Article 15 — Whether the soul, when separated from the body, is capable of understanding

Fifteenth, it is asked whether the soul, when separated from the body, is capable of understanding. (Parallel texts: ST I.89.1; II-II.67.2; SCG II.81; On Truth, q. 19, a. 1; Quodlibet III, q. 9, a. 1; In III Sent., d. 31, q. 2, a. 4; In IV Sent., d. 1, q. 1, a. 1.)

It seems that it is not.

a. For no operation proper to the human composite remains in the soul when it exists apart from the body. (How one should correctly divide this first objection is an intricate textual question with no easy solution. The Leonine edition explains these difficulties on pp. 96–98* of its introduction to the Disputed Questions on the Soul (vol. 24.1). In brief, some manuscripts omitted the text from a. through b. (nulla enim through to intellectivam), beginning the first objection instead at c. below (sicut dicit Philosophus), for the reason that the prior objections were thought not to have been answered below. However, besides the fact that the Leonine edition considers the text to be authentic, it also argues that the reply to the first objection is actually a response to what is here labeled as Objection 1.)* Now understanding is an operation of the composite; for the Philosopher says in On the Soul 1 that to say that the soul understands is like saying that it weaves or builds. (Aristotle, On the Soul 1.4, 408b11–13; cf. Aquinas, In IV Sent., d. 50, q. 1, a. 1; On Truth, q. 19, a. 1, obj. 1.) Therefore, the act of understanding does not remain in the soul when it exists in separation from the body.

Obj. 1: Further, the Philosopher states in On the Soul 3 that understanding in no way takes place without a phantasm. (Aristotle, On the Soul 3.7, 431a14–17.) Now since phantasms exist in the sense organs, they cannot exist in the separated soul. Hence, the soul does not understand when it is separated from the body.

b. But it might be said that the Philosopher is speaking of the soul inasmuch as it is united to the body, and not of the separated soul.

On the contrary, the separated soul can understand only by means of its intellective faculty.

c. Furthermore, understanding is either a form of imagination or is impossible without imagination, as the Philosopher says in On the Soul 1. (Aristotle, On the Soul 1.1, 403a8–9.) But the imagination does not exist without the body. Therefore, neither is there any understanding without the body. Consequently, the soul does not understand when it is separated from the body.

Obj. 2: Further, the Philosopher says in On the Soul 3 that the intellect is related to phantasms as sight is to colors. (Aristotle, On the Soul 3.7, 431a16; cf. Aquinas, Commentary on Aristotle’s on the Soul, bk. 1, lect. 2; bk. 3, lect. 6; ST I.76.1, resp.; On Truth, q. 19, a. 1, obj. 4; Averroes, Commentary on Aristotle’s On the Soul, bk. 3, comm. 30.) But sight cannot see without colors. Therefore, the intellect does not understand without the body.

Obj. 3: Further, the Philosopher says in On the Soul 1 that understanding is corrupted when certain things within the body are corrupted, for example, the heart or the natural heat of the body. (Aristotle, On the Soul 1.4, 408b18–25; cf. On Truth, q. 19, a. 1, obj. 7; ST I.89.1, obj. 1.) However, this is what occurs after the soul is separated from the body. Therefore, the soul is incapable of understanding when it is separated from the body.

Obj. 4: But it may be argued that the soul does understand when it is separated from the body, although not by abstracting from phantasms as it does in the present life.

On the contrary, a form is not united to matter for the sake of the matter but for the sake of the form, for the form is the end and the perfection of the matter. Now a form is united to matter for the sake of fulfilling its own proper operation. Hence, a form requires that specific type of matter by which its operation can be carried to completion, just as the form of a saw requires ferrous matter in order to accomplish the work of cutting. Now the soul is the form of the body. Consequently, the soul is united to that specific type of body which is adapted to carrying out the soul’s proper operation. Now the soul’s proper operation consists in understanding. Therefore, if the soul can understand without the body, then the soul is united to the body in vain.

Obj. 5: Further, if the separated soul is capable of understanding, it understands in a more excellent manner when apart from the body than when united to it. For beings which have no need of phantasms in order to understand do so in a more excellent way than we, who understand through the medium of phantasms. (Cf. Aquinas, In III Sent., d. 31, q. 2, a. 4, resp.; On Truth, q. 19, a. 1, resp.; SCG II.81.) Now the good of the soul lies in its act of understanding, for the perfection of every substance consists in its own proper operation. Therefore, if the soul is capable of understanding without the aid of phantasms, when separated from the body, then it would be harmful to the soul to be united to a body and, hence, would not be natural to it.

Obj. 6: Further, powers are diversified by their objects. But the objects of the intellective soul are phantasms, as the Philosopher says in On the Soul 3. (Aristotle, On the Soul 3.7, 431a14.) Therefore, if the intellective soul, when separated from the body, understands without phantasms, it must have powers other than those which it possesses when united to the body. But that is impossible, since the soul’s powers are natural to it and inhere in it inseparably.

Obj. 7: Further, if the separated soul understands, it must understand by means of some power. Now there are only two intellective powers in the soul: the agent intellect and the potential intellect. But it seems that the separated soul cannot understand by means of either of these powers. For the operation of each of them bears on phantasms: the agent intellect renders phantasms actually intelligible, whereas the potential intellect receives the intelligible species abstracted from phantasms. Consequently, it seems that the separated soul is incapable of understanding in any way. (Cf. Aquinas, On Truth, q. 19, a. 1, obj. 6; SCG II.96.)

Obj. 8: Further, there is but one proper operation for one thing, just as there is only one perfection for one perfectible thing. Therefore, if the operation of the soul consists in understanding by receiving intelligible species from phantasms, it seems that understanding without phantasms cannot be the operation of the soul, and thus that it does not understand when separated from the body.

Obj. 9: Further, if the separated soul understands, it must understand by means of something, because understanding takes place when the likeness of the thing understood exists in the one understanding. It cannot be said, however, that the separated soul understands by its own essence. (Cf. Aquinas, On Truth, q. 19, a. 1, obj. 10.) This is true only of God; for his essence, being infinite, possesses in itself from eternity every perfection, and thus is the likeness of all things. Nor can it be said that the separated soul understands through the essence of the thing understood, because in that case it would understand only those things which are in the soul in virtue of its essence alone. (Cf. Aquinas, On Truth, q. 19, a. 1, obj. 10.) Moreover, it seems that the separated soul cannot understand through any species whether innate or concreated, (Cf. ST I.89.1, obj. 3; On Truth, q. 19, a. 1, obj. 11.) for this would apparently be a reversion to Plato’s theory that we are naturally endowed with all knowledge. (Plato, Phaedo 72d7–73c; Euthydemus 293b–294b; 295b–296d.)

Obj. 10: Further, species of this sort seem to be needlessly implanted in the soul because, so long as it remains in the body, the soul cannot understand through them. (Cf. Aquinas, On Truth, q. 19, a. 1, obj. 11.) However, intelligible species seem to have no other purpose than this, that the soul may understand through them.

Obj. 11: Now it may be argued that, considered in itself, the soul is able to understand through innate species but that, as a matter of fact, it is hindered by the body from understanding through them.

On the contrary, the more perfect a thing is in its nature, the more perfect it is in its operation. Now the soul is more perfect in its nature when united to the body than when it is separated from the body, just as every part of a whole is more perfect when it exists in that whole than when separated from it. Therefore, if the soul existing in separation from the body is able to understand through innate species, it is even more capable of understanding through them when united to the body.

Obj. 12: Further, none of the natural properties of a thing are totally impeded by anything which pertains to the nature itself. (Aristotle, On Generation and Corruption 1.7, 324a1–9; Aquinas, On Truth, q. 19, a. 1, obj. 12; Quodlibet III, q. 1, a. 1.) Now it pertains to the very nature of the soul to be united to the body because the soul is the form of the body. Hence, if intelligible species are naturally implanted in the soul, the soul would not be prevented from understanding through them because of its union with the body. But experience shows that the contrary is true.

Obj. 13: Further, though it seems to be the case, it cannot be said that the separated soul understands through species acquired previously when united to the body. For many human souls will remain separated from their bodies and will never acquire any intelligible species of things, as is evident in the case of the souls of children, and especially of infants who are stillborn. Therefore, if separated souls can understand only through species previously acquired, it would follow that not all separated souls would have understanding. (Cf. Aquinas, On Truth, q. 19, a. 1, obj. 10.)

Obj. 14: Further, if the separated soul understands only through species previously acquired, it seems to follow that it could understand only those things which it understood in this life while united to the body. This seems untrue, however, for the separated soul knows many things concerning punishments and rewards which it does not know in this life. (Cf. Aquinas, On Truth, q. 19, a. 1, resp.) Hence, the separated soul does not understand solely through species acquired before its separation from the body.

Obj. 15: Further, the intellect is rendered intelligent in act by the intelligible species existing in it. But the intellect existing in act is understanding in act. Therefore, the intellect in act understands all those things whose intelligible species actually exist in it. Hence, it seems that intelligible species are not retained in the intellect after it ceases to actually understand, and thus that those species through which it is capable of understanding do not remain in the soul after its separation from the body. (Cf. Avicenna, De anima, part 5, ch. 6; Aquinas, Commentary on Aristotle’s On Sense and What Is Sensed, tract. 2, ch. 2; On Truth, q. 19, a. 1, resp.)

Obj. 16: Further, acquired habits give rise to acts similar to those acts by which the habits were acquired, as is evident from the Philosopher’s observation in Ethics 2. (Aristotle, Nicomachean Ethics 2.1, 1103a30–35; 2.2, 1104a27–35; cf. SCG II.73; ST I.89.5, resp.; I.89.6, obj. 3.) For by building, a man becomes a builder, and the man who thus becomes a builder can in turn engage in building. But the intellect acquires intelligible species by turning to phantasms. Hence, it can understand through phantasms only by turning to them. Therefore, when the soul is separated from the body, it cannot understand through acquired species, as seems to be the case.

Obj. 17: Further, it cannot be said that the intellect understands through species infused by some higher substance. (Cf. Aquinas, On Truth, q. 19, a. 1, obj. 13.) For every receptive entity has its own proper agent by which it is naturally disposed to receive that which it receives. Now the human intellect is naturally disposed to receive its species from the senses.

Obj. 18: Further, in the case of those things which are naturally disposed to be caused by inferior agents, the action of a superior agent alone does not suffice to cause them; thus, animals which are disposed by nature to be generated from seed are not found to be generated by the action of the sun alone. Now the human soul by its very nature is disposed to receive species from the senses. The influx of higher substances, therefore, does not alone suffice to account for its reception of intelligible species. (Cf. SCG II.76.)

Obj. 19: Further, an agent should be proportioned to a patient, and an inflowing power to a recipient. But the intelligence of a superior substance is not proportioned to the human intellect, since the former has knowledge which is more universal than ours and which is incomprehensible to us. Therefore, the separated soul cannot understand through species infused by superior substances, as seems to be the case. Consequently, there is no way in which the separated soul can understand anything.

On the contrary (1), understanding is the highest and proper operation of the soul. Hence, if understanding does not belong to the soul without the body, none of its other operations belong to it either. (Cf. John Damascene, On the Orthodox Faith, bk. 2, ch. 23 [ch. 37] (PG 94:950–51).) But if some operation does not belong to the soul without the body, then it is impossible for the soul to exist apart from the body. (Cf. Aristotle, On the Soul 1.1, 403a10–12; ST I.89.1, s.c.) We maintain, however, that the soul does exist when separated from the body. Hence, it is necessary to hold that it understands.

Furthermore (2), those whom Scripture records as having been brought back to life possessed the same knowledge after this event that they had possessed before. Therefore, the knowledge of those things which a man possesses in this life is not taken away from him after death. Consequently, the separated soul can understand through species acquired before death.

Furthermore (3), the likeness of inferior beings is found in superior ones. Thus, mathematicians foretell the future by studying in the heavenly bodies the likeness of things which are done here on earth. (Cf. Isidore of Seville, The Etymologies, bk. 3, ch. 71, para. 39 (PL 82:183, 877).) Now the soul is superior in nature to all corporeal things. Therefore, the likeness of all corporeal things exists in the soul, and in an intelligible mode, because the soul is itself an intellective substance. (Cf. Aristotle, On the Soul 3.4, 429a18; John Damascene, On the Orthodox Faith, bk. 2, ch. 12 [ch. 26] (PG 94:918–30).) Therefore, it is seen that the soul by its very nature is capable of understanding all corporeal things, even when it will exist in separation from the body.

I answer that the fact that our soul in its present condition needs the senses in order to understand is the cause of the difficulty encountered in solving the problem raised in this article. Therefore, to solve this problem, we must consider the various explanations for this need that have been proposed.

For some men, namely, the Platonists, (Cf. Macrobius, Commentary on the Dream of Scipio, bk. 1, ch. 12, nn. 7–10; Boethius, The Consolation of Philosophy, bk. 3, poem 11 (CCSL 94:60; PL 63:775–77); Pseudo-Augustine (Alcher of Clairvaux), The Spirit and the Soul, ch. 1 (PL 40:781).) have maintained that, in order for the soul to understand, it does not need the senses essentially, as though knowledge were caused in us by the senses, but only accidentally inasmuch as our soul is stirred by the senses to recollect things which it knew in a previous existence, and of which it possesses a knowledge naturally endowed. (Plato, Phaedo 66a; 72d7–73c; Meno; Aristotle, Metaphysics 1.6, 987b4–14; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 1; Commentary on Aristotle’s Posterior Analytics, bk. 1, lect. 1.)

To account for this mode of understanding, Plato held that the species of things subsisted apart from them and were actually intelligible entities. He called them “ideas” and maintained that our soul knows and understands by participating in them, and by some kind of infusion. (Cf. SCG II.74; ST I.84.4, resp.) Moreover, according to Plato, the soul, prior to its union with the body, was able to use this knowledge freely, but as a result of that union it was so weighed down by the body, and somehow smothered by it, that it seemed to have forgotten the things it had previously known and of which it had possessed connatural knowledge. (Cf. Aquinas, On Truth, q. 10, a. 6, resp.; q. 18, a. 7, resp.; q. 19, a. 1, resp.) They also maintained that the soul was in some way stimulated by the senses so that it turned back upon itself and recollected those things which it previously knew and of which it had innate knowledge—just as it sometimes happens that our sense experiences are the occasion for our recollecting vividly certain things which we seemed to have forgotten.

This position of Plato on knowledge and on the senses conforms with his position on the generation of natural things. For he held that the forms of natural things, through which each individual is placed in its proper species, result from a participation in the “ideas” aforementioned, so that the sole function of inferior agents is to dispose matter for participation in the separated species. (Cf. Aristotle, Metaphysics 1.6, 987b1–18; 1.6, 991a20–b3; 7.8, 1033b19–1034a8; 12.3, 1071a17–30; Averroes, Commentary on Aristotle’s Metaphysics, bk. 7, comm. 31; bk. 12, comm. 18.)

Now if this theory be adopted, the whole problem with which we are dealing becomes simple and easy. (Cf. ST I.89.1, resp.) For according to this view, the soul does not by its essence require the senses in order to understand; it requires them only accidentally, and this accidental need ceases to exist as soon as the soul is separated from the body. For the body having ceased to weigh upon the soul, the soul will then have no need of the stimulus of sense. (Cf. Wisdom 9:15.) Existing by itself the soul will be, as it were, lightly clad and on the alert for all knowledge.

Now according to this theory, it appears that no explanation can be offered as to why the soul is united to the body. (Cf. ST I.84.4, resp.; On the Power of God, q. 3, a. 10, resp.) For this union is not for the sake of the soul, (According to the Platonic view under consideration.) because when the soul is not united to the body it can still exercise perfectly its own proper operation, whereas its proper operation is impeded by its union with the body. Similarly, according to this view, it cannot be argued that the union of soul and body exists for the sake of the body; for the soul does not exist for the sake of the body, but rather the body for the soul, because the soul is nobler than the body. (Cf. ST I.89.1, resp.) Then, too, it seems incongruous that the soul should suffer a loss in its own operation for the sake of ennobling the body.

It also seems to follow from this view that the union of the soul with the body is not natural, for whatever is natural to a thing does not impede the operation proper to that thing. (Cf. Aquinas, On Truth, q. 19, a. 1, resp.; ST I.84.3, resp.) Hence, if union with a body impeded the soul’s understanding, it would not be natural but contrary to the nature of the soul to be united to a body; and in that case man, who is constituted of a soul united to a body, would not be a natural being, which seems absurd.

Likewise, experience shows that our knowledge is not the result of participation in separated species, but is acquired from the senses, because those who lack one sense lack knowledge of the sensible things apprehended by that sense, just as a person born blind cannot have a knowledge of colors. (Cf. Aristotle, Posterior Analytics 1.18, 81a38; Aquinas, On Truth, q. 19, a. 1, resp.; SCG II.74.)

Now there is another theory according to which the senses are not accidentally serviceable to the human soul in performing its function of understanding, as the theory just dealt with supposes, but essentially; not in order that we may acquire knowledge from the senses, but because the senses dispose the soul for acquiring knowledge from some other source. This is the opinion of Avicenna. (Avicenna, De anima, part 5, ch. 5; Metaphysics, bk. 8, ch. 7; bk. 9, ch. 4.) For Avicenna maintains that there is a certain separate substance which he calls the intellect or the agent intelligence, that the intelligible species through which we understand flow into our intellect from this agent intellect, and that by the operation of the sensitive part, the imagination, and other things of this sort, our intellect is prepared for orientating itself toward the agent intellect and for receiving the influx of intelligible species from it. This theory agrees with Avicenna’s view on the generation of natural things; for he maintains that all substantial forms flow from the agent intellect, and that natural agents only dispose the matter for receiving forms from the agent intellect. (Cf. Avicenna, Metaphysics, bk. 9, cc. 4–5; Aquinas, On Truth, q. 11, a. 1, resp.; SCG II.76.) According to this position, as in the preceding, this question seems to involve little or no difficulty. For if the senses are necessary for understanding only inasmuch as they dispose the soul to receive species from the agent intellect, because our soul is thus orientated toward the latter, then when the soul is separated from the body it will be orientated toward the agent intellect by itself alone, and it will receive intelligible species from that intellect. Thus, the soul will have no need of the senses in order to understand, just as the ship in which a person has crossed the sea is no longer needed by him after the completion of the voyage. (Cf. Aquinas, On Truth, q. 18, a. 8, obj. 4.)

Now it seems to follow from this view that a man immediately acquires all knowledge, both of things which he perceives by his senses and of other things. For if we understand through species which flow into our minds from an agent intellect, and if all that is required for the reception of this infusion is the orientating of our soul toward this intellect, then whenever the soul is so orientated it will be able to receive the infusion of any and every sort of intelligible species; for in that case it cannot be said that the soul is orientated toward the agent intellect with respect to one species and not with respect to another. Thus, a person born blind will, by imagining sounds, be able to acquire a knowledge of colors, or of any other sensible object, which is manifestly false. (Cf. SCG II.74; ST I.84.4, resp.)

It is also evident that we have need of the sensitive powers for understanding, not only in the acquisition of knowledge, but also in the utilization of knowledge already acquired. (Cf. Aquinas, On Truth, q. 18, a. 8, ad 4; On the Power of God, q. 3, a. 9, obj. 23.) For we cannot even reflect upon the things we know without turning to phantasms, although Avicenna himself is of a contrary opinion. (Cf. Avicenna, De anima, part 5, ch. 3.) It is for this reason that, even in reflecting upon things which it knows, the soul is impeded in its operation by injuries to the organs of the sensitive powers whereby the phantasms are retained and apprehended. (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 7; On Truth, q. 10, a. 6, resp.)

It is evident also that we have need of certain phantasms in things divinely revealed to us through the influence of superior substances. (Cf. Aquinas, On Truth, q. 19, a. 1, resp.) Thus, Dionysius says in The Celestial Hierarchy 1 that the divine light cannot shine upon us unless it is screened round about by many sacred veils. (Pseudo-Dionysius, The Celestial Hierarchy, ch. 1, para. 2 (PG 3:121–22).) Now this would not be so if we needed phantasms only to orientate us toward superior substances.

Consequently, a different explanation must be given for the need which the soul has of sensory powers in order to understand. For they are not accidental in the manner of stimuli, as Plato held, nor are they merely dispositive, as Avicenna claimed, but they re-present to the intellective soul its proper object, as the Philosopher says in On the Soul 3, phantasms are to the intellect what sensible things are to sense. (Aristotle, On the Soul 3.7, 431a14; cf. Aquinas, In III Sent., d. 31, q. 2, a. 4, ad 5; Quodlibet VII, q. 5, a. 1, ad 3.) Now just as colors are made actually visible by light, so phantasms are made actually intelligible only by the agent intellect. (Cf. Aristotle, On the Soul 2.7, 418b2.) This agrees with what we hold about the generation of natural things. For as we maintain that superior agents produce natural forms by means of natural agents, so we maintain that the agent intellect produces knowledge in our potential intellect through phantasms rendered actually intelligible by the agent intellect. (Cf. Aquinas, On Truth, q. 11, a. 1, resp.; SCG II.76.) The question whether the agent intellect is a separate substance, as some held, or a light in which our soul participates in the manner of superior substances, has no bearing on this last point.

Now, according to this latter theory, it seems even more difficult to see how the separated soul can understand. For, on that hypothesis, there will be no phantasms requiring corporeal organs for their apprehension and retention. (Cf. Avicenna, De anima, part 1, ch. 5; part 3, ch. 8.) Yet if these be removed, it is seen that the soul cannot understand, just as the faculty of sight cannot function in the absence of colors.

Now in order to solve this problem, (Cf. ST I.89.1, resp.) the fact must be borne in mind that the soul, being lowest in the order of intellectual substances, participates in intellectual light or in intellectual nature in the lowest and weakest measure. For in the first intelligence, namely, God, intellectual nature is so powerful that he understands all things through one intelligible form, namely, his own essence. (Cf. Aquinas, On Truth, q. 2, a. 3, ad 3; SCG II.98; ST I.89.1, resp.; Commentary on the Book of Causes, proposition 10.) Inferior intellectual substances, on the other hand, understand through many species; and the higher each of these substances is, the fewer forms it possesses, and the more potent is its faculty of understanding all things through those few forms.

However, even if an inferior intellectual substance possessed forms equally as universal as those of a superior substance, its knowledge would still remain incomplete, since it does not have so great a power of understanding, because that inferior intellectual substance would only know things universally, (Cf. ST I.89.1, resp.) and, from the few universal forms it apprehends, it could not bring its knowledge to bear on singulars.

Therefore, if the human soul, which is lowest in the order of intellectual substances and hence possesses the least intellectual power of them all, received forms abstractly and universally, as separate substances do, then it would have a most imperfect kind of knowledge, that of knowing things in the universal and indistinctly. (Cf. ST I.89.1, resp.)

Hence, in order that the soul’s knowledge may be perfect in its kind and bear directly upon singulars, the soul must acquire a knowledge of truth from singular things. (Cf. ST I.89.1, resp.) However, the light of the agent intellect is necessary in order that those things may be received in the soul and may exist there in a higher mode than that in which they exist materially. Hence, it was necessary that the soul be united to a body for the perfection of its intellectual operation. (Cf. Aquinas, In III Sent., d. 31, q. 2, a. 4, resp.; ST I.89.1, resp.)

It is undoubtedly true, however, that bodily movements and the activity of the senses prevent the soul from receiving infused knowledge from separate substances. (Cf. Avicenna, De anima, part 5, ch. 5; Wisdom 9:15.) It is for this reason that certain things are revealed to persons during sleep, and to those who have momentarily lost their senses. (Cf. Aristotle, On Sleep and Sleeplessness, ch. 2, 464a13–27; Avicenna, De anima, part 4, ch. 2; cf. Aquinas, In II Sent., d. 7, q. 2, a. 2, resp.; On Truth, q. 8, a. 12, ad 3; ST I.86.4, ad 2.) Therefore, when the soul shall be separated completely from the body, it will be able to receive infused knowledge from superior substances more fully because, thanks to such knowledge, it will be able to understand without a phantasm, which otherwise it cannot do. (Cf. Avicenna, De anima, part 5, ch. 6; Aquinas, In III Sent., d. 31, q. 2, a. 4, ad 5; On Truth, q. 19, a. 1, resp.; SCG II.81.) Nevertheless, an influx of this sort will not produce knowledge as perfect and as directly related to singulars as the knowledge which we acquire here below through the senses, though a much more perfect knowledge will be had in addition to this natural influx by those souls that will enjoy the influx of a supernatural light by which they will know all things most fully and will see God himself. (Cf. Aquinas, In III Sent., d. 31, q. 2, a. 4; On Truth, q. 19, a. 1, resp.; SCG II.81.) Moreover, separated souls will have a determinate knowledge of those things which they had previously known here below, and whose intelligible species they retain in themselves. (Cf. SCG II.81.)

Reply Obj. 1: The Philosopher is speaking of the intellectual operation of the soul so far as the soul is united to the body; for in that state the soul does not understand without a phantasm, as has been explained.

Reply Obj. 2: In its present state of union with the body, the soul does not participate in intelligible species flowing from superior substances, but only in intellectual light. Consequently, the soul is in need of phantasms as objects from which it may receive intelligible species. But after its separation from the body, the soul will indeed participate more fully in intelligible species, and, therefore, will have no need of external objects. (Cf. Aquinas, On Truth, q. 19, a. 1, resp.; ST I.89.1, resp.)

Reply Obj. 3: It is clear from what has been said before that the Philosopher refers in this place to the opinion of certain others who held that the intellect has a bodily organ just as a sense faculty does. Now if this were maintained, the separated soul would be entirely incapable of understanding anything. (Cf. ST I.89.1, ad 1.) Or we may reply that the Philosopher is speaking of that mode of understanding which we possess here and now. (Cf. Aquinas, On Truth, q. 19, a. 1, ad 7.)

Reply Obj. 4: The soul is united to the body in virtue of the soul’s operation, which is understanding; this is not because it could in no way understand without the body, but because in the natural order it could not understand perfectly without the body, as has been shown. (Cf. ST I.89.1, resp.; see above: resp.)

Reply Obj. 5: And from this the solution to the fifth is clear.

Reply Obj. 6: Phantasms are objects of the intellect only so far as they are rendered actually intelligible by the light of the agent intellect. (Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 7, n. 794.) Consequently, all actually intelligible species which are received in the intellect, wherever they may come from, will have no other formal object; and it is by their formal objects that the powers of the soul are differentiated.

Reply Obj. 7: The operation of the agent intellect and that of the potential intellect bear on phantasms so long as the soul remains united to the body; but when the soul will be separated from the body, it will receive, through its potential intellect, the species that flow into it from superior substances, and it will have the power of understanding through its agent intellect. (Cf. Aquinas, On Truth, q. 19, a. 1, ad 8.)

Reply Obj. 8: The proper operation of the soul is to understand things that are actually intelligible. Moreover, intellectual operation is not diversified in species because actual intelligibles are received from phantasms or elsewhere.

Reply Obj. 9: The separated soul does not understand things through its own essence, nor through the essences of the things understood, but through species flowing into it from superior substances; nor does it, as the Platonists claimed, understand things from the very beginning of its existence.

Reply Obj. 10: Thus, the reply to the tenth objection is evident.

Reply Obj. 11: If the soul, when united to the body, possessed innate species, it would be able to understand through them, just as it understands through acquired species. (Cf. Aquinas, On Truth, q. 19, a. 1, obj. 11–12.) Now although it is more perfect in its nature when united to the body, nevertheless on account of bodily movements and sense activities, the soul is held in check, so that it cannot be united to superior substances in order to receive infused knowledge from them, as it does when it is separated from the body.

Reply Obj. 12: To understand through infused species is not natural to the soul when united to the body, but only after it has left the body, as we have pointed out.

Reply Obj. 13: Separated souls will indeed be able to understand through species acquired previously while they existed in the body, but not through them alone. They will also understand through infused species, as we have explained.

Reply Obj. 14: Thus, the reply to objection fourteen is evident.

Reply Obj. 15: Intelligible species sometimes exist in the potential intellect only potentially. When that is the case, man knows only potentially, and he thus needs to be made actually knowing either by teaching or by discovery. Sometimes, however, intelligible species exist in the potential intellect in a completely actual way, and when that is the case, it knows actually. Sometimes, however, they exist in it in a mode midway between potency and act, that is to say, as a habit, and when that is the case, the intellect can understand actually whenever it wishes. Moreover, thanks to this mode of existing, acquired intelligible species exist in the potential intellect even when it is not performing acts of understanding.

Reply Obj. 16: As has already been pointed out, an intellectual operation whose actually understood object is received from phantasms does not differ in species from an intellectual operation whose object is derived from some other source. (See above: ad 6.) For the operation of a power receives its difference and species by the formal nature of the object, not by its matter. (Cf. ST I.89.5, resp.; I-II.67.2, resp.) Hence, if the separated soul understands through intelligible species which are retained in the intellect, and which were previously acquired from phantasms, and not by actually turning itself to phantasms, then the operation which results from the species so acquired and the operation by which those species are acquired will not be different in species. (Cf. ST I.89.6, resp., ad 3.)

Reply Obj. 17: The potential intellect is disposed by nature to receive species from phantasms only so far as the phantasms are actualized by the light of the agent intellect, which is a kind of participation of the light of superior substances. (Cf. Aquinas, Commentary on Aristotle’s on the Soul, bk. 3, lect. 1; SCG II.77.) Consequently, the intellect is not prevented from being able to receive species from superior substances. (Cf. Aquinas, On Truth, q. 10, a. 6, resp.; SCG II.81; III.45.)

Reply Obj. 18: In its present state of union with the body, the soul is disposed by nature to acquire knowledge from phantasms, and in this state its knowledge cannot be caused by superior agents alone. But this will be possible when the soul is separated from the body.

Reply Obj. 19: From the fact that the knowledge of separate substances is not proportioned to our soul, it does not follow that our soul is incapable of grasping any knowledge from the influx of those substances, but only that it cannot grasp a perfect and distinct knowledge, as has been explained. (See above: resp.)