Article 10 — Whether the soul exists in the whole body and in each of its parts

Tenth, it is asked whether the soul exists in the whole body and in each of its parts. (Parallel texts: ST I.76.8; SCG II.72; In I Sent., d. 8, q. 5, a. 3; On Spiritual Creatures, a. 4; Commentary on Aristotle’s On the Soul, bk. 1, lect. 14; see also: Augustine, On the Trinity, bk. 7, ch. 7, para. 8 (CCSL 50:237; PL 42:928–29).)

Obj. 1: It seems that the soul does not. For the soul exists in the body as a perfection in something perfectible. But the thing capable of being perfected by the soul is an organic body because the soul is the actuality of a physical organic body having life potentially, as is stated in book 2 of On the Soul. (Aristotle, On the Soul 2.1, 412a27–28; 412b5–6; ST I.76.8, obj. 2; On Spiritual Creatures, a. 4, obj. 13; John of Rupella, Summa de anima, bk. 1, ch. 42 [XL].) Therefore, the soul exists only in an organic body. But each part of the body is not an organic body. Therefore, the soul does not exist in each part of the body. (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 14.)

Obj. 2: Further, a form is proportioned to a matter. (See above: q. 9, obj. 10.) But the soul as the form of the body is a certain simple essence. Therefore, a complex matter is not proportioned to the soul. But the diverse parts of the body, either of a man or of an animal, are certainly complex matter, because these parts differ greatly from one another. Therefore, the soul is not the form of each part of the body, and thus it does not exist in each part of the body.

Obj. 3: Further, no part of a whole exists in separation from the whole. Therefore, if the whole soul exists in one part of the body, no part of the soul can exist outside that part of the body. Therefore, it is impossible for the soul to exist in each part of the body.

Obj. 4: Further, the Philosopher says in the book On the Motion of Animals that the animal must be considered as similar to a state which is well governed by laws. For when order is once established in it, there is no further need of a separate monarch to preside over each particular work. (Cf. Aquinas, On the Motion of the Heart.) But each individual performs the task to which he is directed by the authority of the ruler, and these things are done continually in a customary manner. In animals, however, the same order results from their nature, and each part performs the proper work for which it has been constituted by nature. Hence, there is not a soul for each part, but one single principle of the body exists, and the different parts of the body live because they are connected to one another. Moreover, they perform the proper operation allotted to them by nature. (Aristotle, On the Motion of Animals 1.10, 703a29–b2; cf. Aquinas, SCG II.72; ST I.76.8, obj. 1; On Spiritual Creatures, a. 4, obj. 1.) Therefore, the soul does not exist in each part of the body, but only in one part.

Obj. 5: Further, the Philosopher says in Physics 8 that the mover of the heavens must occupy either the center or some sign of the circumference, since these two things are the principles of circular motion. (Aristotle, Physics 8.10, 267b6–9; cf. Aquinas, Commentary on Aristotle’s Physics, bk. 8, lect. 23, n. 1168; bk. 2, lect. 3, n. 164; Commentary on Boethius’s De Trinitate, q. 5, a. 3, ad 5.) Now he proves that it cannot occupy the center but must exist at the circumference, for the nearer things are to the circumference and the farther away from the center, the swifter is their motion. Therefore, similarly, the movement of the soul must exist in that part of the animal in which movement is most apparent. Now this part is the heart. Therefore, the soul exists only in the heart. (Cf. Aristotle, On the Motion of Animals 1.10, 703a5–16; Nemesius, On the Nature of Man, ch. 23; Avicenna, De anima, part 5, ch. 8; Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 14; bk. 2, lect. 18; SCG II.72.)

Obj. 6: Further, the Philosopher says in the book On Youth and Old Age that plants have a nutritive principle midway between their upper and lower parts. (Aristotle, On Youth and Old Age, ch. 2, 467b30–468a5; 468a20–23.) But upper and lower are found not only in plants, but in animals as well, and these also have a right and left side, a front and a back. Therefore, the principle of life, namely, the soul, exists in an animal in the midst of its particular parts. But this position is occupied by the heart. Therefore, the soul exists only in the heart.

Obj. 7: Further, every form existing in a whole and in each of its parts is predicated of the whole and of each of its parts, as is evident in the case of fire, for each part of fire is fire. However, each part of an animal is not an animal. Therefore, the soul does not exist in each part of the body. (Cf. Aquinas, On Spiritual Creatures, a. 4, obj. 2.)

Obj. 8: Further, the act of understanding belongs to a part of the soul. But this act is not present in any part of the body. Therefore, the whole soul does not exist in each part of the body.

Obj. 9: Further, the Philosopher says in book 2 of On the Soul that as the soul is related to the body, so also is a part of the soul related to a part of the body. (Aristotle, On the Soul 2.1, 412b22–25; cf. ST I.76.8, obj. 3.) Therefore, if the soul exists in the whole body, the whole soul will not exist in each part of the body, but a part of the soul only will exist in a part of the body.

Obj. 10: But it has been said that the Philosopher is speaking of the soul and of its parts inasmuch as it is a mover and not a form.

On the contrary, the Philosopher says in another place that if the eye were an animal, sight would be its soul. (Aristotle, On the Soul 2.1, 412b18–22.) But the soul is the form of an animal. Hence, in the body, part of the soul has the character of a form, so that the soul is not merely a mover.

Obj. 11: Further, the soul is the principle of life in an animal. Therefore, if the soul were in each part of the body, each part would receive life directly from the soul. Then one part would not depend on another for life, which is clearly false, for the other parts of the body depend on the heart for life. (Cf. ST I.76.8, obj. 5; On Spiritual Creatures, a. 4, obj. 8; Bonaventure, In I Sent., d. 8, P. 2, q. 3, s.c. 7.)

Obj. 12: Further, the soul is moved accidentally by the movement of the body in which it exists. (Cf. Aristotle, On the Soul 1.3, 407b5–10; 1.4, 408a30–33.) Similarly, it is at rest accidentally when the body in which it exists is at rest. However, it happens that when one part of a body is at rest, another is moved. Therefore, if the soul exists in each part of the body, the soul must be moved and at rest simultaneously, which is evidently impossible. (Cf. Aquinas, On Spiritual Creatures, a. 4, obj. 7.)

Obj. 13: Further, all powers of the soul are rooted in the essence of the soul. (Cf. Aquinas, On Spiritual Creatures, a. 4, ad 3.) Therefore, if the essence of the soul exists in each part of the body, each power of the soul must exist in each part of the body. This is obviously false, for the sense of hearing does not exist in the eye but in the ear alone, and similarly for the other powers. (Cf. ST I.76.8, obj. 4; On Spiritual Creatures, a. 4, obj. 3.)

Obj. 14: Further, whatever exists in another exists there according to the mode of the thing in which it exists. Therefore, if the soul exists in the body, it must exist there in a manner proper to the body. But it is proper to a body that no part of it may exist where another part exists. Therefore, where one part of the soul exists, another does not exist; and thus, the whole soul does not exist in each part of the body.

Obj. 15: Further, certain imperfect animals, called ring-worms, (Cf. Aristotle, On the Soul 1.5, 411b19–22; 2.2, 413b20; Averroes, Commentary on Aristotle’s On the Soul, bk. 1, comm. 93; bk. 2, comm. 20.) continue to live after they have been dissected, because a soul exists in each part of the body after its dissection. But man and the other perfect animals do not live after they have been dissected. Consequently, in them the soul does not exist in each part of the body.

Obj. 16: Further, as a man and an animal are certain wholes composed of different parts, so also is a house. But the form of a house does not exist in each of its parts but in the whole. Therefore, the whole soul, which is the form of the animal, does not exist in each part of the animal but in the whole.

Obj. 17: Further, the soul as a form gives to the body its act of existing. However, the soul is the form of the body through its essence, which is simple. (See above: q. 6.) Therefore, the simple essence of the soul gives to the body its act of existing. But only one thing comes naturally from something that is one. (Avicenna, Metaphysics, bk. 9, ch. 4; cf. Averroes, Commentary on Aristotle’s Metaphysics, bk. 12, comm. 44; Aquinas, On the Power of God, q. 3, a. 16, ad 1, ad 11.) Therefore, if the soul as a form were in each part of the body, it would follow that it would give existence uniformly to each part of the body.

Obj. 18: Further, a form is united to matter more intimately than a thing in place is united to its place. But a thing existing in one place cannot exist in different places simultaneously, especially if it is a spiritual substance. For the teachers of theology do not admit that an angel exists in different places simultaneously. (Cf. John Damascene, On the Orthodox Faith, bk. 1, ch. 13 (PG 94:851–54); Bonaventure, In II Sent., d. 2, P. 2, a. 2, q. 2, resp.; Aquinas, In I Sent., d. 37, q. 3, a. 2; ST I.54.2.) Therefore, the soul cannot exist in different parts of the body.

On the contrary (1), Augustine says in On the Trinity 6 that the whole soul exists in the whole body and in each of its parts. (Augustine, On the Trinity, bk. 6, ch. 6, para. 8 (CCSL 50:235–37; PL 42:928–29).)

Furthermore (2), the soul gives to the body its act of existing only by being united to the body. But the soul confers the act of existing on the whole body and on each of its parts. Therefore, the whole soul exists in the whole body and in each of its parts.

Furthermore (3), the soul operates only where it exists. But the operations of the soul are seen to exist in each part of the body. Therefore, the soul exists in each part of the body.

I answer that the true solution to this question depends on the preceding one. (There is a remarkable correspondence between this response and that found in Aquinas’s On Spiritual Creatures, a. 4, resp.) For it was shown (Above: q. 9, resp., ad 13.) that the soul as the form of the body is not united to the whole body through the medium of any of its parts, but is united directly to the whole body because it is the form of the body as a whole and of each of its parts. And this must be maintained, for, since the body of a man or that of any other animal is a certain natural whole, it will be said to be one because it has one form whereby it is perfected, (Cf. Aristotle, Metaphysics 5.6, 1016b12–14; 7.17, 1041b5–28.) and not simply because it is an aggregate or a composition, as occurs in the case of a house and other things of this kind. Hence, each part of a man and that of an animal must receive its act of existing and species from the soul as its proper form. Therefore, the Philosopher says that when the soul leaves the body, neither the eye nor the flesh nor any part remains except in an equivocal sense. (Aristotle, On the Soul 2.1, 412b19–22; Metaphysics 7.10 1035b24–25; On the Parts of Animals 1.1, 640b34–35; Meteorology 4.12, 390a7–15.)

Moreover, it is impossible for a thing to receive its act of existing and species (as it does from a form) from a principle existing in separation from it, because this would be similar to the position of the Platonists, who maintained that such sensible things receive their act of existing and species by participating in forms which exist apart from things themselves. (Aristotle, Metaphysics 1.6, 987b1–8; 1.9, 991a20–b3; 7.8, 1033b19–1034a8; 12.6, 1071a17–30.) But a form must be an intrinsic principle of the thing whose act of existing it is responsible for, because form and matter are the intrinsic principles constituting the essence of a corporeal thing. (Cf. Aquinas, On Being and Essence, ch. 2; Commentary on the Book of Causes, proposition 5, n. 136.)

Hence, according to the teaching of Aristotle, if the soul as a form gives to each part of the body its act of existing and species, it must be present as a form in each part of the body. (Aristotle, On the Soul 2.1, 412b17–25; 412b4–9.) And for this reason, the soul is said to exist in the whole body because it is the form of the whole.

Therefore, if it is the form of each part of the body, it must exist in each part and not in the whole alone, nor in one part alone. Moreover, this definition of the soul is an appropriate one, (Aristotle, On the Soul 2.1, 412b4–6.) for the soul is the act of an organic body. However, an organic body is composed of different organs. Hence, if the soul as a form existed in one part of the body only, it would not be the act of an organic body, but that of one organ alone, for instance, the heart or some other part, and the remaining parts would be perfected by different forms. And thus, the whole would not be one thing by nature but merely by composition. Hence, it follows that the soul exists in the whole body and in each of its parts.

But since it is also asked whether the whole soul exists in the whole body and in each of its parts, we must consider how this is to be explained. For totality can be attributed to a form in a threefold manner, according to the three ways in which it is proper for a thing to have parts. (Cf. ST I.8.2, ad 3; I.76.8; On Spiritual Creatures, a. 4; SCG II.72.) For a thing has parts, in one way, resulting from quantitative division, that is, according as a number or a magnitude is divided. However, totality of number or that of magnitude does not apply to a form, except perhaps in an accidental way, for instance, in the case of forms which are divided accidentally by the division of a continuum, as whiteness is divided as a result of dividing a surface. A thing is said to be a totality in another way in relation to the essential parts of its species, as matter and form are said to be parts of a composite, and genus and difference, in a certain respect, parts of a species. This kind of totality is also attributed to simple essences by reason of their perfection, in this way, that as composites have a perfect species from the union of their essential principles, so also do substances and simple forms which have a perfect species in virtue of themselves. A thing is said to be a totality in a third way in relation to its active and passive powers, inasmuch as these are considered to be parts of it which are distinguished from one another because their operations differ.

Therefore, if we take a form which is divided as a result of dividing a continuum, and inquire whether the whole form is in each part of the body, for example, whether whiteness exists in its entirety in a part of the surface, and if the form is considered in relation to quantitative parts—which totality, indeed, pertains to whiteness accidentally—then the whole form does not exist in each part of the body, but the whole form exists in the whole body, and a part of the form in a part of the whole. However, if it is a question of totality so far as the species is concerned, then the whole form exists in each part of the body, for whiteness is as equally intense in any part as it is in the whole. But so far as its power is concerned, it is true that the whole form does not exist in each part, for the whiteness existing in a part of the surface cannot disperse as much light as the whiteness existing in the whole surface, just as the heat in a small fire alone cannot cause warmth like the heat in a large fire.

Now if we suppose, for the present, that there is only one soul in the human body—we will explain this later (Below: q. 11.)—we must maintain that it is not divided by dividing that species of quantity which is numerical in nature. It is also obvious that the soul is not divided by dividing a continuum. This is particularly true of the souls of perfect animals which do not live when dissected. However, it would perhaps be different in the case of the souls of ring-worms, in which there is one soul actually and many potentially, as the Philosopher teaches. (Aristotle, On the Soul 2.2, 413b13–22; cf. Aquinas, In I Sent., d. 8, q. 5, a. 3, ad 2; SCG II.86; On the Power of God, q. 3, a. 12, ad 5; Commentary on Aristotle’s On the Soul, bk. 2, lect. 14.) Therefore, in the case of the soul of man and that of any perfect animal, it follows that totality can be considered only so far as the soul’s species and its passive or active power are concerned.

Hence, we say that the soul by its very essence is the form of the body, and that it exists as such in each part of the body, as has been shown, (Above in this same response.) because the perfection of the species comes from the soul in virtue of its very essence. Consequently, the whole soul exists in each part of the body according to the whole of its specific perfection.

However, if totality is taken so far as the soul’s active and passive powers are concerned, then the whole soul does not exist in each part of the body. Nor, if we speak of the soul of man, does the whole soul, according to the totality of its powers, exist in the whole body. For it was shown in the preceding articles (Above, the responses in qq. 1–2, 5.) that the human soul possesses the power of performing certain operations without communicating in any way with the body, that is, the acts of understanding and willing, as it exceeds the capacity of the body. Hence, the intellect and the will are not the acts of any bodily organ.

However, with respect to those operations which the soul exercises through bodily organs, the soul’s active and passive powers as a whole exist in the whole body, although not in each part of the body, because different parts of the body are proportioned to different operations of the soul. (Cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 1, comm. 93; Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 14.) Consequently, with respect to any one power, the soul exists only in that part of the body which takes care of the operations exercised by that particular part.

Reply Obj. 1: Since matter exists for the sake of form, (Above: q. 8, resp.) and since a form is directed to a proper operation, the matter to which a form is united must be one that is suitable for the proper operations of that form, just as the matter of a saw must be iron, which is suitable for sawing due to its hardness. Hence, since the soul can exercise different operations because of the perfect power which it has, its matter must be a body composed of different parts suitable for the different operations of the soul, which parts are called organs. (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 14; SCG II.72.) And for this reason, the whole body, to which the soul is related principally as a form, is the organ of the soul. (Cf. Aristotle, On the Soul 2.1, 412a28; Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 1.) However, parts exist for the sake of the whole. Hence, it is only by being intrinsically related to the body as a whole that a part of the body is related to the soul as that which is properly and principally capable of being perfected by the soul. Consequently, it is not necessary for each part of an animal to be an organic body, even though the soul is the form of each of the animal’s parts.

Reply Obj. 2: Since matter exists for the sake of form, form gives an act of existing and species to matter inasmuch as matter is disposed for the operations of the form. And, therefore, the soul, even though it is one and simple in its essence, perfects the parts of the body in different ways, because the body, which is capable of being perfected by the soul, requires diversity in its parts in order that it may be disposed for the different operations of the soul.

Reply Obj. 3: Since the soul exists in a part of the body in the manner just described, (Above: resp.) no part of the soul is found outside the soul which is in this part of the body. However, it does not follow that no part of the soul exists outside this part of the body, but rather that no part of the soul exists outside the whole body which the soul perfects as a principle.

Reply Obj. 4: In this passage the Philosopher is speaking about the motive power of the soul. (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 18; ST I.76.8, ad 1.) For the body’s principle of motion exists in one part, namely, in the heart, and moves the whole body through this part. This is clear from the example which he gives of the ruler.

Reply Obj. 5: The mover of the heavens, so far as its substance is concerned, is not confined to some particular place. (Aristotle, Physics 8.10, 266a10–12; 267b17–18; On the Heavens 2.6, 288b1–6; Aquinas, Commentary on Aristotle’s Physics, bk. 8, lect. 23, n. 1169.) But the Philosopher intends to show where it is inasmuch as it is a principle of moving. And in this way, inasmuch as it is a principle of motion, (Pseudo-Augustine (Alcher of Clairvaux), The Spirit and the Soul, ch. 18 (PL 40:794); John of Rupella, Summa de anima, bk. 1, ch. 42 [XL].) the soul is in the heart. (Cf. Aquinas, On the Power of God, q. 3, a. 18, ad 10.)

Reply Obj. 6: The soul in plants, inasmuch as it is the principle of certain operations, is also said to exist in the midst of their upper and lower parts. The soul exists in animals in the same way.

Reply Obj. 7: Therefore, each part of an animal is not an animal as each part of fire is fire, because every operation of fire is found in each part of fire. However, all the operations of an animal are not found in each of its parts. This is particularly true of perfect animals.

Reply Obj. 8: The conclusion of this argument is that the whole soul, so far as its power is concerned, does not exist in each part of the body. This was shown to be true. (Above: resp.)

Reply Obj. 9: The Philosopher does not distinguish parts in the soul with respect to its essence, but with respect to its powers. Hence, he says that, as the soul exists in the whole body, so also does a part of the soul exist in a part of the body. For as the whole organic body is so constituted that it may serve the operations of the soul which are exercised through it, so also is one organ disposed to one particular operation.

Reply Obj. 10: A power of the soul is rooted in its essence. Therefore, wherever a power of the soul exists, there also does the essence of the soul exist. Hence, the Philosopher’s statement that, if the eye of an animal were itself an animal, sight would be its soul, is not to be understood of a power of the soul without its essence, just as the sensitive soul is said to be the form of the whole body through its essence, not through its sensory power. (Aristotle, On the Soul 2.1, 412b18–22; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 2.)

Reply Obj. 11: Since the soul operates in different parts of the body through one particular power—moreover the body is disposed in this way that it is proportioned to the soul’s act of existing through the action of the soul itself which is the efficient cause of the body, as Aristotle says in On the Soul 2—it is necessary that the disposition of the different parts of the body, inasmuch as they are capable of being perfected by the soul, depend on one first part of the body, namely, on the heart. (Aristotle, On the Soul 2.4, 415b8–12.) For this reason, the life of the other parts depends upon the heart because, after the necessary dispositions cease to exist, the soul is not united as a form to the body. However, this does not prevent the soul from being the form of each part of the body directly.

Reply Obj. 12: The soul is moved or at rest only in an accidental way when the body is moved or at rest. (Cf. Aristotle, On the Soul 1.3, 406a12–b15.) Moreover, it is not incongruous for a thing to be moved and at rest accidentally at one and the same time, just as it is not implausible for a thing to be moved accidentally by contrary movements, as for instance, when someone on a ship walks in the direction opposite to that of the course of the ship.

Reply Obj. 13: Although all powers of the soul are rooted in its essence, yet each part of the body is informed by the soul in the manner befitting each. Therefore, different powers of the soul exist in different parts of the body. But it is not necessary that all of the soul’s powers exist in each part of the body.

Reply Obj. 14: When it is said that one thing exists in another in accordance with the mode of the thing in which it exists, (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 12.) this is understood of the mode of its capacity, not of its nature. For it is not necessary that whatever exists in something else have the nature and properties of that thing in which it exists, but that it be received in that thing according to the thing’s capacity, because it is obvious that water does not have the nature of the vessel in which it exists. Hence, it is not necessary for the soul to possess this characteristic of a body, namely, that wherever one part exists, another may not exist.

Reply Obj. 15: Ringworms continue to live after they have been dissected, not only because their soul exists in each part of the body, but because their soul, being imperfect and performing a minimum of operations, requires the least diversity of parts. This is also found in any part segregated from a living thing of this sort. (Cf. Aristotle, On the Soul 1.5, 411b19; The History of Animals 1.1, 487a32; On Youth and Old Age 1.2, 468b9–12; Aquinas, On the Power of God, q. 3, a. 12, ad 5; In I Sent., d. 8, q. 5, a. 3, ad 2; In II Sent., d. 18, q. 2, a. 3; Commentary on Aristotle’s On the Soul, bk. 1, lect. 14.) Hence, a soul remains in each part because each part retains that disposition whereby the whole body is made capable of being perfected by a soul. However, the soul exists differently in perfect animals.

Reply Obj. 16: The form of a house, like other artificial forms, is an accidental one. Hence, it does not give to the whole house and to each of its parts their act of existing and species. Indeed, a whole of this sort is not a substantial unity but is one by aggregation. However, the soul is the substantial form of the body, giving to the whole body and to each of its parts their act of existing and species. Furthermore, the whole constituted of these parts is a substantial unity. Hence, there is no similarity.

Reply Obj. 17: Although the soul is one and simple in essence, yet it is capable of performing different operations. And because the soul by nature gives its act of existing and species to what it is able to perfect, inasmuch as it is the form of the body by its very essence—moreover, those things existing naturally, exist for an end—the soul must establish a diversity of parts in the body inasmuch as this is required for its different operations. It is also true in the light of such diversity, which is to be attributed to the end, and not to the form alone, that it is more apparent that nature acts for an end in the constitution of living things than it is in the case of other natural things in which one form perfects, (Cf. Aristotle, Physics 2.8, 198b34–199b33.) in a uniform way, what it is able to perfect.

Reply Obj. 18: The simplicity of the soul and that of an angel must not be thought of in terms of the simplicity of the point, which has a definite position in a continuum, and, therefore, because it is simple cannot exist in different parts of the continuum at one and the same time. But the angel and the soul are said to be simple because they lack quantity altogether, and thus are related to a continuum only by contact of power. (Cf. Nemesius, On the Nature of Man, ch. 3.) Hence, that whole, which is contacted by an angel’s power, is present to the angel—which is not united to it as a form—as a single place; and it is present to the soul—which is united to it as a form—as a single thing able to be perfected. And just as the whole angel exists in each part of the place it is present in by contact of power, so also does the whole soul exist in each part of what it is able to perfect.