Article 3 — Whether the spiritual substance, which is the human soul, is united to the body through a medium

Third, it is asked whether the spiritual substance, which is the human soul, is united to the body through a medium. (Parallel texts: In II Sent., d. 1, q. 2, a. 4; SCG II.71; Disputed Questions on the Soul, q. 9; Commentary on Aristotle’s On the Soul, bk. 2, lect. 1; ST I.76.3–4, 6–7.)

Obj. 1: And it would seem that it is. For Dionysius says in the thirteenth chapter of Celestial Hierarchy (Pseudo-Dionysius, The Celestial Hierarchy, ch. 13, para. 3 (PG 3:302).) that the highest things are joined to the lowest through intermediates. But between a spiritual substance and a body there are intermediates, the vegetative soul and the sensitive soul. Therefore, the spiritual substance which is the rational soul is united to the body through the medium of the vegetative and the sensitive souls.

Obj. 2: Furthermore, the Philosopher says in On the Soul 2 that it is the act of an organic body having life potentially. (Aristotle, On the Soul 2.1, 412a27–28; 412b4–5.) The physical organic body, therefore, having life potentially, is related to the soul as matter is to form. But this latter, namely, the physical organic body, does not exist except through some substantial form. Therefore, that substantial form, whatever it may be, is present in matter before the spiritual substance which is the rational soul, and so for the same reason are the other subsequent forms, which are the sensitive and the vegetative souls. (Cf. Aquinas, Disputed Questions on the Soul, q. 9, obj. 7.)

Obj. 3: Furthermore, although matter is not a genus and form is not a difference, because neither of these is predicated of the composite, whereas genus and difference are predicated of the species, nevertheless, according to the Philosopher in Metaphysics 8, (Aristotle, Metaphysics 8.2, 1043a2–7, 1043a19–21; 8.3, 1043b30–32.) the genus is derived from the matter and the difference from the form. But the genus of man is “animal,” which is derived from a sensitive nature, whereas the difference is “rational,” which is derived from the rational soul. Therefore, the sensitive nature is related to the rational soul as matter is to form. But the sensitive nature is perfected by the sensitive soul. Therefore, the sensitive soul exists in nature before the rational soul, and for the same reason so do all the other previous forms.

Obj. 4: Furthermore, as is proven in Physics 8, (Aristotle, Physics 8.4, 254b22; 8.5, 257b12–13.) every self-moving thing is divided into two parts, of which one is the mover and the other the object moved. But man and any animal whatever is a self-moving thing. Now the motor part of it is the soul, and the moved part cannot be mere matter but must be a body, because everything that is moved is a body, as is proven in Physics 6. (Aristotle, Physics 6.4, 234b10–20; 6.10.) Now a body exists through some form. Therefore, some form exists in matter previous to the soul; and so we come to the same conclusion as before.

Obj. 5: Furthermore, Damascene says that so great is the simplicity of the divine essence, that it is not fitting for the Word to be united to the flesh except through the medium of a soul. (Peter Lombard (d. 1160 AD), Sentences, bk. 3, d. 2, ch. 2 (5), para. 1 (PL 192:760); see John Damascene, On the Orthodox Faith, bk. 3, ch. 6 (PG 94:1006).) Therefore, a difference based on “simple” and “composite” prevents some things from being able to be conjoined without a medium. But the rational soul and the body differ very widely on a basis of “simple” and “composite.” Therefore, it must be the case that they are united through a medium.

Obj. 6: Furthermore, Augustine says in his book The Spirit and the Soul that the soul which is truly a spirit and the flesh which is truly a body are easily and conveniently conjoined in their extremities, that is, in the soul’s imagination, which is not a body but is like a body, and in the body’s sense-appetite, which is almost a spirit, because it cannot come into being without the soul. (Alcher of Clairvaux, The Spirit and the Soul, ch. 14 (PL 40:789).) The soul, then, is conjoined to the body through two media, namely, the imagination and the sense-appetite.

Obj. 7: Furthermore, in the same book it is said, although the soul is incorporeal, it manages the body through the more subtle part of the nature of its body, that is, through fire and air. (Alcher of Clairvaux, The Spirit and the Soul, ch. 15 (PL 40:791).) Now the soul manages the body in the same way in which it is united to it; for when the elements through which the soul manages the body are lacking, the soul departs from the body, as Augustine says in On the Literal Interpretation of Genesis 7. (Augustine, On the Literal Interpretation of Genesis, bk. 7, ch. 19, para. 25 (CSEL 28.1:215–16; PL 34:364); bk. 3, ch. 5, para. 7 (CSEL 28.1:67; PL 34:282).) Therefore, the soul is united to the body through a medium. (Cf. ST I.76.7, obj. 1.)

Obj. 8: Furthermore, things which differ most widely are not conjoined unless through a medium. But the corruptible and the incorruptible differ most widely, as is said in Metaphysics 10. (Aristotle, Metaphysics 10.10, 1058b28–29; 1058b36–1059a1; Averroes, Commentary on Aristotle’s Metaphysics, bk. 10, comm. 26.) Therefore, the human soul, which is incorruptible, is not united to the corruptible body except through a medium. (A similar argument is provided in: Aquinas, Disputed Questions on the Soul, q. 9, obj. 18.)

Obj. 9: Furthermore, a certain philosopher says in the book De differentia spiritus et animae that the soul is united to the body through the medium of a spirit. (Constabulus (Qusta ibn Luqa, 820–912 AD), De differentia spiritus et animae, ch. 4.) Therefore, it is united to it through a medium.

Obj. 10: Furthermore, those things which are essentially different are not united without a medium. (Cf. ST I.3.7, resp.; I.12.3, resp.; I.65.1, resp.; II-II.171.4, resp.) For there must be something which makes these one, as is clear from Metaphysics 8. (Aristotle, Metaphysics 8.6, 1045a8–10.) But the soul and the body are essentially different. Therefore they cannot be united except through a medium.

Obj. 11: Furthermore, the soul is united to the body in order that it may be perfected by a union of this sort, because the form does not exist for matter, but matter for form. Now the soul is perfected in consequence of its union with the body, especially as regards understanding through phantasms, namely, insofar as it understands by abstracting from phantasms. Therefore, it is united to the body through phantasms, which are neither of the essence of the body nor of the essence of the soul. Therefore, the soul is united to the body through a medium.

Obj. 12: Furthermore, before the coming of the rational soul the body in the womb of the mother has some form. Now when the rational soul comes, it cannot be said that this form disappears, because it does not lapse into nothingness, nor would it be possible to specify anything into which it might return. Therefore, some form exists in the matter previous to the rational soul.

Obj. 13: Furthermore, in the embryo before the coming of the rational soul, vital functions are manifest, as is clear from On the Generation of Animals 16. (Aristotle, On the Generation of Animals 2.3, 736a32–b1, b12.) But vital functions come only from the soul. Therefore, another soul exists in the body before the coming of the rational soul, and thus it seems that the rational soul is united to the body through the medium of another soul.

Obj. 14: Furthermore, since abstraction is not falsification, as is said in Physics 2, (Aristotle, Physics 2.2, 193b35.) the body about which mathematicians speak must have some sort of actual being. Since, therefore, it is not separated from sensible things, it follows that it is in the sensible things. But for the very being of a body there is needed a form of corporeity. Therefore, the form of corporeity, at least, is presupposed in the human body, which is a sensible body, prior to the human soul.

Obj. 15: Furthermore, in Metaphysics 7 (Aristotle, Metaphysics 7.10, 1034b20–22; 7.11, 1036a26.) it is said that every definition has parts, and that the parts of a definition are forms. (Cf. Aristotle, Physics 2.3, 194b26.) In anything that is defined, therefore, there must be several forms. Since, therefore, man is a kind of defined thing, it is necessary to posit in him several forms, and so some form exists before the rational soul.

Obj. 16: Furthermore, nothing imparts what it does not possess. (Cf. Aristotle, On Sophistical Refutations 1.10, 171a9; 1.22 178a37; Augustine, On Free Will, bk. 2, ch. 17, para. 45 (PL 32:1265; CSEL 74:80; CCSL 29:267).) But the rational soul does not possess corporeity, since it is incorporeal; therefore, it does not impart corporeity to man, and so man must have this from another form.

Obj. 17: Furthermore, the Commentator says that prime matter receives universal forms before particular ones; (Averroes, Commentary on Aristotle’s Metaphysics, bk. 1, comm. 17.) thus, it receives the form “body” before the form “animate body,” and so forth. Since, therefore, the human soul is the ultimate form and the most specific one, it seems that it presupposes other universal forms in matter.

Obj. 18: Furthermore, the Commentator says in his book On the Substance of the Celestial Sphere (Averroes, On the Substance of the Celestial Sphere, ch. 1.) that dimensions exist in matter before the elementary forms. But dimensions are accidents, and presuppose some substantial form in matter; otherwise, accidental actual being would be prior to substantial actual being. Therefore, prior to the form of a simple element there exists beforehand in matter some other substantial form; hence, for all the greater reason, it is prior to the rational soul.

Obj. 19: Furthermore, according to the Philosopher in his book On Generation and Corruption, (Aristotle, On Generation and Corruption 2.4, 331a7–332a2.) air is more easily converted into fire than water because it agrees with fire in one quality, namely, heat. When, therefore, fire comes into being out of air, it is necessary that the heat remain the same in species. For if the heat of fire and the heat of air were different in species, there would be eight primary qualities and not four only, since the same reasoning would apply to the other qualities, every one of which is found in two elements. If, therefore, one were to say that it remains the same in species but different in number, the conversion of air into fire will not be easier than that of water into fire, because the form of fire will have to break up two qualities in the air just as it does in water. The only remaining alternative, therefore, is that the heat is the same in number. But this cannot be unless there is already in existence some substantial form, which remains one in both and preserves the subject of heat as one; for an accident cannot be one in number unless its subject is already one. (Cf. ST I.29.1, resp.; III.77.2, resp.) One must, therefore, say that prior to the form of a simple body, some substantial form is presupposed in matter; much more so, then, is it prior to the rational soul.

Obj. 20: Furthermore, prime matter considered simply in itself is quite indifferent to all forms. (Cf. SCG II.44.) If, then, certain forms and dispositions, through which prime matter is specialized to this or to that particular form, do not exist before others, this particular form will not be received in prime matter in preference to another particular form.

Obj. 21: Furthermore, matter is united to form through the potency whereby it is able to underlie form. But that potency is not the same as the essence of matter; (ST I.77.1, resp.; I.77.2, resp.) for in that case matter would be exactly as simple as God, who is his own potency. Some medium, therefore, comes in between matter and the soul and any other form.

On the contrary (1), there is this passage in the Book of Church Doctrine: neither do we say that there are two souls in man, one an animal soul which gives life to the body, the other a spiritual soul which subserves reason. (Gennadius of Marseilles, Book of Ecclesiastical Dogmas, bk. 1, ch. 15 (PL 42:1216; 58:984).) From this we argue as follows: just as man belongs to the genus “animal,” so he belongs to the genus “animate body,” and “body,” and “substance.” But through that one and the same form which is the soul, he is both man and animal, as is clear from the passage quoted above. By the same reasoning, therefore, through that one and the same form he is given a place in all the higher genera; thus, there does not exist any form in matter prior to the soul.

Furthermore (2), God and the soul differ more widely than do soul and body. But in the mystery of the Incarnation, the Word was united to the soul immediately. Therefore, for all the greater reason can the soul be immediately united to the body.

Furthermore (3), what is intermediate must have something in common with both of the extremes. (Cf. Aristotle, Topics 4.3, 124a6–7; Physics 5.1, 224b30–31; On the Soul 2.11, 424a6–7.) But there cannot be anything which is partly corporeal and partly spiritual. Therefore, there cannot be any medium between soul and body.

Furthermore (4), the Master says in his first distinction of Sentences 2 (Peter Lombard, Sentences, bk. 2, d. 1, ch. 6, para. 3 [10] (PL 192:654).) that the union of the soul with the body is an illustration of that blessed union whereby the beatified soul is conjoined with God. But that conjunction takes place without any medium. Therefore, the former union does also.

Furthermore (5), the Philosopher says in On the Soul 1 (Aristotle, On the Soul 1.6, 411b6–8.) that the body does not hold the soul together, but rather the soul holds the body together; and in the same place the Commentator says that the soul is the cause of the body’s continuity. (Averroes, Commentary on Aristotle’s On the Soul, bk. 1, comm. 90–91; cf. Aristotle, On the Soul 1.3.) But the body’s continuity depends on the substantial form whereby the body is a body. Therefore, the rational soul itself is the form in man whereby the body is a body.

Furthermore (6), the rational soul is more efficacious and more powerful than is the form of a simple element. But from the form of a simple element a simple body possesses whatever it substantially is. Therefore, for all the greater reason does the human body have from the soul whatever it substantially is; and so, there does not exist beforehand any form or any medium.

I answer that the truth of this question depends to some extent on the preceding one. For if the rational soul is united to the body only through virtual contact, like a mover, as some have asserted, nothing would prevent us from saying that there are many intermediates between the soul and the body, and more so between the soul and prime matter. But if it be asserted that the soul is united to the body as a form, it must be said that it is united to the body immediately. For every form, whether substantial or accidental, is united to matter or to a subject. For each individual thing is one on the same basis on which it is a being. (Cf. Aristotle, Metaphysics 4.2, 1003b22–25; 10.2, 1054a188–19.)

Now, each individual thing is actually a being through a form, whether in the case of actual substantial being or in the case of actual accidental being. Hence, every form is an act, and as a consequence it is the reason for the unity whereby a given thing is one. Therefore, just as we cannot say that there is any other medium whereby matter has actual being through its own form, so it cannot be said that there is any other medium uniting a form to matter or to a subject. In consequence of the fact that the soul, then, is the form of the body, there cannot be any medium between the soul and the body. But in consequence of the fact that it is a mover, from this point of view nothing prevents our asserting many media there. For obviously the soul moves the other members of the body through the heart, and also moves the body through the spirit. (Aristotle, On the Motion of Animals, ch. 10, 703a4–b2; On the Parts of Animals 3.4, 666a11–13.)

But then there is still a doubt about what is the proper subject of the soul, which is related to it as matter is to form. For on this point there are two opinions. Some say that there are many substantial forms in the same individual, and that one of these is the substrate of another; (Aristotle, On the Soul 2.2, 413b27–29; cf. Plato, Timaeus 69c–72b.) and on this view prime matter is not the immediate subject of the ultimate substantial form, but underlies it, with intermediate forms acting as media, so that matter itself, viewed as subject of a form, is the proximate subject of the second form; and so on down to the ultimate form. Thus, then, the proximate subject of the rational soul is the body perfected by the sensitive soul, and to this latter is united the rational soul as a form. The other opinion is that in one individual there is but one substantial form; (This opinion is that which is found in Aristotle, On the Soul 1.5, 411b6–27.) and on this view, it is necessary to say that through the substantial form, which is the human soul, this individual has not only “being man,” but “being animal,” and “being alive,” and “being body,” and “substance,” and “being.” Thus, in this particular man no other substantial form is prior to the human soul, and consequently neither is any accidental form, because in that case one would have to say that prime matter is first perfected through an accidental form rather than through the substantial form, which is impossible. For every accident must be grounded on some substance.

Now the diversity of these two opinions proceeds from the fact that some, in order to investigate the truths of nature, have taken as their starting point intelligible essences, and this was characteristic of the Platonists; whereas some began with sensible things, and this was characteristic of the philosophy of Aristotle, as Simplicius says in his Commentary on the Categories. (Simplicius, Commentary on Aristotle’s Categories, preface.) The Platonists envisaged a definite order of genera and species, and held that the higher can always be understood apart from the lower, as, for instance, “man” apart from “this man,” and “animal” apart from “man,” and so on. (Cf. Boethius, Commentary on Porphyry’s Isagoge, bk. 1, cc. 10–11 (CSEL 48:163, 166–67; PL 64:84–86A).) They thought also that whatever is abstract in the intellect is abstract in reality; otherwise, it seemed to them that the abstracting intellect would be false or futile, if there were no abstract thing corresponding to it. On this account, they also believed that mathematical objects exist apart from sensible things, (Cf. Aristotle, Metaphysics 1.6, 987b14–18; Physics 2.3, 193b35–194a1.) because they are understood apart from them. Hence, they asserted “man in the abstract” apart from “these men,” and so on up to “being,” and “one,” and “good,” which they asserted as the highest virtue of things. (Cf. Aristotle, Nicomachean Ethics 1.6, 1096a22–23; Macrobius, Commentary on the Dream of Scipio, bk. 1, ch. 1, paras. 14–15; bk. 1, ch. 6, paras. 7–8; Augustine, City of God, bk. 8, ch. 8 (PL 41:233; CCSL 47:225).) For they saw that the lower is always more particular than what is above it, and that the nature of the higher is participated by the lower. Now, that which participates serves as the material element for that which is participated; hence, they asserted that among abstract things the more universal a thing is, the more it is something formal. (Proclus, Elements of Theology, proposition 24.)

But some, starting out along the same road, asserted on the contrary that the more universal a form is, the more material it is. This is the position of Avicebron in his book Fountain of Life. (Avicebron, Fountain of Life, tract. 4, nn. 3, 5; tract. 5, n. 34; tract. 2, n. 2.) He asserted a prime matter without any form which he called universal matter, and he said that it is common to spiritual and corporeal substances. And to it, he said, there is added a universal form which is the form of substance. Now, matter thus existing under the form of substance, he said, receives in a part of itself the form of corporeity, while another part of it which pertains to spiritual substances remains without a form of this sort. And so, he proceeded to assert in matter one form under another according to the order of genera and species, down to the ultimate specific species. And this position, although it seems to disagree with the first, nevertheless in actual truth agrees with it and is a consequence of it. For the Platonists asserted that the more universal and the more formal a cause is, the more remote is its perfection in a given individual. Hence, as an effect of the first abstract, that is, of the good, they put down prime matter, in order to have a primary subject corresponding to the supreme agent; and thus, as according to the order of abstract causes and forms that have a share in matter, just as a more universal abstract is more formal, so a more universal participated form is more material. (Cf. Proclus, Elements of Theology, proposition 71.)

But this position, according to the true principles of philosophy which Aristotle considered, is an impossible one. In the first place, this is because no individual instance of substance would be “one” in an unqualified sense. For a thing that is one in an unqualified sense does not come into being from two acts, but from potency and act inasmuch as that which is in potency comes into being actually. And on this account, “white man” is not one in an unqualified sense, but “two-footed animal” is one in an unqualified sense, because the very thing which is animal is two-footed. But if “animal” were something in isolation, and if “two-footed” were something in isolation, “man” would not be one but several, as the Philosopher argues in Metaphysics 3 and 8. (Aristotle, Metaphysics 3.4, 999b25; 7.12, 1037b13–21; 8.6, 1045a14–16.) It is obvious, therefore, that if there were a manifold of many substantial forms in one individual instance of substance, the individual instance of substance would not be one in an unqualified sense, but in a qualified sense, like “white man.”

Second, it is because the account of an accident consists in the fact that it is in a subject, yet in this sense, that by a subject is meant an actual being and not one merely in potency, and in this sense a substantial form is not in a subject but in matter. Whenever there is a form, therefore, of which some actual being is a substrate in any sense, that form is an accident. Now it is obvious that any substantial form, whatever it may be, makes a being actual and is a constituent thereof; (Cf. Aquinas, Disputed Questions on the Soul, q. 9, resp.; Aristotle, Posterior Analytics 1.4, 73b7; Physics 1.7, 191a12.) hence, it follows that only the first form which comes to matter is substantial, whereas all those that come later are accidental. (Cf. Aquinas, Disputed Questions on the Soul, q. 9, resp.) This is not ruled out by what some say, that the first form is in potency to the second form. For every subject is related to its own accident as potency is to act. Besides, a form of a body which would bestow capacity for life would be more complete than one which did not; hence, if the form of a non-living body makes that body to be an actual subject, much more does the form of a body that has life in potency make that body to be an actual subject. Thus, the soul would be a form in a subject, which is the account of an accident.

Third, because it would follow that in the acquiring of the last form, there would be generation not in an unqualified sense but in a qualified sense only. Since generation is a changing over from non-being into actual being, a thing is generated in an unqualified sense when it becomes a being, unqualifiedly speaking, from non-being in an unqualified sense. Now a thing which is already in existence as an actual being cannot become a being in an unqualified sense, but it can become “this particular being,” as, for instance, “white being” or “large being,” and this is becoming in a qualified sense.

Since, then, it is the preceding form in matter which produces actual being, a subsequent form will not produce actual being in an unqualified sense, but “being this particular thing,” as, for instance, “being man” or “being ass” or “being plant”; and so, there will not be generation in an unqualified sense. On this account, all the ancients who asserted that prime matter is actually something, such as fire or air or water or something in between, said that becoming was nothing but change. (Aristotle, Physics 1.4, 187a27–30.) Aristotle solves their difficulty by asserting that matter exists only in potency, (Aristotle, Metaphysics 8.1, 1042a26–27.) and he says that it is the subject of generation and corruption in an unqualified sense. (Aristotle, On Generation and Corruption 1.1, 314b1–4.) Because matter is never denuded of all form, (Cf. SCG II.33.) on this account whenever it receives one form it loses another, and vice versa. Therefore, the generation of one thing always occurs with the corruption of another, and conversely. (Cf. Aristotle, Metaphysics 2.2, 994b5–6; On Generation and Corruption 1.3, 318a23–25.)

Thus, therefore, we say that in “this man” there is no other substantial form than the rational soul, and that by it man is not only man, but animal, and living being, and body, and substance, and being. This can be thought out in the following way. For the form is a likeness of the agent in the matter.

Now, in the case of active and functioning powers, what we find is this, that the higher a power is, the more things does it include within itself, not in composite fashion but as a unit. Thus, for instance, as a single power the common sense extends itself to all sense-objects, which the special senses apprehend as different powers.

Now, it is characteristic of a more perfect agent to produce a more perfect form. Hence, a more perfect form does by means of one thing all that lower forms do by means of different things, and still more: for example, if the form of non-living body confers on matter “actual being” and “being a body,” the form of plant will confer on it this too, and “life” besides; and the sensitive soul will confer this too, and besides it will confer “sensitive being”; and the rational soul will also confer this and besides it will confer “rational being.” For this is the way in which the forms of natural things are found to differ in the order of increasing perfection, as is clear to anyone who looks at all the genera and species of natural things; and on this account the species are compared to numbers, as is said in Metaphysics 8, (Aristotle, Metaphysics 8.3, 1043b33; cf. On the Generation of Animals 2.3, 736b27–28.) the species of which are made different through adding and subtracting one.

And hence, Aristotle also says in On the Soul 2, (Aristotle, On the Soul 2.3, 414b28–31.) the vegetative is in the sensitive, and the sensitive is in the intellectual, as a triangle is in a quadrilateral and a quadrilateral in a pentagon. For a pentagon virtually contains a quadrilateral, since it has this and still more; it is not that something proper to a quadrilateral and something proper to a pentagon exists outside the pentagon, as though there were two figures. So also the intellectual soul virtually contains the sensitive soul, because it has this and still more, yet not in such a way that there are two souls. Now if we were to say that the intellectual soul differed essentially from the sensitive soul in man, no reason could be given for the union of the intellectual soul with the body, since no activity proper to the intellectual soul takes place through a corporeal organ.

Reply Obj. 1: The quotation from Dionysius must be understood as referring to efficient causes, not to formal causes. (Pseudo-Dionysius, The Celestial Hierarchy, ch. 13, para. 3 (PG 3:302).)

Reply Obj. 2: Since the most perfect form imparts everything which the more imperfect forms impart and still more, matter, according as it is perfected by this form in the same kind of perfection wherein it is perfected by more imperfect forms, is considered as proper matter in relation to that kind of perfection which the more perfect form adds over and above the others. Yet this is in such a way that this distinction among forms is not understood as something based on their essence, but only as something based on their intelligible concept. Thus, therefore, matter itself, according as it is understood to be perfect in corporeal being capable of receiving life, is the proper subject of the soul.

Reply Obj. 3: Since “animal” is that which is really “man,” the distinction of animal nature from man is not based on a real diversity of forms as though there were one form whereby the being is animal, and another superadded form whereby it is man. But this distinction is based on intelligible concepts. For according as the body is understood as perfected in sensible being by the soul, in this sense it is related to the ultimate perfection, which comes from the rational soul as such, as a material element is related to a formal element. For since genus and species signify certain conceptual entities, a real distinction of forms is not needed for the distinction between a species and a genus but only a mental distinction.

Reply Obj. 4: The soul moves the body through knowledge and appetite. However, the sensitive and the appetitive power in an animal have a definite organ, and, thus, the movement of the animal originates in that organ which is the heart, according to Aristotle. (Aristotle, On the Generation of Animals 2.6, 742a34, 743b25–26; On the Parts of Animals 3.3, 665a11; On the Motion of Animals 1.10, 703a4–15.) Thus, then, one part of the animal is what does the moving, and the other is the part that is moved, so that the moving part may be taken to be the primary organ of the appetitive soul, and the remainder of the body is what is moved. But because in man the moving is done by the will and the intellect, which are not acts of any organ, the thing that does the moving will be the soul itself, considered on its intellectual side, whereas the moved thing will be the body, considered as something which is perfected by that soul in corporeal being. (Cf. Aquinas, Disputed Questions on the Soul, q. 9, ad 6.)

Reply Obj. 5: In the Incarnation of the Word, the soul is set down as an intermediary between the Word and the flesh, not of necessity but because of fitness; hence also, when the soul was separated from the body at the death of Christ, the Word remained immediately united to the flesh.

Reply Obj. 6: That book is not Augustine’s, nor is it very authentic, and in this quotation the language is rather inexact. For both things pertain to the soul, both the imagination and the sense-appetite; nevertheless, the sense-appetite is said to be connected with the flesh, insofar as it is an appetite for things pertaining to the body, whereas the imagination is said to be connected with the soul, insofar as in it there are likenesses of bodies apart from bodies. Now these are said to be intermediate between the soul and the flesh, not considering the soul as the form of the body, but considering it as the mover.

Reply Obj. 7: The management of the body pertains to the soul insofar as it is the mover, not insofar as it is the form. And although those things by which the soul manages the body are necessary for the soul’s being in the body, as the proper dispositions of this sort of matter, nevertheless it does not follow from this that the account of the management and of the formal union is the same. For just as the soul, which is the mover and the form, is the same soul in substance, but is different in account, so also the things which are necessary for the formal union and for the management are the same things, although not considered from the same point of view.

Reply Obj. 8: The fact that the soul differs from the body as what is corruptible from what is incorruptible does not exclude its being the form of the body, as is clear from what was said above; (See above: a. 2, ad 16.) hence, it follows that it is united immediately to the body.

Reply Obj. 9: The soul is said to be united to the body through the spirit, insofar as it is the mover, because that which is moved first by the soul in the body is the spirit, as Aristotle says in his book On the Motion of Animals; (Aristotle, On the Motion of Animals 1.10, 703a7–18.) yet that book too is not very authoritative.

Reply Obj. 10: If any two things are essentially different in such a way that each has the complete nature of its own species, they cannot be united except through some binding and uniting medium. Now, the soul and the body are not of this sort, since they are both naturally a part of man, but they are related to each other as matter is to form, and their union is immediate, as has been shown. (Above: resp.)

Reply Obj. 11: The soul is united to the body not merely in order to be perfected as regards understanding through phantasms, but also as regards its specific nature and as regards the other activities which it exercises through the body. Nevertheless, even granting that the soul is united to the body merely for the sake of understanding through phantasms, it would not follow that the union would take place through the medium of a phantasm. For the soul is united to the body for understanding in this sense, that through it man may understand, and this would not be the case if the union took place through phantasms, as was shown above.

Reply Obj. 12: The body, before it receives a soul, has some form; however, that form does not remain when the soul comes. For the coming of the soul takes place through a kind of generation, and the generation of one thing does not occur without the corruption of the other. Thus, for instance, when the form of fire is received in the matter of air, the form of air ceases to be in it actually and remains in potency only.

Nor must it be said that the form comes into being or is corrupted, because coming into being and being corrupted are characteristics of that which has actual being, and actual being does not belong to a form as to something that exists, but as to that whereby something is. And hence, too, nothing but the composite is said to come into being, insofar as it is brought from potency into act.

Reply Obj. 13: In the embryo certain vital functions are manifest. But some have said that such functions come from the soul of the mother; (Cf. Aristotle, On the Generation of Animals 2.1, 733b26–30.) but this is impossible because it is in the account of vital functions that they come from an intrinsic principle which is the soul. On the other hand, some have said that from the outset the vegetative soul is present, and that same soul, when it is further perfected, becomes the sensitive soul, and at length becomes the intellectual soul, but through the action of an outside agent which is God. (See Avicebron, The Fountain of Life, tract. 2, n. 6.) But this is impossible: first, because it would follow that a substantial form is susceptible of degrees and that generation is a continuous movement; second, because it would follow that the rational soul is corruptible, so long as it is asserted that the foundation of the rational soul is a vegetative and sensitive substance. (Cf. ST I.118.2, ad 2.) Now it cannot be said that there are three souls in one man, as has been shown. The only thing left to say is that in the generation of man or of animal, there are many generations and corruptions succeeding one another reciprocally, for when a more perfect form comes the less perfect form fades away. Thus, although in the embryo there is first the vegetative soul only, when it has attained a greater perfection the imperfect form is taken away, and the more perfect form takes its place, that is, a soul which is vegetative and sensitive simultaneously. When the last departs, there comes in the most complete ultimate form, which is the rational soul.

Reply Obj. 14: A mathematical body is called an abstract body. Hence, to say that a mathematical body exists in sensible things is to say two opposite things at the same time, as Aristotle argues in Metaphysics 3 (Aristotle, Metaphysics 3.2, 998a13–14.) against certain Platonists who make this assertion. Yet it does not follow that abstraction is falsification, if a mathematical body exists in the intellect only, because the abstracting intellect does not understand that some body exists which is not in sensible things, but rather understands it while not understanding sensible things. Thus, for instance, if someone understands “man” while not understanding his risibility, he is not falsifying; but he would be falsifying if he thought “man is not a risible being.” I say, nevertheless, that if “mathematical body” were in “sensible body,” then since “mathematical body” has dimensions, it pertains only to the genus of quantity. Hence, no substantial form would be needed. But “body” which is in the genus of substance has a substantial form which is called “corporeity,” which is not three dimensions, but is any substantial form whatever from which the three dimensions follow in matter, and this form in fire is “fireness,” in the animal the sensitive soul, and in man the intellectual soul.

Reply Obj. 15: The parts of a definition are formal or specific parts, not because of a real distinction between forms, but on the basis of a mental distinction, as has been said. (Above: ad 3.)

Reply Obj. 16: Although the soul does not have corporeity in act, yet it has it virtually, just as the sun has heat.

Reply Obj. 17: That order upon which the Commentator touches is a conceptual order only. (Averroes, Commentary on Aristotle’s Metaphysics, bk. 1, comm. 17.) For matter is understood to be perfected by a universal form before it is understood to be perfected by a special form, just as being is understood as something prior to living being, living being prior to animal, and animal prior to man.

Reply Obj. 18: Any generic or specific actual being whatever is the thing of which the proper accidents of that genus or species are a consequence. And hence, when matter is already understood to be perfect in the genus which is “body,” it is quite possible to understand therein dimensions, which are the proper accidents of this genus; in this way, the different elementary forms follow one after the other in matter, according to its different parts, in an intelligible order.

Reply Obj. 19: Heat that is the same in species is in fire and in air, because any quality is especially attributed to one element in which it exists perfectly, and is attributed concomitantly or derivatively to another element, yet in a more imperfect way. When, therefore, “fire” comes into being from “this air,” the heat remains the same in species, but it is augmented; nevertheless, it is not the same in number, because the same subject does not persist. Nor does this tend to create a difficulty as regards change, since the heat goes out of being in an accidental way, as a result of the subject’s passing away, and not as a result of an opposite agent.

Reply Obj. 20: Matter, when looked at by itself, is related to all forms indifferently; but it is determined to special forms through the power of the mover, as is taught in On Generation and Corruption 2, (Aristotle, On Generation and Corruption 2.9, 335a30–b6.) and corresponding to the intelligible order of forms in matter there is an order of natural agents. For among the heavenly bodies themselves, one is more universally active than another; nor does the more universal agent act apart from inferior agents, but the ultimate proper agent acts in virtue of all the higher agents. Hence different forms are not implanted by different agents in one individual, but there is one form which is implanted by the proximate agent that virtually contains in itself all the preceding forms. Matter, inasmuch as it is considered to be perfected by the account of the more universal form and the consequent accidents, is specialized to the subsequent perfection.

Reply Obj. 21: Although each genus is divided into potency and act, that potency itself which is in the genus of substance is matter, as form is act. Hence, matter does not exist under form through the medium of some other potency.