our souls as celestial bodies are to inferior bodies. For, as the powers of superior bodies are certain universal active principles in relation to inferior bodies, so also are the divine power and the powers of different secondary substances (if the latter do influence us in any way) related to our souls as universal active principles.

However, we see that there must exist in addition to the universal active principles of the celestial bodies, certain particular active principles which are powers of inferior bodies, limited to the proper operation of each and every one of them. This is particularly necessary in the case of perfect animals, because certain imperfect animals are found, for whose production the power of a celestial body suffices, as is evident in the case of animals generated from decomposed matter.” However, in the generation of perfect animals a special power is also required in addition to the celestial power, and this power is present in the seed. Therefore, since intellectual operation is the most perfect thing existing in the entire order of inferior bodies, we need in addition to universal active principles (namely, the power of God enlightening us, or the powers of any other separate substance) an active principle existing within us by which we are enabled to understand actually. This power is the agent intellect.

We must also consider this, that, if the agent intellect is held to exist as a separate substance along with God, a consequence repugnant to our faith will follow: namely, that our ultimate perfection and happiness consists not in a certain union of our soul with God, as the Gospel teaches, saying. “This is life eternal, that you may know the true God” (John 17:3), but with some other separate substance. For it is evident that man’s ultimate beatitude or happiness depends upon his noblest operation, intellection, which operation, in order to be fully completed, requires the union of our [possible] intellect with its active principle. For, indeed, anything passive in any way whatever is perfected [i.e., fully actuated] only when joined with the proper active principle which is the cause of its perfection. Therefore those maintaining that the agent intellect is a substance existing apart from matter, say that man’s ultimate happiness consists in being able to know the agent intellect.

Moreover, if we give the matter further careful consideration, we will find that the agent intellect cannot be a separate substance for the same reason that the possible intellect cannot be, as was shown above (Arts. 1-3). For, as the operation of the possible intellect consists in receiving intelligible [species], so also does the proper operation of the agent intellect consist in abstracting them, for it makes them actually intelligible in this way. Now we experience both of these operations in ourselves, because we receive our intelligible species, and abstract them as well. However, in anything that operates there must be some formal principle whereby it operates formally, because a thing cannot operate formally through something that possesses existence distinct from itself. But, although the motive principle of an activity [i.e., an efficient cause] is separate from the thing which it causes, nevertheless there must be some intrinsic principle whereby a thing operates formally, whether it be a form or some sort of impression. Therefore there must exist within us a formal principle through which we receive intelligible species, and one whereby we abstract them. These principles are called the possible and the agent intellect respectively. Consequently each exists within us. Moreover, [the formal intrinsic existence in us of the agent intellect] is not accounted for simply by the fact that the action of the agent intellect, namely, the abstracting of intelligible species, is carried out through phantasms illumined in us by its action. For every object produced by art is the effect of the action of an artificer, the agent intellect being related to the phantasms illumined by it as an artificer is to the things made by his art.

Now it is not difficult to see how both of these can be present in one and the same substance of the soul: that is, the possible intellect, which is in potency to all intelligible objects, and the agent intellect which makes them actually intelligible; because it is not impossible for a thing to be in potency and in act with respect to one and the same thing in different ways. Therefore, if we consider the phantasms themselves in relation to the human soul, in one respect they are found to be in potency, inasmuch as they are not abstracted from individuating conditions, although capable of being abstracted. In another respect they are found to be in act in relation to the soul, namely, inasmuch as they are [sensible] likenesses of determinate things. Therefore potentiality with respect to phantasms must be found within our soul so far as these phantasms are representative of determinate things. This belongs to the possible intellect which is, by its very nature, in potency to all intelligible objects, but is actuated by this or that object through species abstracted from phantasms. Our soul must also possess some active immaterial power which abstracts the phantasms themselves from material individuating conditions. This belongs to the agent intellect, so that it is, as it were, a power participated from the superior substance, God. Hence the Philosopher says [De Anima, III, 5, 430a 14] that the agent intellect is like a certain habit and light. In the Psalms it is also said: “The light of Thy countenance is signed upon us, O Lord” (Ps. 4:7). Something resembling this in a certain degree is apparent, in animals who see by night. The pupils of their eyes are in potency to every color inasmuch as they have no one determinate color actually, but make colors actually visible in some way by means of a certain innate light.

Indeed, some men thought that the agent intellect does not differ from our habitus of indemonstrable principles. But this cannot be the case, because we certainly know indemonstrable principles by abstracting them from singulars, as the Philosopher teaches in the Posterior Analytics [II, 19, 100b 4]. Consequently the agent intellect must exist prior to the habitus of first indemonstrable principles in order to be the cause of it. Indeed, the principles themselves are related to the agent intellect as certain of its instruments, because the intellect makes things actually intelligible by means of such principles.

Answers to objections.

1. The Philosopher’s statement that “the intellect is not at one time knowing and at another not” [De Anima, III, 5, 430a 22] is not understood of the agent intellect, but of the intellect-in-act. For after Aristotle had determined the role of the possible and agent intellect, he had to determine the role of the intellect-in-act. He first distinguishes it in relation to the possible intellect, because the possible intellect and the thing known are not one and the same. However, the intellect or science-in-act is the same as the thing actually known. Aristotle had said the same thing about sense, namely, that sense and what is potentially sensible differ from each other, but that sense and what is actually sensed are one and the same. Secondly, he shows how the possible intellect is related to the intellect-in-act, because in one and the same individual, intellect in potency precedes intellect-in-act. However, it does not precede it absolutely, for he very often uses this manner of speaking concerning things that pass from potentiality to actuality. Then he makes the statement quoted above, in which he shows the difference between the possible intellect and the intellect-in-act, because the possible intellect sometimes understands and sometimes does not, which cannot be said of the intellect-in-act. He points out a similar difference, in the Physics [III, 1, 201a 20] between causes in potency and causes in act.

2. The substance of the soul is in potency and in act with respect to the same phantasms, but not in the same way, as was shown above.

3. The possible intellect is in potency with respect to intelligible species, and the agent intellect in act with respect to them, in relation to the existence which such species have in phantasms; but for different reasons, as was shown.

4. Those words of the Philosopher, “This alone is separate, immortal, and perpetual,” cannot be understood to apply to the agent intellect. For Aristotle had also previously stated that the possible intellect is separate. However, they must be understood to apply to the intellect-in-act in view of the context in which they occur, as was shown above (Ans. obj. 1). For intellect-in-act embraces both the possible intellect and the agent intellect. And only that part of the soul which contains the agent and possible intellects is separate, perpetual, and immortal. For the other parts of the soul have no existence without the body.

5. Diversity of dispositions causes the intellective faculty to understand more or less perfectly b