Article 14 — The incorruptibility of the human soul

Fourteenth, it is asked about the incorruptibility of the human soul. (Parallel texts: ST I.75.6; SCG II.79–81; Quodlibet X, q. 3, a. 2; In II Sent., d. 19, q. 1, a. 1; In IV Sent., d. 50, q. 1, a. 1; Compendium theologiae, bk. 1, ch. 84.)

Obj. 1: It seems that the soul is corruptible, for we read, the fate of the sons of man and the fate of beasts is the same; as one dies, so dies the other (Eccl 3:19). (Cf. ST I.75.6, obj. 1; SCG II.79; In II Sent., d. 19, q. 1, a. 1, obj. 1.) Now when beasts die, their soul perishes with them. Consequently, when a man dies, his soul perishes along with his body.

Obj. 2: Further, it is said that the corruptible and the incorruptible are diverse in genus, as is said in Metaphysics 10. (Aristotle, Metaphysics 10.10, 1058b26–29.) But the human soul and the soul of beasts are not diverse in genus, because man belongs to the same genus as the beast. With respect to corruptibility and incorruptibility, therefore, the soul of man and that of the beasts do not differ. But the soul of the beast is corruptible. Therefore, the human soul is not incorruptible.

Obj. 3: Further, Damascene says that an angel is endowed with incorruptibility, not by virtue of its own nature, but by the gift of grace. (John Damascene, On the Orthodox Faith, bk. 2, ch. 3 [ch. 17] (PG 94:867); John of Rupella, Summa de anima, bk. 1, ch. 45 [XLIII].) The angel, however, is not a soul inferior to the human. Consequently, the soul is not incorruptible by its very nature.

Obj. 4: Further, the Philosopher proves in Physics 8 that the prime mover has infinite power because he moves in infinite time. (Aristotle, Physics 8.10, 267b19–26.) Hence, if the soul has the power of remaining in existence for an infinite length of time, it follows that this power is itself infinite. But the essence of an infinite power is not finite. Therefore, if the soul is incorruptible, its essence is infinite. But this is impossible, for the divine essence alone is infinite. Consequently, the human soul is not incorruptible.

Obj. 5: It may be objected that the soul is incorruptible, not by virtue of its own essence, but by virtue of the power of God.

On the contrary, whatever does not belong to a thing by virtue of its own essence is not essential to it; and, as the Philosopher points out in Metaphysics 10, corruptible and incorruptible are predicated essentially of everything whatever. (Aristotle, Metaphysics 10.10, 1058b26–1059a10.) Hence, if the soul is incorruptible, it must necessarily be incorruptible in virtue of its own essence.

Obj. 6: Further, everything that exists is either corruptible or incorruptible. Hence, if the human soul is not incorruptible by virtue of its very nature, it follows that it is corruptible by virtue of its very nature.

Obj. 7: Further, every incorruptible thing has the power of existing forever. Thus, if the human soul is incorruptible, it has the power of existing forever. In that case, the human soul did not come into existence but always existed. This is contrary to faith. (Cf. Aristotle, On the Heavens 1.11, 281a28–282a4; Aquinas, Commentary on Aristotle’s On the Heavens, bk. 1, lect. 26, n. 258; SCG II.83.)

Obj. 8: Further, Augustine says that as God is the life of the soul, so the soul is the life of the body. (Augustine, City of God, bk. 19, ch. 26 (CCSL 48:696–97; PL 41:656–57).) But death is the privation of life. Therefore, by death the soul is deprived of life and is destroyed.

Obj. 9: Further, a form has actual existence only in the thing in which it exists. Thus, if the soul is the form of the body, it can exist only in a body. Hence, it ceases to exist when the body corrupts. (Cf. Aquinas, In II Sent., d. 19, q. 1, a. 1, obj. 3.)

Obj. 10: The objection may be raised that, although this argument truly applies to the soul as a form, it does not hold so far as the essence of the soul is concerned.

On the contrary, the soul is not the form of the body in an accidental way; otherwise, since the soul is constitutive of man inasmuch as it is the form of the body, it would follow that man would be a being accidentally. But whatever does not belong to a thing accidentally belongs to it by its very essence. Consequently, the soul is a form according to its very essence. Hence, if the soul is corruptible inasmuch as it is a form, it will likewise be corruptible according to its very essence.

Obj. 11: Further, things having one and the same act of existing in common are so intimately related to each other that, if one of them is corrupted, the other or others are thereby corrupted also. But the soul and the body have one and the same act of existing in common, namely, the act of existing of a man. Therefore, when the body is corrupted, the soul is also corrupted.

Obj. 12: Further, in man the sensitive soul and the rational soul are substantially one and the same. But the sensitive soul is corruptible. Therefore, the rational soul is also corruptible.

Obj. 13: Further, a form ought to be proportioned to a matter. But the human soul exists in the body as a form in matter. Therefore, since the body is corruptible, so too is the soul.

Obj. 14: Further, if the soul can exist in separation from the body, then the soul must be able to perform some operation without the body, for no substance is functionless. (Cf. Averroes, Commentary on Aristotle’s Metaphysics, bk. 2, comm. 1.) Now without the body the soul can do nothing; it cannot even perform an act of knowledge. This is evident from the fact that understanding is impossible without a phantasm, as the Philosopher says, and there are no phantasms without the body. (Aristotle, On the Soul 3.7, 431a14–17.) Consequently, the soul cannot exist in separation from the body but ceases to exist when the body corrupts.

Obj. 15: Further, the argument that the human soul is incorruptible could be based only on the assumption that it is intellective. But it seems that the soul is not intellective. For the highest part of a being of an inferior nature in some way strives to imitate the action of the being superior to it. Thus, the ape in some way imitates the action of a man, and yet it does not attain to the human level. Similarly, in view of the fact that man occupies the highest rank in the order of material things, it seems that he in some fashion imitates the action of the separate intellectual substances, namely, the act of understanding, and yet does not really attain to it. Hence, there does not seem to be any necessary reason for holding that the human soul is immortal.

Obj. 16: Further, either all or at least most of the members of any given species participate in the type of activity proper to that species. (Cf. Aristotle, On the Soul 3.9, 432b21–22; Aquinas, Commentary on the Nicomachean Ethics, bk. 1, lect. 10 and 14.) But actually very few men succeed in being intelligent. Intellectual operation, therefore, is not the type of operation proper to the human soul. Consequently, the human soul need not be incorruptible simply because it is intellectual.

Obj. 17: Further, the Philosopher points out in Physics 1 that every finite thing comes to an end, since something is always being taken away from it. (Aristotle, Physics 1.4, 187b25.) But the natural good of the soul is a finite good. (Cf. Aristotle, Nicomachean Ethics 1.8, 1098b12–20; Aquinas, Commentary on the Nicomachean Ethics, bk. 1, lect. 12.) Therefore, since the natural good of the soul is diminished through sin, it seems that in the end this good will be totally removed, and, hence, that the human soul will at some time cease to exist.

Obj. 18: Further, it is evident from our observation of the soul’s operations that when the body grows weak, the soul grows weak also. Therefore, when the body corrupts, the soul also corrupts.

Obj. 19: Further, everything that is created can also be annihilated. Now the human soul has been created; therefore, it can be annihilated. (Cf. Aquinas, In II Sent., d. 19, q. 1, a. 1, obj. 7.) And thus, it follows that the soul is corruptible.

Obj. 20: Further, so long as a cause continues to operate, its effect continues to exist. Now the soul is the cause of life in the body. Therefore, if the soul always continues to exist, it seems that the body should go on living forever. This is clearly false.

Obj. 21: Further, everything that subsists of itself is a particular thing belonging to some species or genus. Now since the human soul is a form, it appears that it is not a particular thing, and that it does not belong to a species or to a genus as an individual member of the former or as a species of the latter. For to exist in a genus or in a species belongs to a composite of matter and form, and not to matter or to form taken separately, except by reduction. Therefore, the human soul is not a self-subsisting entity, and thus cannot continue to exist once the body has corrupted.

On the contrary (1), it is written, God created man for incorruption and made him in the image of his own likeness (Wis 2:23), from which it may be inferred that man is inexterminable, that is, incorruptible, inasmuch as he is made in the image of God. But as Augustine says in the book On the Trinity, it is with respect to man’s soul that he is made in the image of God. (Augustine, On the Trinity, bk. 10, ch. 12 (CCSL 50:332; PL 42:984).) Therefore, the human soul is incorruptible.

Furthermore (2), everything that is corrupted has contraries, or is made up of contraries. But the human soul is completely devoid of contrariety, for even those things which are themselves contraries are not contraries in the soul, because the concepts of contraries existing in the soul are not themselves actual contraries. (Cf. Aristotle, Metaphysics 7.7, 1032b1–5; SCG II.76.) Hence, the human soul is incorruptible.

Furthermore (3), the heavenly bodies are said to be incorruptible because they do not have matter of the sort found in generable and corruptible things. But the human soul is absolutely immaterial. This is evident from the fact that it receives the species of things immaterially. Hence, the soul is incorruptible.

Furthermore (4), the Philosopher says that the intellect differs from other powers as the eternal differs from the perishable. (Aristotle, On the Soul 2.2, 413b24–29; Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 4; In II Sent., d. 19, q. 1, a. 1, s.c. 1.) But the intellect is a part of the soul, as he himself points out. (Cf. Aristotle, On the Soul 3.4, 429a10; Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 1.) Therefore, the human soul is incorruptible.

I answer that it must necessarily be granted that the human soul is incorruptible. For proof of this, we must take into consideration the fact that whatever belongs to a thing in virtue of its very nature cannot be taken away from it; for example, animality cannot be taken away from man, nor can the even and odd be taken away from number. Moreover, it is evident that the act of existing in itself is a result of a form, for everything has its act of existing from its proper form. (Cf. Aristotle, On the Soul 2.4, 415b12–14.) Wherefore, its act of existing can in no way be separated from its form. Therefore, things composed of matter and form are corrupted by losing the form that gives them their act of existing. Moreover, a form itself cannot be corrupted in itself, but is corrupted accidentally as a result of the disintegration of the composite, inasmuch as the composite, which exists in virtue of its form, ceases to exist as a composite. (Cf. Aristotle, Metaphysics 7.8, 1033b4–8; Aquinas, Commentary on Aristotle’s Metaphysics, bk. 7, lect. 9, nn. 1480–81; Quodlibet X, q. 3, a. 2, resp.) This, indeed, is the case if the form is one that does not have an act of existing in itself, but is merely that by which a composite exists. Now if there is a form having an act of existing in itself, then that form must be incorruptible. For a thing having an act of existing does not cease to exist unless its form is separated from it. (Cf. Aquinas, In II Sent., d. 19, q. 1, a. 1, ad 2 and 3; SCG II.79; ST I.75.6, resp.) Hence, if the thing having an act of existing is itself a form, it is impossible for its act of existing to be separated from it.

Now it is evident that the principle by which a man understands is a form having its act of existing in itself and is not merely that by which something exists. (Cf. Aquinas, In II Sent., d. 19, q. 1, a. 1, ad 2; SCG II.79; On the Power of God, q. 3, a. 10, ad 16; ST I.75.6, resp.) For, as the Philosopher proves in On the Soul 3, understanding is not an act executed by any bodily organ. (Aristotle, On the Soul 3.4, 429b3.) The main reason why there is no bodily organ capable of receiving the sensible forms of all natural things is that the recipient must itself be deprived of the nature of the thing received, just as the pupil of the eye does not possess the color that it sees. (Cf. Aristotle, On the Soul 2.7, 418b26–28; Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 15; bk. 3, lect. 1, n. 680.) Now every bodily organ possesses a sensible nature. But the intellect, by which we understand, is capable of apprehending all sensible natures. (Cf. Aristotle, On the Soul 3.4, 429a21–22; 3.5, 430a14–15; Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 1 and 4.) Therefore, its operation, namely, understanding, cannot be carried out by a bodily organ. Thus, it is clear that the intellect has an operation of its own in which the body does not share. Now a thing operates in accordance with its nature, for things that exist of themselves have an operation of their own, whereas things that do not exist of themselves have no operation of their own. (Cf. Aristotle, On the Soul 1.1, 403a10–12; Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 2.) For example, heat in itself does not produce warmth, but something hot. Consequently, it is evident that the intellective principle, by which man understands, has its own mode of existing superior to that of the body and not dependent upon it. (Cf. Aristotle, On the Soul 3.4, 429b5; Avicenna, De anima, part 5, ch. 2; Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 6; Aquinas, In II Sent., d. 19, q. 1, a. 1, resp.)

It is also evident that an intellective principle of this sort is not a thing composed of matter and form, because the species of things are received in it in an absolutely immaterial way, as is shown by the fact that the intellect knows universals, which are considered in abstraction from matter and from material conditions. (Cf. SCG II.79.) The sole conclusion to be drawn from all this, then, is that the intellective principle, by which man understands, is a form having its act of existing in itself. Therefore, this principle must be incorruptible. This indeed agrees with the Philosopher’s dictum that the intellect is something divine and everlasting. (Aristotle, On the Generation of Animals 2.3, 736b27–28; On the Soul 1.4, 408b29; 3.5, 430a22.) Now it was shown in preceding articles (Above: qq. 2–3, 5.) that the intellective principle, by which man understands, is not a substance existing apart from man but is something formally inhering in him which is either the soul or a part of the soul. Thus, from the foregoing considerations, we conclude that the human soul is incorruptible.

Now all those who held that the human soul is corruptible missed some of the points we have already made. Some of these people, holding that the soul is a body, declared that it is not a form in its entirety, but a thing composed of matter and form. (Cf. Aristotle, On the Soul 1.2, 404a1–405b2.) Others held that the intellect does not differ from the senses, and so they declared that the intellect does not operate except through a bodily organ—that it does not have a higher mode of existence than that of the body, and, therefore, that it is not a form having an act of existing in its own right. (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 2; bk. 2, lect. 28; SCG III.84.) Still others held that the intellect, by which man understands, is a separate substance. (Cf. Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 1 and 5.) But the falsity of all these opinions has been demonstrated in preceding articles. (See above: qq. 1–3.) Therefore, it remains that the human soul is incorruptible.

Two additional arguments can be considered as an indication of this.

First, respecting the intellect itself, because we see that even those things which are corruptible in themselves are incorruptible so far as they are perceived by the intellect. For the intellect apprehends things in and through universal concepts, and things existing in this mode are not subject to corruption. (Cf. Aristotle, On the Soul 2.5, 417b23; Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 12.)

Second, the natural appetite also provides an argument for the incorruptibility of the soul. Natural appetite cannot be frustrated. Now we observe in men the desire for perpetual existence. (Cf. SCG II.79; ST I.75.6, resp.; Augustine, On the Trinity, bk. 13, ch. 8 (CCSL 50:396–97; PL 42:1022–23); Aristotle, Nicomachean Ethics 10.7, 1177b26–27.) This desire is grounded in reason. For since existing is desirable in itself, an intelligent being who apprehends existence in the absolute sense, and not merely the here and now, must desire existence in the absolute sense and for all time. Hence, it is clear that this desire is not vain, but that man, in virtue of his intellective soul, is incorruptible.

Reply Obj. 1: In the book of Ecclesiastes, Solomon speaks as a popular orator, at one time representing the wisdom of the wise, at another the stupidity of fools. (Ecclesiastes 3:19; cf. Aquinas, In II Sent., d. 19, q. 1, a. 1, ad 1; SCG II.79; ST I.75.6, ad 1.) The text quoted is an example of the latter. Or it may be said that the death of man and that of the beast is one and the same so far as the dissolution of the composite is concerned, since, for the one as for the other, this dissolution is brought about by the separation of the soul from the body. But there is this difference: after that separation occurs, the human soul remains in existence, whereas the soul of the brute does not.

Reply Obj. 2: Even if the human soul and the soul of brutes were brought under the same genus, nevertheless they would still exist in different natural genera; for the corruptible and the incorruptible are, of necessity, different in genus in reality, although they can be arranged under one common concept—that is, from the standpoint of logic, they can be considered under the same generic account. Moreover, the soul does not exist in a genus as a species thereof, but as a part of a species. Yet both the composites in question are corruptible: the composite of which the human soul is a part, as well as the composite of which the soul of brutes is a part. Hence, there is no reason why both types of soul may not belong to one and the same genus.

Reply Obj. 3: As Augustine says, true immortality and true immutability are the same. (Augustine, On the Immortality of the Soul, cc. 1–5 (CSEL 89:101–7; PL 32:1021–25).) Moreover, it is through grace that both the soul and the angel possess that immutability which results from free choice and which prevents them from changing from good to evil.

Reply Obj. 4: The act of existing is related to a form as something consequent upon the form in virtue of its very nature, and not as an effect to its efficient cause, in the manner in which motion, for example, is related to the power of the thing that produces it. Consequently, although the fact that a thing can move in infinite time may prove that its movement is infinite, nevertheless the fact that a thing can exist in infinite time does not prove that the form whereby it exists is infinite any more than the fact that a given quantity is always equal proves that it is infinite. On the contrary, the fact that a thing exists in infinite time proves the infinite power of that which is the cause of its being.

Reply Obj. 5: Corruptible and incorruptible are essential predicates because they belong to the essence of a thing as a formal or material principle and not as an active principle. However, the active principle of the perpetual act of existing enjoyed by some things is external to them.

Reply Obj. 6: The answer to the sixth objection is clear from what was said above.

Reply Obj. 7: The soul has the power of existing forever but it did not always have that power. (The soul did not have that power before it existed.) Hence, the soul need not always have existed, but it must never cease to exist in the future. (Cf. Aquinas, Quodlibet X, q. 3, a. 2, ad 2; SCG II.84; ST I.46.1, ad 2.)

Reply Obj. 8: The soul is called the form of the body inasmuch as it is the cause of life, just as the form is the principle of a thing’s act of existing; because, for living things, to live is to exist, as the Philosopher says in On the Soul 2. (Aristotle, On the Soul 2.4, 415b8–13.)

Reply Obj. 9: The soul is a form of such a kind that its act of existing does not depend on the subject of which it is the form. Its proper operation proves this, as was shown above. (Above: qq. 8–9.)

Reply Obj. 10: Although the soul is a form by its very essence, nevertheless inasmuch as it is a form of a particular kind, that is, a subsisting form, it can have a certain character which does not belong to it simply as a form—just as the act of understanding does not belong to man inasmuch as he is an animal, although he is an animal by his very essence.

Reply Obj. 11: Although the soul and the body of man have one and the same act of existing in common, nevertheless that act of existing is communicated to the body by the soul. (Cf. Aquinas, In II Sent., d. 19, q. 1, a. 1, ad 2; Quodlibet X, q. 3, a. 2, ad 3; SCG II.68; ST I.76.1, ad 5.) Thus, the human soul communicates to the body that very act of existing by which the soul itself subsists. This has been shown in preceding articles. (See above: q. 1, ad 1.) Hence, the soul continues to exist when the body has corrupted.

Reply Obj. 12: The sensitive soul in brute animals is corruptible, but since in man the sensitive soul is identical in substance with the rational soul, it is incorruptible. (Cf. SCG II.82; ST I.75.3.)

Reply Obj. 13: The human body is the matter belonging to the human soul and proportioned to the soul’s operations. But, as was shown above, (Above: q. 8.) bodily disintegration and other defects occur by reason of the very nature of matter. Or we may reply that the death of the body is the result of sin, (Specifically, original sin.) and not an original determination of nature.

Reply Obj. 14: The Philosopher’s statement that understanding cannot take place without a phantasm applies to the state of the present life in which man understands by his soul. (Aristotle, On the Soul 3.7, 431a16–17.) However, the separated soul will understand in a different way. (See below: qq. 17–21.)

Reply Obj. 15: Although the human soul does not attain to that mode of understanding which superior substances possess, nevertheless it does attain to understanding in a certain way, and this suffices to show its incorruptibility.

Reply Obj. 16: Although few people arrive at perfect understanding, yet all people achieve some kind or degree of understanding. The first principles of demonstration are obviously common conceptions of the soul which are perceived by the intellect. (Cf. Aquinas, Commentary on Aristotle’s Posterior Analytics, bk. 1, lect. 18.)

Reply Obj. 17: Sin takes away grace totally, but it does not take anything away from the essence of a thing. (Cf. Aquinas, On Evil, q. 2, aa. 11–12.) However, sin does take away something of the inclination toward or aptitude for grace, and inasmuch as every sin stems from a contrary disposition, sin is said to take away some part of that good of nature which is aptitude for grace. But sin never destroys completely the good of nature because, under contrary dispositions, the potentiality for good always remains, though by sin that potentiality is further and further removed from actualization.

Reply Obj. 18: The soul does not grow feeble when the body grows feeble, not even the sensitive soul. For, as the Philosopher observes in On the Soul 1, if an old man acquired the eye of a youth, he would see as well as the youth does. (Aristotle, On the Soul 1.4, 408b20–22; Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 10; SCG II.79.) From this it is clear that functional debility does not result from a debility of the soul but from that of a bodily organ.

Reply Obj. 19: Whatever receives existence “from nothing” can be reduced to nothing unless it is conserved in being by a guiding hand. (Cf. ST I.75.6, ad 2.) Yet it is not for this reason that a thing is said to be corruptible, but because some principle of corruption exists in the thing itself. So it is clear that corruptible and incorruptible are essential predicates. (Cf. Aristotle, Metaphysics 10.10, 1058b26–28.)

Reply Obj. 20: Although the soul, which is the cause of life, is incorruptible, nevertheless the body, which receives life from the soul, is subject to change; and because of this, the body loses that disposition by which it prepared to receive life, and in this way the corruption of man is brought about.

Reply Obj. 21: Although the soul can exist of itself, yet it does not itself possess a species, for it is part of a species.