Article 3 — Whether there is one potential intellect, or intellective soul, for all men

Third, it is asked whether there is one potential intellect, or intellective soul, for all men. (Parallel texts: ST I.76.2; SCG II.59, 73, 75; In I Sent., d. 8, q. 5, a. 2, ad 6; In II Sent., d. 17, q. 2, a. 1; Commentary on Aristotle’s On the Soul, bk. 3, lect. 7‒8; On Spiritual Creatures, a. 9; On the Unity of the Intellect, cc. 4‒5; Compendium theologiae, bk. 1, ch. 85. On the translation of the term intellectus possibilis, see the note in the respondeo of q. 2 above.)

Obj. 1: It seems that there is. For a perfection is proportioned to what is perfectible. (Cf. SCG II.79.) But truth is the perfection of the intellect, for truth is the good of the intellect, as the Philosopher says in Ethics 6. (Aristotle, Nicomachean Ethics, 6.2, 1139a27–30; 1139b11; Aquinas, Commentary on the Nicomachean Ethics, bk. 4, lect. 2.) Therefore, since truth, which all men understand, is one, it seems that there is one potential intellect for all men. (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 2.)

Obj. 2: Further, in the book The Measure of the Soul, Augustine says, 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. (Augustine, The Measure of the Soul (De quantitate animae), ch. 32, para. 69 (CSEL 89:217; PL 32:1073).) Therefore, the existence of many souls, one for each man, seems to be ridiculous.

Obj. 3: Further, things that differ from each other differ because of the determinate nature which each possesses. But the potential intellect is in potency to all forms, having none actually. Consequently, the potential intellect in one man cannot differ from that in another, and thus there cannot be many potential intellects, one for each man. (Cf. Aquinas, In II Sent., d. 17, q. 2, a. 1, obj. 4.)

Obj. 4: Further, the potential intellect totally lacks everything that it knows because, prior to actual understanding, it possesses none of the things that it is cognizant of, as is said in On the Soul 3. (Aristotle, On the Soul 3.4, 429a18–24.) But, as is said in the same book, it completely lacks any nature of its own, (Aristotle, On the Soul 3.4, 430a2–3; cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 15.) and thus it cannot have a multiple existence among different individuals.

Obj. 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 potential intellect does not have anything in common with other things, as is said in On the Soul 3. (Aristotle, On the Soul 3.4, 429a23; 429b23–24; 1.2, 405b20–21; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 3, n. 720; bk. 3, lect. 1, n. 677; bk. 1, lect. 5, n. 66.) Therefore, the potential intellect in one man cannot differ from that in another, and thus there cannot be many potential intellects, one for each man.

Obj. 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. (Moses Maimonides (1135‒1205 AD), The Guide for the Perplexed, bk. 2, ch. 1, proposition 16.) But the intellect or soul of one man is not the cause of the intellect or soul of another. Therefore, since the potential intellect is separate, as is said in On the Soul 3, there will not be many potential intellects, one for each man. (Aristotle, On the Soul 3.4, 429a24; 429b5.)

Obj. 7: Further, the Philosopher says in On the Soul 3 that the intellect and what is understood are one and the same. (Aristotle, On the Soul 3.4, 430a3–4; 3.5, 430a19–20; 3.7, 431a1; 3.8, 431b21; cf. 3.2, 425b25–26; 426a15.) But what is understood is one and the same for all men. Therefore, there is one potential intellect for all men. (Cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 5; Aquinas, On Spiritual Creatures, a. 9, obj. 15 and ad 6; On the Unity of the Intellect, ch. 5.)

Obj. 8: Further, that which is understood is a universal, which is a one-in-many. 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. (Cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 9; Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 12.) Therefore, the form derives this unity from the intellect. Consequently, there is one intellect for all men. (Above: q. 2, obj. 6.)

Obj. 9: Further, the Philosopher says in On the Soul 3 that the soul is the place of species. (Aristotle, On the Soul 3.4, 429a26–28.) But place is common to different things in place. Therefore, there are not many souls, one for each man.

Obj. 10: But it might be said that the soul is the place of species because it contains species. (See below: ad 9; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 1, n. 686.)

On the contrary, 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 On the Soul 3, that not every soul is the place of species, but only the intellective soul. (Aristotle, On the Soul 3.4, 429a26–28.)

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

Obj. 12: Further, whatever is limited to some one particular thing has a determinate matter, because the principle of individuation is matter. But the potential intellect does not have a determinate matter, as is proved in On the Soul 3. (Aristotle, On the Soul 3.4, 429a18–27; 3.8, 431b30.) Therefore, it is not found to exist in each particular man and thus is one for all men. (Cf. Aquinas, In II Sent., d. 17, q. 2, a. 1, obj. 1.)

Obj. 13: But it might be said that the potential intellect has matter in the thing in which it exists, namely, in the human body in which it is confined. (Cf. Aquinas, In II Sent., d. 17, q. 2, a. 1, ad 5; On Spiritual Creatures, a. 9, obj. 3.)

On the contrary, the principle of individuation should belong to the individuated essence. But the body is not an essential part of the potential intellect. Therefore, the potential intellect cannot be individuated by the body and consequently cannot have a multiple existence. (Cf. Aquinas, On Spiritual Creatures, a. 9, obj. 4; Aristotle, Metaphysics 7.10, 1035b29.)

Obj. 14: Further, the Philosopher says in On the Heavens 1 that if there were many worlds, there would be many first heavens. (Aristotle, On the Heavens 1.8, 276a18–b25; 1.9, 277b27–278b8; 279a8–11; Metaphysics 12.8, 1074a31–35; cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 5; Siger of Brabant (ca. 1240–1284 AD), Q. in tertium De anima, q. 9; De anima intellectiva, ch. 7; Aquinas, On Spiritual Creatures, a. 9, s.c. 3.) 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 potential intellects, one for each man, the potential intellect would be material, which is impossible.

Obj. 15: Further, if there were many potential intellects, one for each man, they would remain many when their bodies have corrupted. But then, since they could differ only as regards form, they would have to differ in species. Therefore, since potential intellects do not become different in species when their bodies have corrupted—because nothing is changed from one species into another unless it is corrupted (Cf. Aristotle, Physics 5.1, 225a17; Aquinas, Commentary on Aristotle’s Physics, bk. 5, lect. 2, n. 655.)—potential intellects were different in species 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. (Cf. Aquinas, In II Sent., d. 17, q. 2, a. 1, obj. 5; SCG II.80; Compendium theologiae, bk. 1, ch. 85; ST I.76.2, obj. 2; Commentary on the Nicomachean Ethics, bk. 1, lect. 13 and 15.)

Obj. 16: Further, whatever exists in separation from a body cannot be given a multiple existence by bodies. But the potential intellect is separate from the body, as the Philosopher proves in On the Soul 3. (Aristotle, On the Soul 3.5, 430a19; 3.4, 429a24–27; 429b5.) Therefore, the potential intellect can neither be multiplied nor individuated by bodies. Consequently, there are not many potential intellects, one for each man. (Cf. Aquinas, In II Sent., d. 17, q. 2, a. 1, obj. 1.)

Obj. 17: Further, if a potential 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 understood, for the universal, which is the proper object of understanding, must be abstracted from such forms. Therefore, the forms which are in the potential intellect will only be potentially intelligible, and thus the potential intellect will be unable to be actually understood, which is incongruous. (Cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 5; Aquinas, In II Sent., d. 17, q. 2, a. 1, obj. 3; SCG II.59; ST I.76.2, obj. 4; Compendium theologiae, bk. 1, ch. 85; On Spiritual Creatures, a. 9, obj. 13.)

Obj. 18: Further, an agent and patient, mover and thing moved, have something in common. Now a phantasm is related to the intellect existing in us as an agent to a patient, and as a mover to something moved. (Note that this position is not the position of Averroes; see Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 5, 18.) Therefore, the intellect existing in us has something in common with phantasms. (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 4.) But the potential intellect has nothing in common with the latter, as is pointed out in On the Soul 3. (Aristotle, On the Soul 3.4, 429b22–24.) Therefore, the potential intellect differs from the intellect which is present in us and so is not multiplied among diverse men.

Obj. 19: Further, a thing, inasmuch as it exists, is one. Therefore, neither its act of existing nor its unity depends on another. But the potential 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 potential intellect does not depend on the body and so neither does its multiplicity. Therefore, the potential intellect is not multiplied among different bodies. (That is, it is not multiplied in such a way that each man possesses his own potential intellect.)

Obj. 20: Further, the Philosopher says in Metaphysics 8 that in those things which are forms alone, (That is, those things not composed of matter and form.) the thing and its that-which-it-was-to-be, that is, the nature of its species, are one and the same. (Aristotle, Metaphysics 8.6, 1045a36–b7; 8.3, 1043b1; cf. Aquinas, On Spiritual Creatures, a. 9, obj. 2.) But the potential 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.

Obj. 21: Further, the soul has a multiple existence among different bodies only by being united thereto. But the potential intellect belongs to that part of the soul which transcends bodily union. Hence, the potential intellect does not have a multiple existence among diverse men.

Obj. 22: Further, if many human souls exist because of the multiplicity of bodies, and many potential intellects because of the multiplicity of souls, and since it is certain that there must be many intelligible species if there are many potential 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 potential intellect will not be actually intelligible objects, which is incongruous. Hence, there will not be many human souls and potential intellects, one in each man.

On the contrary (1), man understands by the potential intellect. For it is said in On the Soul 3 that the potential intellect is that by which the soul understands. (Aristotle, On the Soul 3.4, 429a23; 3.5, 430a15.) Consequently, if there is one potential intellect for all men, it follows that one man understands what another does, which is clearly false.

Furthermore (2), 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 that this question depends in a certain way on the preceding one. (Cf. SCG II.73; On the Unity of the Intellect, ch. 1.) For if the potential 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. (Cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 5.) For it is at once apparent that there cannot be one potential intellect for all men. It is, indeed, clear that the potential 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 potential intellect. This fact compels us to maintain that a potential 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 potential 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, namely, the phantasms themselves and the potential intellect. (Above: q. 2, resp.; cf. Aquinas, In II Sent., d. 17, q. 2, a. 1, resp.; SCG II.73; Compendium theologiae, bk. 1, ch. 85; ST I.76.1, resp.; On Spiritual Creatures, a. 2, resp.; On the Unity of the Intellect, ch. 3.) 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 potential 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. (Above: q. 2, resp.) For species are actually intelligible only by being abstracted from phantasms and by existing in the potential 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 sensitive soul as their subject, as these men claim. (Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 20; cf. SCG II.73.)

But an even greater difficulty faces those who maintain that there is one potential intellect for all men. For it is evident that the act of understanding has its origin in the potential intellect as the first principle whereby we understand, just as the operation of sensing has its origin in a sensitive power. And although it was shown above that, if the potential intellect exists apart from man, the act of understanding (which belongs to the potential intellect) cannot be the operation of this or that man, (Above: q. 2, resp.) nevertheless, from the hypothesis of one potential intellect for all men, it follows that this or that man understands by the potential intellect’s own act of understanding.

Yet an operation can be multiplied in only two ways: either on the side of the object, or on that of the principle operating. (Cf. Aquinas, Compendium theologiae, bk. 1, ch. 85; On Spiritual Creatures, a. 9; On the Unity of the Intellect, ch. 4.) A third way 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 potential intellect.

Therefore, if the potential 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 potential 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. (Cf. Aquinas, On Spiritual Creatures, a. 9, resp.; On the Unity of the Intellect, ch. 4.) Therefore, it is impossible for the potential 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 potential 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. (Cf. SCG II.73; ST I.76.2, resp.; On the Unity of the Intellect, ch. 4.)

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, namely, the intellect, is that whereby man is made to be this species; it cannot be the sensory soul, nor any other power of man. Therefore, if the potential intellect, existing as a separate substance, is one for all men, then all men are made to be the species that they are by one substance existing apart from them. This position is reminiscent of the doctrine of ideas, and labors under the same difficulty. (Cf. Aristotle, Metaphysics 1.9, 990a34–b8; 991a2–5; 991a27–b1; Aquinas, SCG II.73; ST I.76.1; On Spiritual Creatures, a. 9; On the Unity of the Intellect, ch. 3.)

Consequently, it must be said absolutely that there is not one potential 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. This multiplication can be considered in the following way: if a thing having a certain common character is multiplied materially, it must be multiplied numerically while remaining the same in species. For instance, flesh and bones belong to the very account of animal. Hence, the distinction between animals, which is based on individual bodily differences, makes them diverse in number, not in species.

Moreover, it is clear from what was said above (Above: qq. 1–2.) that the human soul, by its very account, 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. (Aquinas, On Spiritual Creatures, a. 3.) Hence, the fact that the soul is capable of being united to this or to that body multiplies the soul in number, not in species, just as this whiteness differs in number 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; (Cf. Aquinas, In I Sent., d. 8, q. 5, a. 2, ad 6; On the Power of God, q. 3, a. 10, ad 16; Avicenna, De anima, part 5, cc. 3–4.) for inasmuch as a thing is one, it is undivided in itself and distinct from other things. (Cf. Aristotle, Physics 3.7, 207b1; Aquinas, Commentary on Aristotle’s Physics, bk. 3, lect. 12, n. 392; bk. 7, lect. 9, n. 960.)

Reply Obj. 1: Truth is the conformity of the intellect with the thing known. (See Avicenna, Metaphysics, bk. 1, ch. 8 (Avicenna’s Metaphysics is itself a section of The Book of Healing [al-Shifa’]); cf. Aquinas, On Truth, q. 1, a. 1, resp.) Therefore, there is one truth which different men understand, inasmuch as their conceptions conform to the same known object.

Reply Obj. 2: Augustine acknowledges that the position is ridiculous not if he says many souls, but if he says many without qualification, so that souls would be many both according to number and according to species.

Reply Obj. 3: The potential 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.

Reply Obj. 4: It is not necessary for the intellect as such 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. (Aristotle, Metaphysics 12.9, 1074b33–34; cf. Aquinas, Commentary on Aristotle’s Metaphysics, bk. 12, lect. 11, nn. 2611–16.) But the potential intellect is said to be intelligible, just as other intelligible things are, because it understands itself through the intelligible species of other intelligible things. (Aristotle, On the Soul 3.4, 430a2–3.) For it knows its operation with respect to an object and acquires knowledge of itself through this operation. (Cf. Aristotle, On the Soul 1.1, 403a10–12; Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 2.)

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

Reply Obj. 6: Those things which exist apart from matter can differ from one another only in species. (Cf. Aquinas, On the Power of God, q. 3, a. 10, resp.) Moreover, things which are diverse in species belong to different grades of being. Hence, they resemble numbers, which differ from one another in species as a result of the addition and subtraction of a unit. (Cf. Aristotle, Metaphysics 8.3, 1043b33–1044a2.) 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. (Cf. Aquinas, In II Sent., d. 1, q. 1, a. 3; On Truth, q. 5, a. 9, resp.; SCG II.20–21, 42; On the Power of God, q. 3, a. 4, resp.; Compendium theologiae, bk. 1, ch. 70; ST I.45.5; I.90.3; Commentary on the Book of Causes, prop. 3.) But this position may not be held according to faith. (Cf. Genesis 1:1.) Therefore, the potential intellect is not a substance existing apart from matter. Hence, the reason given does not support the argument.

Reply Obj. 7: The intelligible species through which the intellect understands formally is present in the potential intellect of this and of that particular man, and for this reason it follows that there are many potential intellects. Nevertheless, the quiddity 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. Moreover, the fact that what is one-in-all 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. (Cf. Aquinas, Compendium theologiae, bk. 1, ch. 85.)

Reply Obj. 8: According to the Platonists the reason why something is understood as a one-in-many is not to be attributed to the intellect, but to the thing. (Aristotle, Metaphysics 1.6, 987b1–4; cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 5.) 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. (Cf. ST I.84.4; I.84.5, obj. 3.)

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. (Aristotle, On the Soul 3.4, 429b20–22; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 4; bk. 3, lect. 2.) 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. (Cf. ST I.85.1, ad 1; Commentary on Aristotle’s On the Soul, bk. 2, lect. 12; bk. 3, lect. 6.) 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. (Cf. Aristotle, Metaphysics 1.9, 990b7–13; 991a2; Posterior Analytics 1.11, 77a6; Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 1; bk. 2, lect. 12.)

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

Reply Obj. 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. (Cf. Aristotle, On the Soul 3.4, 429a24–27; Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 1.)

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

Reply Obj. 12: Although the potential 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.

Reply Obj. 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.

Reply Obj. 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.

Reply Obj. 15: Souls existing apart from bodies do not differ in species, but in number, because they are capable of being united to this or to that particular body. (Cf. Aquinas, In I Sent., d. 8, q. 5, a. 2, ad 6.)

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

Reply Obj. 17: Something is potentially known, not because it is individual, but because it is material. (Cf. ST I.76.2, ad 3; On the Unity of the Intellect, ch. 5.) Hence, the intelligible species that are received in the intellect immaterially are actually understood, 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 potential intellect for all men. For if there is one potential intellect existing as a separate substance, it must be an individual thing. This is the argument that Aristotle employs against Plato’s ideas. (Aristotle, Metaphysics 7.15, 1039b30–32; 1040a8–9; cf. ST I.76.2, ad 3; On the Unity of the Intellect, ch. 5.) 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. (Cf. The Book of Causes, proposition 9 [10].)

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

Reply Obj. 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. (Cf. Aquinas, Compendium theologiae, bk. 1, ch. 85.)

Reply Obj. 20: Although the human soul does not contain matter as an intrinsic part of itself, it is still the form of the body. Therefore, that-which-it-was-to-be involves relationship with the body. (Cf. Aquinas, Compendium theologiae, bk. 1, ch. 85.)

Reply Obj. 21: Although the potential intellect transcends the body, it does not transcend the entire substance of the soul, which has a multiple existence because it inhabits diverse bodies.

Reply Obj. 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 necessarily be material. But this is not the case as was shown above, and, therefore, this argument is not legitimate. (Aquinas, On Spiritual Creatures, a. 4.)