And first it is asked whether the human soul can be a form and a particular thing.¹

Now some men have denied that the human soul possesses these two real characteristics belonging to a particular thing by its very nature because they said that the soul is a harmony, as Empedocles did,¹ or a combination of the elements, as Galen did, or something of this kind.² For then the soul will neither be able to subsist of itself, nor will it be a complete thing belonging to a species or genus of substance, but will be a form similar only to other material forms.

But this position is untenable as regards the vegetative soul, whose operations necessarily require some principle surpassing the active and passive qualities of the elements, which play only an instrumental role in nutrition and growth, as is proved in On the Soul 2.¹ Moreover, a combination and a harmony do not transcend the elemental qualities. This position is likewise untenable as regards the sensitive soul, whose operations consist in receiving species separated from matter, as is shown in On the Soul 2.² For inasmuch as active and passive qualities are dispositions of matter, they do not transcend matter. Again, this position is even less tenable as regards the rational soul, whose operation consists in understanding, and in abstracting species not only from matter, but from all individuating conditions, this being required for the understanding of universals.³

However, in the case of the rational soul, something of special importance must still be considered because not only does it receive intelligible species without matter and material conditions, but it is also quite impossible for it, in performing its proper operation, to have anything in common with a bodily organ, as though something bodily might be an organ of understanding, just as the eye is the organ of sight, as is proved in On the Soul 3.¹ Thus, the intellective soul, inasmuch as it performs its proper operation without communicating in any way with the body, must act of itself. And because a thing acts so far as it is actual,² the intellective soul must have a complete act of existing in itself, depending in no way on the body.³ For forms whose act of existing depends on matter or on a subject do not operate of themselves. Heat, for instance, does not act, but something hot.

For this reason, the later Greek philosophers came to the conclusion that the intellective part of the soul is a self-subsisting thing. For the Philosopher says that the intellect is a substance, and is not corrupted.¹ The teaching of Plato, who maintains that the soul is incorruptible and subsists of itself, in view of the fact that it moves itself, amounts to the same thing.² For he took “motion” in a broad sense to signify every operation; hence, he understands that the soul moves itself because it moves itself by itself. But elsewhere, Plato maintained that the human soul not only subsists of itself but also has the complete nature of a species.³ For he held that the complete nature of the human species is found in the soul, saying that a man is not a composite of soul and body, but a soul joined to a body in such a way that it is related to the body as a pilot is to a ship, or as one clothed to his clothing.⁴

However, this position is untenable because it is obvious that the soul is the reality which gives life to the body. Moreover, vital activity is the act of existing of living things. Consequently, the soul is that which gives the human body its act of existing. Now a form is of this nature.¹ Therefore, the human soul is the form of the body. But if the soul were in the body as a pilot is in a ship, it would give neither the body nor its parts their specific nature. The contrary of this is seen to be true because when the soul leaves the body, the body’s individual parts retain their original names only in an equivocal sense. For the eye of a dead man, like the eye of a portrait or that of a statue, is called an eye equivocally;² and similarly for the other parts of the body. Furthermore, if the soul were in the body as a pilot in a ship, it would follow that the union of soul and body would be an accidental one. Then death, which brings about their separation, would not be a substantial corruption, which is clearly false. So it follows that the soul is a particular thing, and that it can subsist of itself, not as a thing having a complete species of its own, but as completing the human species by being the form of the body.³ Hence, it likewise follows that it is both a form and a particular thing.

Indeed, this can be shown from the order of natural forms.¹ For we find among the forms of lower bodies that the higher a form is, the more it resembles and approaches higher principles. This can be seen from the proper operation of forms. For the forms of the elements, being lowest and nearest to matter, possess no operation surpassing their active and passive qualities, such as rarefaction and condensation, and the like, which appear to be material dispositions. Over and above these forms are those of the mixed bodies, and these forms have, in addition to the above mentioned operations, a certain activity, consequent upon their species, which they receive from the heavenly bodies. The magnet, for instance, attracts iron not because of its heat or its cold or anything of this sort, but because it shares in the powers of the heavens.² Again, surpassing these forms are the souls of plants, which resemble not only the forms of earthly bodies but also the movers of the heavenly bodies inasmuch as they are principles of a certain motion, themselves being moved. Still higher are brute beasts’ forms, which now resemble a substance moving a heavenly body not only because of the operation whereby they move bodies but also because they are capable of knowledge, although their knowledge is concerned merely with material things and belongs to the material order, for which reason they require bodily organs. Again, over and above these forms, and in the highest place, are human souls, which certainly resemble superior substances with respect to the kind of knowledge they possess because they are capable of knowing immaterial things by their act of understanding. However, human souls differ from superior substances inasmuch as the human soul’s intellective power, by its very nature, must acquire its immaterial knowledge from the knowledge of material things attained through the senses.

Consequently, the human soul’s mode of existing can be known from its operation. For inasmuch as the human soul has an operation transcending the material order, its act of existing transcends the body and does not depend on the body. Indeed, inasmuch as the soul is naturally capable of acquiring immaterial knowledge from material things, evidently its species can be complete only when it is united to a body. For a thing’s species is complete only if it has the things necessary for the proper operation of its species. Consequently, if the human soul, inasmuch as it is united as a form to the body, has an act of existing which transcends the body and does not depend on it, obviously the soul itself is established on the boundary line dividing corporeal from separate substances.¹

[No Reply to Objection 13b is provided.]¹

Second, it is asked whether the human soul, so far as its act of existing is concerned, is separated from the body.¹

However, the triangle is not contained actually in the quadrilateral, but only potentially; nor is the quadrilateral contained actually in the pentagon. Therefore, neither the nutritive nor sensitive part of the soul is contained actually in the intellective. Consequently, since the intellective part of the soul is united to the body only through the intermediary of the nutritive and sensitive parts, because the sensitive and nutritive parts of the soul are not actually contained in the intellective part, the intellective part of the soul will not be united to the body.

By means of this proof we exclude the position of the ancient philosophers,¹ who held that the intellect did not differ from the sensitive powers, as well as the position of those who maintained that the principle by which a man understands is a certain form or power which is united to the body as other material forms or powers are.²

But certain other men, avoiding this position, fall into the opposite error.¹ For they think that the potential intellect is devoid of every sensible nature and that it is not present in the body because it is a certain substance which exists in separation from the body and is in potency to all intelligible forms.

But this position cannot be maintained, because we acquire our knowledge of the potential intellect only so far as a man understands by it. Indeed, this is the way Aristotle obtains his knowledge of it, as is evident from what he says in On the Soul 3 when he begins to discuss the potential intellect: concerning that part of the soul by which the soul knows and perceives . . . it must be considered . . . ;¹ and in another place he says, I speak of the potential intellect by which the soul understands.²

But if the potential intellect were a separate substance, it would be impossible for a man to understand by means of it because, if a substance performs an operation, that operation cannot belong to any other substance than the one performing it. For although one of two substances can be the cause of the other’s operation, as the principal agent is the cause of the activity of the instrument, nevertheless the action of the principal agent is not numerically the same as that of the instrument. For the action of the principal agent consists in moving the instrument, whereas that of the instrument consists in being moved by the principal agent and in moving something else. Consequently, if the potential intellect is a substance existing apart from this or that particular man, it is impossible for the potential intellect’s act of understanding to be the act of any particular man. From this it follows that no man understands anything, because the act of understanding is not attributed to any principle in man except the potential intellect.¹ Hence, the same manner of arguing is opposed to this position and to those who deny its principles, as is evident from Aristotle’s arguments against them in Metaphysics 4.²

Now Averroes, who is a follower of this position, intending to avoid its incongruity, maintained that the potential intellect, although it existed apart from the body, must be united to man through the intermediary of phantasms.¹ For phantasms, as the Philosopher says in On the Soul 3, are related to the potential intellect as sensible things are to sense, and colors to sight.² Thus, an intelligible species has two subjects: one in which it exists with an intelligible mode of existing, and this is the potential intellect; another in which it exists with a real mode of existing, and this subject is the phantasms.³ Therefore,⁴ there is a certain union of the potential intellect with the phantasms inasmuch as an intelligible species exists in a certain manner in each of these subjects; and a man understands through the potential intellect⁵ as a result of this union with the phantasms.⁶

However, this union is still not sufficient to account for man’s knowledge, for a thing is capable of knowing, not because intelligible species are present to it, but because it possesses a cognitive power. Now evidently, from what has been said, intelligible species alone will be present to man, whereas the power of understanding, that is, the potential intellect, exists in complete separation from him. Therefore, it does not follow from the aforesaid union that a man will have what is necessary for understanding, but only that a species or something in that intellect will be understood. This clearly appears to be the case from the simile introduced above. For if phantasms are related to the intellect as colors are to sight, the union of the potential intellect with us through our phantasms will be the same as that of sight with a wall through its colors. Now it does not follow that a wall sees because it has colors, but only that it is seen. Nor, similarly, does it follow that a man will understand because phantasms are present within him, but only that he will be understood.¹

Furthermore, a phantasm is not the subject of an intelligible species inasmuch as the latter is actually understood. On the contrary, an intelligible species is made to be actually understood by abstraction from phantasms. Moreover, the potential intellect is the subject of an intelligible species only inasmuch as an intelligible species is now actually understood and abstracted from phantasms. Therefore, the species existing in the potential intellect and that existing in the phantasms, through which the potential intellect¹ is united to us, are not one and the same.

Furthermore, if anyone understands through intelligible species only when they are understood in act, it follows, according to the aforesaid position, that we are incapable of understanding anything in any way, for then intelligible species would be present to us only inasmuch as they exist in phantasms, and here they are only potentially understood.¹

Consequently, it is evident on the side of our human nature that the above-mentioned position is impossible. This is also apparent from the nature of separate substances. Since these are most perfect, it is impossible for them in their own operations to stand in need of the operations of material things; nor need they be in potency to any things of this kind, for not even the heavenly bodies, which are below the separate substances, require things of this sort. Hence, since the potential intellect is in potency to the species of sensible things, and since its operation may not be completed without phantasms, which depend on our operations, it is impossible and inconceivable for the potential intellect to be one of the separate substances.¹

Consequently, we must say that the potential intellect is a certain faculty or power of the human soul. For although the human soul is a form united to the body, it is not embraced completely by the body as though immersed in it as other material forms are, but transcends the capacity of the whole of corporeal matter. And so far as the soul transcends corporeal matter, the potentiality for intelligibles exists in the soul, and this potentiality belongs to the potential intellect. Certainly the soul, so far as it is united to the body, has operations and powers in common with the body; such, for example, are the powers of the nutritive and sensitive part. Thus, the nature of the potential intellect is as Aristotle proves it to be, for the potential intellect is not a power rooted in any bodily organ.¹ However, a man understands formally by means of it inasmuch as it is rooted in the essence of the human soul, which is the form of man.²

Third, it is asked whether there is one potential intellect, or intellective soul, for all men.¹

Now those maintaining that there is one potential intellect for all men try to avoid the absurdity of this position by pointing to the fact that the intelligible species, on which the perfection of science is based, have a twofold subject, as was shown above, namely, the phantasms themselves and the potential intellect.¹ And they argue that intelligible species are not the same in all men, because phantasms are not the same in all. In fact, as existing in the potential intellect, intelligible species are not multiple. So it is that one man possesses a science which another lacks because he has different phantasms. But this is evidently foolish in view of what has previously been said.² For species are actually intelligible only by being abstracted from phantasms and by existing in the potential intellect. Therefore, diversity of phantasms cannot be the cause of the unity or multiplicity of a perfection having the character of scientific knowledge. Nor do scientific habits exist in some part of the sensitive soul as their subject, as these men claim.³

But an even greater difficulty faces those who maintain that there is one potential intellect for all men. For it is evident that the act of understanding has its origin in the potential intellect as the first principle whereby we understand, just as the operation of sensing has its origin in a sensitive power. And although it was shown above that, if the potential intellect exists apart from man, the act of understanding (which belongs to the potential intellect) cannot be the operation of this or that man,¹ nevertheless, from the hypothesis of one potential intellect for all men, it follows that this or that man understands by the potential intellect’s own act of understanding.

Yet an operation can be multiplied in only two ways: either on the side of the object, or on that of the principle operating.¹ A third way can also be envisaged from the point of view of time, as, for instance, when an operation involves temporal changes. Hence, the act of understanding, which is the operation of the intellect, can be multiplied with respect to objects known so that it is one thing to know a man, another thing to know a horse. The act of understanding can also be multiplied with respect to time, so that to understand what happened yesterday is one act, and to understand what happens today another, if, of course, the operation is not continuous. However, the act of understanding cannot be multiplied respecting the principle operating if there is only one potential intellect.

Therefore, if the potential intellect’s own act of understanding is this or that man’s act of understanding, this man’s act of understanding and that man’s could be different if they were understanding different things. A reason for this can be found in the diversity of phantasms. The act of understanding by different men understanding the same thing, according to the one potential intellect theory, could be multiplied similarly, so that one understands today and another tomorrow. This can also be attributed to the different use of phantasms. But in the case of two men who understand the same thing at the same time, their act of understanding would have to be numerically one and the same, which is clearly impossible.¹ Therefore, it is impossible for the potential intellect, by which we understand formally, to be one and the same for all men.

However, it would be more reasonable to hold that we understand by the potential intellect as an active principle existing in us and causing in us actual understanding. For one mover puts different things into operation. But that different things should act through some one thing formally is absolutely impossible.¹

Moreover, the forms and species of natural things are known through their proper operations. But the proper operation of man, as man, is understanding and reasoning. Hence, the principle of this operation, namely, the intellect, is that whereby man is made to be this species; it cannot be the sensory soul, nor any other power of man. Therefore, if the potential intellect, existing as a separate substance, is one for all men, then all men are made to be the species that they are by one substance existing apart from them. This position is reminiscent of the doctrine of ideas, and labors under the same difficulty.¹

Consequently, it must be said absolutely that there is not one potential intellect for all men, but that there are many intellects, one for each man. And since the intellect is a certain power or capacity of the human soul, it is multiplied according as the substance of the soul itself is multiplied. This multiplication can be considered in the following way: if a thing having a certain common character is multiplied materially, it must be multiplied numerically while remaining the same in species. For instance, flesh and bones belong to the very account of animal. Hence, the distinction between animals, which is based on individual bodily differences, makes them diverse in number, not in species.

Moreover, it is clear from what was said above¹ that the human soul, by its very account, is capable of union with the human body because the human soul is not a complete species in itself but acquires the completion of its species in the composite itself.² Hence, the fact that the soul is capable of being united to this or to that body multiplies the soul in number, not in species, just as this whiteness differs in number from that because it belongs to this or that subject. But the human soul differs from other forms in this way, that its act of existing does not depend on the body. Nor does this individuated act of existing which it has depend on the body;³ for inasmuch as a thing is one, it is undivided in itself and distinct from other things.⁴

But according to Aristotle, the fact that the intellect understands a one-in-many in abstraction from individuating principles is to be attributed to the intellect itself.¹ And though nothing abstract exists in reality, the intellect is not void of any real content, nor is it misrepresentative of things as they are because, of those things which necessarily exist together, one can be truly understood or named without another being understood or named.² But it cannot be truly understood or said of things existing in this way, that one exists without the other.

Thus, whatever exists in an individual which pertains to the nature of its species, and in respect of which it is like other things, can be known and spoken of truly without taking into consideration its individuating principles which distinguish it from all other individuals of the same species. Consequently, by its abstractive power the intellect makes this universal unity itself, not as though it were a unity existing in things themselves, but as an immaterial representation of them.¹

Fourth, it is asked whether it is necessary to admit that an agent intellect exists.¹

Moreover, it produces these intelligibles by abstracting them from matter and from material conditions which are the principles of individuation.¹ And since the nature as such of the species does not possess these principles by which the nature is given a multiple existence among different things, because individuating principles of this sort are distinct from the account itself,² the intellect will be able to receive this account apart from all material conditions and consequently will receive it as a unity. For the same reason, the intellect receives the nature of a genus by abstracting from specific differences, so that it is a one-in-many and common to many species.

However, if universals subsisted in reality in virtue of themselves, as the Platonists maintained,¹ it would not be necessary to admit than an agent intellect exists, because things which are intelligible in virtue of their own nature move the potential intellect. Therefore, it appears that Aristotle was led by this necessity to posit an agent intellect, because he did not agree with the opinion of Plato on the question of ideas.

Nevertheless, there are some subsistent things in the real order which are actual intelligibles in virtue of themselves; the immaterial substances, for instance, are of this nature.¹ However, the potential intellect cannot attain a knowledge of these immediately but acquires its knowledge of them through what it abstracts from material and sensible things.²

However, if we speak of the intellect in act of the teacher, it is evident that when the teacher causes knowledge in one who is learning, he does not act as an interior agent, but as an external administrator, just as, in the production of health, a physician acts as an external administrator, whereas the nature of the patient acts as an interior agent.¹

Fifth, it is asked whether there is one separately existing agent intellect for all men.¹

But this position, if anyone examines it carefully, is seen to be implausible, because the superior substances are related to our souls as heavenly bodies are to inferior bodies. For, as the powers of superior bodies are certain universal active principles in relation to inferior bodies, so also the divine power and the powers of different secondary substances—if the latter do influence us in any way—are related to our souls as universal active principles. However, we see that there must exist in addition to the universal active principles of the heavenly bodies certain particular active principles which are powers of inferior bodies, limited to the proper operation of each and every one of them. This is particularly necessary in the case of perfect animals because certain imperfect animals are found for whose production the power of a heavenly body suffices, as is evident in the case of animals generated from decomposed matter.¹ However, in the generation of perfect animals, a special power is also required in addition to the heavenly power, and this power is present in the seed.² Therefore, since intellectual operation is the most perfect thing existing in the entire order of inferior bodies, we need, in addition to universal active principles—namely, the power of God enlightening us, or the powers of any other separate substance³—an active principle existing within us by which we are enabled to understand actually. This power is the agent intellect.

We must also consider this, that, if the agent intellect is held to exist as a separate substance along with God, a consequence repugnant to our faith will follow,¹ namely, that our ultimate perfection and happiness consists not in a certain union of our soul with God, as the Gospel teaches, saying, this is eternal life, that they know thee, the only true God (John 17:3), but with some other separate substance.² For it is evident that man’s ultimate beatitude or happiness depends upon his noblest operation, understanding, which operation, in order to be fully completed, requires the union of our intellect³ with its active principle. For, indeed, anything passive in any way whatever is perfected only when joined with the proper active principle which is the cause of its perfection.⁴ Therefore, those maintaining that the agent intellect is a substance existing apart from matter say that man’s ultimate happiness consists in being able to know the agent intellect.

Moreover, if we give the matter further careful consideration, we will find that the agent intellect cannot be a separate substance for the same reason that the potential intellect cannot be, as was shown above.¹ For, as the operation of the potential intellect consists in receiving intelligible species, so also does the proper operation of the agent intellect consist in abstracting them, for it makes them actually intelligible in this way. Now we experience both of these operations in ourselves because we receive our intelligible species and abstract them as well.² However, in anything that operates there must be some formal principle whereby it operates formally, because a thing cannot operate formally through something that possesses existence distinct from itself. But, although the motive principle of an activity is separate from the thing which it causes, nevertheless there must be some intrinsic principle whereby a thing operates formally, whether it be a form or some sort of impression. Therefore, there must exist within us a formal principle through which we receive intelligible species, and one whereby we abstract them. These principles are called the possible and the agent intellect, respectively. Consequently, each exists within us. Moreover, the formal intrinsic existence in us of the agent intellect is not accounted for simply by the fact that the action of the agent intellect, namely, the abstracting of intelligible species, is carried out through phantasms illumined in us by its action. For every object produced by art is the effect of the action of an artificer, the agent intellect being related to the phantasms illumined by it as an artificer is to the things made by his art.³

Now it is not difficult to see how both of these can be present in one and the same substance of the soul, that is, the potential intellect, which is in potency to all intelligible objects, and the agent intellect which makes them actually intelligible;¹ because it is not impossible for a thing to be in potency and in act with respect to one and the same thing in different ways. Therefore, if we consider the phantasms themselves in relation to the human soul, in one respect they are found to be in potency, inasmuch as they are not abstracted from individuating conditions, although capable of being abstracted. In another respect they are found to be in act in relation to the soul, namely, inasmuch as they are likenesses of determinate things. Therefore, potentiality with respect to phantasms must be found within our soul so far as these phantasms are representative of determinate things. This belongs to the potential intellect, which is, by its very nature, in potency to all intelligible objects, but is actuated by this or that object through species abstracted from phantasms. Our soul must also possess some active immaterial power that abstracts the phantasms themselves from material individuating conditions. This belongs to the agent intellect, so that it is, as it were, a power participated from the superior substance, God. Hence, the Philosopher says that the agent intellect is like a certain habit and light.² In the Psalms it is also said, lift up the light of thy countenance upon us, O Lord (Ps 4:6 [7]). Something resembling this in a certain degree is apparent in animals who see by night.³ The pupils of their eyes are in potency to every color inasmuch as they have no one determinate color actually but make colors actually visible in some way by means of a certain innate light.⁴

Indeed, some men thought that the agent intellect does not differ from our habit of indemonstrable principles.¹ But this cannot be the case, because we certainly know indemonstrable principles by abstracting them from singulars, as the Philosopher teaches in Posterior Analytics 2.² Consequently, the agent intellect must exist prior to the habit of first indemonstrable principles in order to be the cause of it. Indeed, the principles themselves are related to the agent intellect as certain of its instruments, because the intellect makes things actually intelligible by means of such principles.

He first distinguishes it in relation to the potential intellect because the potential intellect and the thing known are not one and the same. However, the intellect or science-in-act is the same as the thing actually known. Aristotle had said the same thing about sense, namely, that sense and what is potentially sensible differ from each other, but that sense and what is actually sensed are one and the same.¹

Second, he shows how the potential intellect is related to the intellect-in-act, because in one and the same individual, intellect in potency precedes intellect-in-act.¹ However, it does not precede it absolutely, for he very often uses this manner of speaking concerning things that pass from potentiality to actuality.² Then he makes the statement quoted above, in which he shows the difference between the potential intellect and the intellect-in-act, because the potential intellect sometimes understands and sometimes does not, which cannot be said of the intellect-in-act.³ He points out a similar difference in Physics 3 between causes in potency and causes in act.⁴

Sixth, it is asked whether the soul is composed of matter and form.¹

Now the weakness of this argument becomes apparent if we consider that to receive, to be a subject, and other things of this sort, are not found in the soul and in prime matter in the same specific way.¹ For prime matter is actuated by means of change and motion, and since every change and motion may be reduced to local motion, as the primary and most universal type of motion, as is proved in Physics 8, it follows that matter is present only in those things in which there is potency to place.²

Moreover, things of this kind, which are circumscribed by place alone, are corporeal.¹ Hence, in accordance with the way in which the philosophers have spoken about matter, matter is present only in corporeal things; unless, of course, someone wishes to employ matter in an equivocal sense.² The soul, however, does not receive something by means of motion and change, but, on the contrary, by being separated from motion and from movable things. Accordingly, it is said in Physics 7 that the soul becomes cognitive and possesses prudence when at rest.³ Wherefore the Philosopher also states in On the Soul that understanding is referred to as a passion but is a passion of a different nature from that present in corporeal things.⁴ Therefore, if anyone wishes to conclude that the soul is composed of matter because it is receptive or is acted upon, he is clearly deceived by an equivocation. Consequently, it is evident that the aforesaid argument is foolish.

Moreover, it can be shown in several ways that this position is impossible. First, for this reason, that when a form accrues to matter, it constitutes a species. Therefore, if the soul is composed of matter and form, a certain species will be established in the natural order as a result of the union itself of the form and matter of the soul. However, a thing which possesses a specific nature in its own right is not united to some other thing in order to constitute a species, unless each is corrupted in some manner, just as, for example, the elements are united in order to constitute the species of the mixed bodies.¹ The soul, therefore, is not united to the body in order to constitute the human species, but the complete human species is comprised of the soul alone. This is clearly false, for if the body does not belong to the human species, it is joined to the soul in an accidental way.

Moreover, it cannot be said, according to this, that the hand is not composed of matter and form because it does not have a complete species of its own, but is a part of a species; for it is evident that the matter of the hand is not perfected separately by its own form, but that there is one form which perfects at the same time the matter of the whole body and that of all its parts. This could not be said of the soul if it were composed of matter and form. For in that case, the matter of the soul would first have to be perfected in the order of nature by its own form, and the body in turn perfected by the soul; unless, perhaps, someone might care to say that the soul’s matter is some part of corporeal matter, which is utterly absurd.

The position of Avicebron is also shown to be impossible for this reason, that in everything composed of matter and form, matter occupies the position of that which receives existence, and not that by which something exists; for this is peculiar to the form alone. Therefore, if the soul is composed of matter and form, it is impossible for the entire soul to be the formal principle which gives to the body its act of existing. The whole soul, therefore, will not be the form of the body, but only a part of the soul will be so. The soul, however, is certainly that entity which is the form of the body. Therefore, the soul is not that thing which was considered to be a composite of matter and form, but the form of it alone.¹

This position is also seen to be impossible for another reason. For if the soul is composed of matter and form, and the body as well, each of them will have its unity in virtue of itself, and then it will be necessary to admit that some third entity exists which unites the soul to the body. Indeed, some of the adherents of the aforesaid position do maintain this. For they say that a soul is united to its body by the instrumentality of light, the vegetative soul by the mediating light of the sidereal heaven, the sensitive soul by the mediating light of the crystalline heaven, and the rational soul by the mediating light of the empyrean heaven. These explanations are entirely fictitious, because the soul must be united to the body without any intermediary, just as act is to potency, as is shown in Metaphysics 8.¹ It becomes evident, then, that the soul cannot be composed of matter and form.

However, act and potency are not excluded from the soul, for potency and act are found not only in immovable things, but in movable things as well; and they are more common here, as the Philosopher points out in Metaphysics 9, because matter itself may not exist in immovable things.¹

Now the manner in which act and potency are found in the soul must be discovered by proceeding from material things to immaterial ones.¹ For we observe three things in substances composed of matter and form, namely, matter, form, and the act of existing itself, the principle of which is the form; for matter receives an act of existing because it receives a form.² Therefore, a thing’s act of existing is the natural effect of the form itself of that thing.

However, the form is not identical with its own act of existing, because the form is the principle of that act of existing. And although matter receives its act of existing only through some form, yet a form as such does not stand in need of matter in order to exist, because the act of existing is the natural effect of the form itself. However, a form requires matter in order to exist when it is a form of that specific type which does not subsist of itself.¹

Consequently, a form having its act of existing in itself is not prevented in any way from existing apart from matter, and the act of existing is found in a form of this kind. For the very essence of a form is related to its act of existing as a potency is to its proper act. It is in this way, then, that both potency and act are found in forms which subsist of themselves, inasmuch as the act of existing itself is the act of a subsisting form which is not its own act of existing.¹

Moreover, if there is a thing which is its own act of existing, and this is proper to God alone, it does not contain potency and act but is pure act.¹ It is for this reason that Boethius says in his Hebdomads that in the beings which are beneath God in perfection, the act of existing and quiddity are really distinct;² or as some say, that which is and that by which it is differ from each other.³ For the act of existing itself of a thing is that by which a thing exists; just as running is that by which someone runs. Consequently, since the soul is a certain form which subsists of itself, it can be composed of act and potency, that is, of an act of existing and an essence, but not of form and matter.⁴

Seventh, it is asked whether the angel and the soul are of different species.¹

Hence, with this view of Origen shown as false, some adopt a similar position,¹ claiming that all intellectual substances are of the same species for the reasons mentioned in the objections. However, this position is seen to be impossible. For if the angel and the soul are not composed of matter and form, but are forms alone, as was explained in the preceding question,² every difference whereby angels are distinguished from one another, or from the soul as well, must be a formal one;³ unless perhaps it might be maintained that angels, like souls, were also united to bodies in order that there might be a material difference in them resulting from this relationship with bodies, as we explained above is true of souls.⁴ But this view is not commonly held, and even if it were, it would not lend any weight to this position, because it is evident that the bodies⁵ would differ in species from human bodies to which souls are united. Moreover, there must be different specific perfections for bodies that are diverse in species. Therefore, with this position that angels are forms of bodies shown as false, since they are not composed of matter and form, it follows that angels differ from one another, or from the soul, only by reason of a formal difference.⁶ But a formal difference diversifies species, for the form gives a thing its mode of existing.⁷ Hence, it follows that angels not only differ in species from the soul, but also from each other.

However, even if someone claims that angels and souls are composed of matter and form, this position¹ cannot be upheld. For if there were one matter common to angels and souls alike, just as there is one matter for inferior bodies,² diversified only by form, the division of that one common matter would have to be the principle whereby angels are made distinct from one another, and from the soul. Now since it is of the very account of matter in itself to be void of all form, the division of matter could not be understood to exist before it received a form, which is given a multiple existence as a result of the division of matter, unless matter itself were divided by quantitative dimensions.³ Hence the Philosopher says in Physics 1 that substance remains indivisible when quantity is removed.⁴ However, things which are composed of matter determined by dimensions are themselves bodies, not merely things united to a body. According to this argument, therefore, the angel and the soul are bodies. Now no one of sound mind maintained this, particularly because it has been proved that understanding cannot be the act of a body.⁵ Certainly, if the matter of the angels and that of the soul is not one and common, just as it is maintained that there is not one common matter for heavenly and earthly bodies, but belongs to diverse orders, this can only be because it is ordered to different forms, and thus material diversity of this sort causes diversity of species. For this reason, it is clearly impossible for the angels and the soul to be of the same species.

However, the way they differ remains to be investigated. We must acquire our knowledge of intellectual substances by considering material substances. Now in material substances different grades of natural perfection constitute different species.¹ Indeed, this becomes quite obvious if we reflect upon the genera of material substances.² For it is evident that mixed bodies surpass the elements in the order of perfection; plants surpass minerals; animals surpass plants; and in singular genera a diversity of species is found in accordance with the order of natural perfection. For among the elements, earth is lowest, and fire most noble.³ Likewise, in the case of minerals,⁴ nature is found to ascend by degrees through diverse species up to the species of gold. In plants also, nature ascends progressively up to the species of perfect trees; and in animals up to the species of man. Moreover, certain animals are very near to plants, that is, the immobile ones which have touch only. Similarly, certain plants are more like inanimate bodies, as is clear from what the Philosopher says in the book On Plants 1.⁵ For this reason, the Philosopher says in Metaphysics 8 that the species of natural things are like the species of numbers, wherein the addition or subtraction of a unit changes the species.⁶ Consequently, in immaterial substances also a different grade of natural perfection causes difference in species.⁷

But a grade of perfection is in some respect different in the case of immaterial substances from what it is in the case of material substances. For wherever diversity of grades exists, the grades must be considered through their order to some one principle.¹ Therefore, in material substances diverse grades are observed to diversify species in relation to the first principle, matter. For this reason, first species² are most imperfect, whereas species farther removed from matter are more perfect, and related to the first by the addition of higher perfections. For instance, mixed bodies have a more perfect species than the elements have because they possess in themselves the perfections of the elements and higher perfections as well. Hence, the relation of plants to mineral bodies, and that of animals to plants, is similar.

In the case of immaterial substances, the order of diverse grades of species is certainly not considered in relationship to matter, which they do not have, but in relationship to the first agent,¹ who must be most perfect.² Consequently, in the case of immaterial substances, the first species³ is more perfect than the second, inasmuch as the former bears greater likeness to the first agent. The second species has less perfection than the first, and so on successively down to the last of them. Now the entire perfection of the first agent consists in this, that he has in one simple nature all his goodness and perfection. Therefore, the nearer an immaterial substance is to the first agent, the more does it have its perfection and goodness in one simple nature, and the less does it require inhering forms for its perfection.⁴ This continues progressively down to the human soul which occupies the lowest place among immaterial substances, just as prime matter holds the lowest place in the genus of sensible things. Hence, the soul does not have intelligible forms in its very nature, but is in potency to them, just as matter is to sensible forms. Therefore, in order to perform its proper operation, the soul must be actuated by intelligible forms by acquiring them from external realities through its sensory powers. And since the operation of a sense is performed through a bodily organ, it is proper to the soul, according to the very condition of its nature, to be united to the body, and to be part of the human species, not having a complete species in itself.

Eighth, it is asked whether the rational soul should be united to a body such as man possesses.¹

Therefore, if the human soul is capable of being united to a body, because it needs to receive intelligible species from things through the intermediary of the senses, then the body, to which the rational soul is united, must be one which can most adequately present to the intellect those sensible species from which are derived the intelligible species existing in the intellect. Hence, the body to which the rational soul is united must be best disposed for sensory operation.

But although there are several sensory powers, still there is one which is the basis of the others, namely, touch, in which every sensible nature is principally rooted. For this reason, it is also said in On the Soul 2 that an animal derives its name from this sense.¹ This is the reason why, when this sense is unmoved, as occurs during sleep, all other senses are unmoved. Again, not only are all the other senses rendered inactive by an excess of their proper sensible objects—as sight, for instance, is made inoperative by very bright objects, and hearing by too intense sounds—but so also is the sense of touch rendered incapable of performing its proper operation by an excess of its sensible object, for example, excessive warmth or cold. Therefore, since the body to which the rational soul is united must be best disposed for a sensitive nature, it must have the most competent organ of touch. And so, it is said in On the Soul 2 that among all animals we have this sense to a greater degree, and also that one man is more adept than another in intellectual operations as a result of this sense.² For we see that those who have tender flesh, that is, those who are of good touch, are well-endowed mentally.³

Now since the organ of any sense must not possess actually any of the contraries of which a sense is perceptive, but must be in potency to them in order that it may be able to receive them—because the recipient must be deprived of the thing received—the case must be otherwise for the organ of touch than it is for the organs of the other senses. For the organ of sight, that is, the pupil of the eye, is deprived completely of white and of black, and of every kind of color whatever. It is similar in the case of hearing and smell. But this cannot occur in the case of the sense of touch, for touch is capable of experiencing those qualities which the animal body must be composed of, namely, hot and cold, wet and dry. For this reason, it is impossible for the organ of touch to be deprived completely of its sensible objects; rather, it must be reduced to a mean, because in this way it is in potency to contraries. Therefore, since the body to which the rational soul is united must be best disposed for the sense of touch,¹ it must be brought in the fullest measure to an intermediate state by the harmonious combination of its constituent elements and their qualities.

In this way it is evident that the total operation of an inferior nature reaches its highest peak in man as a most perfect being. For we see that the operation of nature ascends progressively from the simple elements, by blending them, until it reaches the most perfect mode of combination, which is the human body.¹ Consequently, this disposition of the human body, to which the rational soul is united, must exist in order that the body may possess the most tempered combination.²

Moreover, if anyone also wishes to examine the particular dispositions of the human body, he will find them ordered to this end, that man may have the best sense. Therefore, man, in proportion to his size, has a larger brain than any other animal, because a good disposition of the brain is necessary for the good condition of the internal sensitive powers, namely, the imagination, the memory, and the cogitative power.¹ And in order that his operation may be freer, he has his head placed on high. For man is the only erect animal; the others, indeed, are bent over.² Furthermore, in order to have this erectness and to preserve it, there must exist in the heart an abundance of heat, by which many spirits are generated, so that the body may be maintained erect by this copious amount of heat and spirits.³ The fact that a man stoops over when he is old is a sign of this, because his natural heat is diminished.⁴ In the light of what is stated above, the account of a disposition of the human body must be determined in relation to the particular dispositions proper to man.

However, we must take into consideration that in those things which are constituted of matter, some dispositions exist in the matter itself, and that on account of these a definite matter is chosen for a definite form. There are also some dispositions which proceed from the necessary character of matter, and not from the choice of the agent; for instance, when an artisan chooses hardness in iron to make a saw in order that it may be useful for sawing. But the fact that sharpness can be given to iron, and that it can rust, results from the necessary character of matter. For the artisan would rather choose a matter in which defects are not present, if it could be found. But because it cannot be found, the artisan does not neglect to work with the available matter of this kind simply because of the defects intrinsic to such matter.¹

This also occurs in the human body, for, likewise, whatever is combined and disposed according to parts in order that such a body may be best fitted for sensitive operations, is selected in this matter by the maker of man. But that this body is corruptible, that it may become fatigued, and have defects of this kind, follows from the necessary character of this matter. For the body, as a mixture of contraries, must be subject to such defects. Nor can any objection be raised in view of the fact that God could make it otherwise, because we do not investigate what God could make in the establishment of nature, but what the nature of things undergoes as made, as Augustine says in On the Literal Interpretation of Genesis.¹

Moreover, it must be recognized that when God remedied these defects in man at his creation, he employed the help of original justice¹ whereby the body was made subject completely to the soul and the soul to God, so that neither death nor passion nor any defect could affect man unless the soul were first separated from God.² But when the soul turned away from God through sin, man was deprived of this gift, and is subject to the defects which are intrinsic to the nature of matter.

Ninth, it is asked whether the soul is united to corporeal matter through a medium. ¹

From this it is obvious that an intermediary substantial form cannot intervene between a substantial form and matter, as some wished to maintain. For these men held that there exists in matter an order of diverse forms, one of which is arranged under another in accordance with the order of genera; as if one were to say, for instance, that matter is given the act of existing of a substance through one form; the act of existing of a body through another; the act of existing of a living body through still another; and so on. But if this position is adopted, only the first form which gives a thing its act of existing as a substance would be a substantial one. The other forms, indeed, would all be accidental ones, because it is a thing’s substantial form that makes it be a substance, as we have already shown.¹ Therefore, it is necessary to say that a thing has substantiality, exists in the ultimate species,² under which there are no other species, and in all intermediate genera, through one and the same form.

Now the forms of natural things are like numbers whose species change when a unit is added or subtracted, as is pointed out in Metaphysics 8.¹ It follows, therefore, that the diversity of natural forms, in accordance with which matter is constituted in diverse species, is to be understood as resulting from this fact, that one adds a perfection over and above another.² For example, one form gives matter corporeal existence only. This must be below the grade of animal forms, because matter is in potency only to corporeal forms. For those things which are incorporeal are immaterial, as was shown in the preceding question.³ A second, more perfect, form gives matter vital existence in addition to corporeal existence. Another, still higher, form confers on it sensory existence in addition to vital and corporeal existence; and so on successively.

Therefore, a more perfect form, constituting with matter a composite being in the perfection of an inferior grade, must be considered as matter with respect to a higher perfection; and so on up the scale.¹ For instance, prime matter, so far as it now exists in a corporeal mode, is matter with respect to the higher perfection of life. And so, body is the genus of living body, and animated or living is the specific difference. For genus is derived from matter, and difference from form.² Thus, in a certain way, one and the same form actualizing matter in a lower grade of perfection is midway between matter and that same form actualizing matter in a superior grade.

But matter, so far as it is understood to have substantial existence as a perfection of an inferior grade, can, therefore, be regarded as the subject of accidents. For a substance in that inferior grade of perfection must have a proper accident which necessarily inheres in it. Likewise, from the fact that matter has corporeal existence through forms, it immediately follows that there are dimensions in matter whereby it is understood to be divisible into different parts, so that it can receive different forms corresponding to its different parts.¹ Furthermore, from the fact that matter is known to have a certain substantial mode of existing, matter can be understood to receive accidents by which it is disposed to a higher perfection, so far as it is fittingly disposed to receive that higher perfection. Moreover, dispositions of this kind are understood to exist in matter prior to the form, inasmuch as they are given existence in matter by an agent, although there are some improper accidents of the form that are caused in the matter only by the form itself. Hence, such accidents are not understood to exist as dispositions in matter prior to the form; rather, the form is understood to be prior to the proper accidents as a cause is to its effects.

Consequently, since the soul is a substantial form, because it places man in a determinate species of substance, no other substantial form intervenes between the soul and prime matter. But man is perfected in different grades of perfection by the rational soul itself, so that he is a body, a living body, and a rational animal.¹ However, matter—being understood to receive, from the rational soul itself, perfections of an inferior grade, for instance, that of being a body, a living body, and an animal—must also be understood to have, at the same time, appropriate dispositions so that it may be matter befitting a human soul, inasmuch as the soul gives the body its ultimate perfection. So, therefore, the soul, inasmuch as it is the form which gives the act of existing absolutely, does not have any intermediary between itself and prime matter.

But because the same form which gives matter its act of existing is also a principle of operation, for a thing acts so far as it is in act,¹ then the soul, like any other form, must be a principle of operation.² But it must be considered that a gradation of forms in the order of operation corresponds to the gradation of forms in the order of existence, for an operation is an act of an agent in act. Therefore, the greater perfection a form possesses with respect to conferring the act of existing, so much the greater is its power of operating. Hence, more perfect forms have a greater number of operations and more diverse ones than less perfect forms. And so it is that a diversity of accidents suffices for a diversity of operations in the case of less perfect things. But in the case of more perfect things, a diversity of parts is required as well, and the greater the diversity of parts, the more perfect the form will be. For we see that diverse operations are proper to fire because its accidents differ, for example, to rise upward in virtue of its lightness, to heat in virtue of its heat, and so on.³ However, any one of these operations belongs to any part of fire. But in animate bodies which have nobler forms, different operations are allotted to different parts; for instance, in plants there is one operation performed by the roots, another by the trunk, and still another by the branches. And the more perfect living bodies are, so much the more diverse must their parts be in view of their greater perfection.⁴ Therefore, since the rational soul is the most perfect of natural forms, there is found in man the greatest diversity of parts because of his different operations. Furthermore, the one soul performing these operations confers substantial existence in a manner befitting the operations of the parts themselves. An indication of this fact is that, when the soul ceases to animate the body, neither flesh nor eye remains except in an equivocal sense.⁵

But since there must be an order of instruments in keeping with the order of operations, and since there is a natural precedence among the different operations which flow from the soul, one part of the body must be moved to perform its operations by another part. Thus, a medium intervenes between the whole body and the soul as the mover and principle of its operations. For after a certain primary mediating part of the body has been moved, that part moves the other parts to perform their operations.¹ So it is that the soul, by means of the heart, moves the other members of the body to perform their vital operations.² But since the soul gives to the body its act of existing, it immediately gives to all parts of the body their substantial and specific mode of existing. And this is what many assert, namely, that as a form the soul is united to the body without an intermediary, but that as a mover it is united to the body through an intermediary.³

Moreover, this view is in keeping with the position of Aristotle, who maintains that the soul is the substantial form of the body.¹ However, some who, following Plato’s theory, hold that the soul is united to the body as one substance is to another, had to posit means through which the soul is united to the body.² For diverse and disparate substances are unified only if something exists to unite them. For this reason, some held that there is a certain spirit and humor existing as a medium between soul and body,³ other posited light,⁴ still others, the powers of the soul, or something else of this sort. But none of these are necessary if the soul is the form of the body, because anything whatever, inasmuch as it is a being, is one.⁵ Hence, a form is united to prime matter by virtue of itself and not by any other bond, because a form, by its very nature, gives to matter its act of existing.⁶

Now whatever belongs to the intellective part moves the body only by means of that which belongs to the sensitive part. For when a movement has to do with some particular thing, the universal apprehension that belongs to the intellect causes movement only by means of something particular belonging to sense. Hence, when we divide a man or an animal into a part that causes movement and one that is moved, we do not divide them into a soul and a body exclusively, but into a soul and an animated body. For that part of the animated body whose operation it is to apprehend and to desire, moves the whole body. But if it be supposed that the intellective part moves the body directly, so that the part causing movement in man is the soul alone, then the answer will be in accordance with the preceding explanation.¹ For the human soul will be a mover in virtue of what is supreme in itself, namely, its intellective part. Moreover, the moved part will not be prime matter alone, but prime matter inasmuch as it is given a corporeal and vital act of existing. Nor will it be moved by any other form than the soul. Hence, it will not be necessary to maintain that a substantial form acts as an intermediary between the soul and prime matter.

However, there is a certain movement in the animal that is not the result of apprehension and desire—that is, the movement of the heart, the movement also of growth and decay, and the movement of nutrition which is diffused throughout the whole body, and which the animal has in common with plants. Now with respect to this kind of movement, we must maintain that, as inferior forms are the principles of movement in natural bodies, so also is the soul the principle of movement in animal bodies. For the animal soul not only bestows what is proper to its nature as such but also gives those perfections which belong to a lower order of forms, as is evident from what has been said.

Hence, the Philosopher says in On the Soul 2 that the soul is the nature of this specific type of body.¹ For this reason, the operations of the soul are divided into animal operations and natural operations. That is to say, those operations which proceed from the soul in keeping with its proper nature are called animal operations, whereas those which come from the soul inasmuch as it produces the effect of inferior natural forms are called natural operations.

According to this, therefore, it must be said that, as fire through its natural form has a natural movement whereby it tends upwards, so also any part of an animated body, in which there is found movement not resulting from apprehension, has this movement naturally through its soul. For as fire tends upward by nature, so also the blood is moved naturally to its proper and determinate place. Similarly, the heart is moved naturally by its proper movement, although the dissolution of spirits, made from the blood, by which the heart is expanded and contracted, cooperates in this activity, as Aristotle points out in the place where he treats of exhalation and inhalation.¹ Consequently, the first part of the body in which such movement is found is not a self-mover, but is moved naturally, just as fire is. However, this part moves another part, and thus the whole animal is a self-mover, because one part of it is a mover, and another is moved.²

Tenth, it is asked whether the soul exists in the whole body and in each of its parts.¹

Moreover, it is impossible for a thing to receive its act of existing and species (as it does from a form) from a principle existing in separation from it, because this would be similar to the position of the Platonists, who maintained that such sensible things receive their act of existing and species by participating in forms which exist apart from things themselves.¹ But a form must be an intrinsic principle of the thing whose act of existing it is responsible for, because form and matter are the intrinsic principles constituting the essence of a corporeal thing.²

Hence, according to the teaching of Aristotle, if the soul as a form gives to each part of the body its act of existing and species, it must be present as a form in each part of the body.¹ And for this reason, the soul is said to exist in the whole body because it is the form of the whole.

Therefore, if it is the form of each part of the body, it must exist in each part and not in the whole alone, nor in one part alone. Moreover, this definition of the soul is an appropriate one,¹ for the soul is the act of an organic body. However, an organic body is composed of different organs. Hence, if the soul as a form existed in one part of the body only, it would not be the act of an organic body, but that of one organ alone, for instance, the heart or some other part, and the remaining parts would be perfected by different forms. And thus, the whole would not be one thing by nature but merely by composition. Hence, it follows that the soul exists in the whole body and in each of its parts.

But since it is also asked whether the whole soul exists in the whole body and in each of its parts, we must consider how this is to be explained. For totality can be attributed to a form in a threefold manner, according to the three ways in which it is proper for a thing to have parts.¹ For a thing has parts, in one way, resulting from quantitative division, that is, according as a number or a magnitude is divided. However, totality of number or that of magnitude does not apply to a form, except perhaps in an accidental way, for instance, in the case of forms which are divided accidentally by the division of a continuum, as whiteness is divided as a result of dividing a surface. A thing is said to be a totality in another way in relation to the essential parts of its species, as matter and form are said to be parts of a composite, and genus and difference, in a certain respect, parts of a species. This kind of totality is also attributed to simple essences by reason of their perfection, in this way, that as composites have a perfect species from the union of their essential principles, so also do substances and simple forms which have a perfect species in virtue of themselves. A thing is said to be a totality in a third way in relation to its active and passive powers, inasmuch as these are considered to be parts of it which are distinguished from one another because their operations differ.

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

Now if we suppose, for the present, that there is only one soul in the human body—we will explain this later¹—we must maintain that it is not divided by dividing that species of quantity which is numerical in nature. It is also obvious that the soul is not divided by dividing a continuum. This is particularly true of the souls of perfect animals which do not live when dissected. However, it would perhaps be different in the case of the souls of ring-worms, in which there is one soul actually and many potentially, as the Philosopher teaches.² Therefore, in the case of the soul of man and that of any perfect animal, it follows that totality can be considered only so far as the soul’s species and its passive or active power are concerned.

Hence, we say that the soul by its very essence is the form of the body, and that it exists as such in each part of the body, as has been shown,¹ because the perfection of the species comes from the soul in virtue of its very essence. Consequently, the whole soul exists in each part of the body according to the whole of its specific perfection.

However, if totality is taken so far as the soul’s active and passive powers are concerned, then the whole soul does not exist in each part of the body. Nor, if we speak of the soul of man, does the whole soul, according to the totality of its powers, exist in the whole body. For it was shown in the preceding articles¹ that the human soul possesses the power of performing certain operations without communicating in any way with the body, that is, the acts of understanding and willing, as it exceeds the capacity of the body. Hence, the intellect and the will are not the acts of any bodily organ.

However, with respect to those operations which the soul exercises through bodily organs, the soul’s active and passive powers as a whole exist in the whole body, although not in each part of the body, because different parts of the body are proportioned to different operations of the soul.¹ Consequently, with respect to any one power, the soul exists only in that part of the body which takes care of the operations exercised by that particular part.

Eleventh, it is asked whether the rational, sensitive, and vegetative souls in man are substantially one and the same.¹

However, according to this position, neither a man nor an animal would have its unity absolutely and in virtue of its very nature,¹ because a being that has unity absolutely and in its own right does not result from the conjunction of a mover and something movable. Nor, on Plato’s hypothesis, would generation and corruption strictly speaking exist when a body receives a soul or loses it. Consequently, it must be said that the soul is united to the body not only as a mover but as a form. This is also evident from the preceding arguments.²

But even if this position is adopted, it still follows from Plato’s principles that there are several souls in man and in the animal. For the Platonists maintained that universals are separate forms which are predicated of sensible things inasmuch as sensible things participate in them.¹ For example, Socrates is called an animal inasmuch as he participates in the idea “animal,” and a man inasmuch as he participates in the idea “man.” The consequence of this is that there is one form essentially in virtue of which Socrates is said to be an animal, and another in virtue of which he is said to be a man. Hence, it follows in turn that the sensitive and rational souls differ substantially.

But this cannot be maintained, for a being having unity in its own right cannot be constituted of diverse things having actual existence, because if terms are predicated of some subject by reason of diverse forms having existence of themselves, one is predicated of another accidentally.¹ For instance, it is said of Socrates that he is white according to whiteness, and musical according to music. Therefore, musical is predicated of white accidentally.² Hence, if Socrates is said to be a man and an animal according to different forms, it would follow that this predication, “man is an animal,” is an accidental one, and that man is not really what an animal is.

However, it happens that an essential predication is made through different forms when they are intrinsically related to one another, as when it is said that a thing having surface is colored.¹ For color exists in a substance through the medium of its surface. But this mode of essential predication occurs, not because the thing predicated is placed in the definition of the subject, but rather the reverse. For surface is placed in the definition of color just as number is placed in the definition of the equal. Therefore, if animal were predicated of man through this mode of essential predication, when the sensitive soul is related as matter to the rational soul, assuming they are diverse, it would follow that animal is not predicated essentially of man but rather the reverse.²

An additional difficulty follows. For a being having unity absolutely cannot be constituted of diverse things having actual existence unless there is something uniting them and binding them to one another in some manner.¹ Therefore, if Socrates were an animal and rational according to different forms, these two forms would need a unitary principle to make them substantially one. Therefore, since, on Plato’s hypothesis, no such unitary principle is to be found, it will follow that the unity of a man will be a unity of aggregation alone, like that of a heap of things which is relatively one and absolutely many. So neither will man be a being absolutely, because, so far as a thing is a being, to that extent it is one.²

Still, another incongruity follows. For the form in accordance with which an individual substance receives a generic predication must be a substantial one because a genus is a substantial predicate. And thus, the sensitive soul, in virtue of which Socrates is said to be an animal, must be his substantial form, and so must give to the body its act of existing in the absolute sense, and make it to be this particular thing. Therefore, if the rational soul differs substantially from the sensitive, it does not make the body to be this particular thing, nor does it give to the body an act of existing in the absolute sense, but only relatively. For in that case a rational form will accrue to a thing already actually subsisting. Consequently, it will not be a substantial form but an accidental one, and thus it will not give Socrates his species, for a species is also a substantial predicate.¹

It follows, therefore, that a man’s soul, which is rational, sensitive, and vegetative, is substantially one only. This is a consequence of the argument given in a preceding article¹ concerning the order of substantial forms, namely, that no substantial form is united to matter through the medium of another, but that a more perfect form gives to matter whatever an inferior form does, and something over and above. Hence, the rational soul gives to the human body everything that the sensitive soul gives to the brute and the vegetative soul gives to the plant, and something over and above.² For this reason, the soul in man is both vegetative and sensitive and rational. The following example also attests to this, namely, that when the operation of one power is intense, that of another is impeded;³ and contrariwise, there is an overflowing of one power into another, which would occur only if all the powers were rooted in one and the same essence of the soul.⁴

Therefore, our explanation must be different, namely, that the generation of an animal is not one simple generation alone, but that many generations and corruptions follow one another.¹ For it is said that first the animal has the form of semen, then the form of blood, and so on successively until generation is completed. And, therefore, since corruption and generation do not take place without the loss of one form and the acquisition of another, the imperfect form which first exists within the embryo must be discarded and a more perfect one assumed.² This continues until the thing conceived has acquired its perfect form. Consequently, it is said that the vegetative soul first exists in the semen, but that it is lost in the process of generation, and that another soul succeeds it which is not only vegetative, but also sensitive. Then another soul is added to this which is at once vegetative, sensitive, and rational.

Twelfth, it is asked whether the soul is its powers.¹

Now this opinion cannot be maintained. First, indeed, because anything whatever that acts, acts according as it is in act.¹ For fire heats not inasmuch as it is actually bright, but inasmuch as it is actually hot. It is for this reason that every agent produces an effect similar to itself.² Wherefore, the principle by which an agent acts must be known from its effects, for both must conform. Hence, it is said in Physics 2 that the form and the thing generating are the same in species.³ Therefore, when an effect does not result from the substantial mode of existing of the one acting, it is impossible that the principle by which such an effect is brought about belongs in any way to the essence itself of the thing acting. This is quite evident in natural agents. For since a natural agent in generating acts by changing matter with respect to some form—which change occurs inasmuch as matter is first disposed to receive the form, and then acquires it according as generation is the terminus of alteration⁴—the principle which acts immediately on the side of the agent must be an accidental form corresponding to the disposition of the matter. Now an accidental form must act in virtue of a substantial form, and as an instrument of the latter, otherwise it would not induce a substantial form by its activity. For this reason, no principles of action appear in the elements except their active and passive qualities, which still act in virtue of their substantial forms, and on account of this their action is terminated not only in accidental dispositions, but in substantial forms as well.⁵ For in things made by art, the action of an instrument is terminated in the form intended by the artisan. Indeed, if there is an agent that produces a substance directly and immediately by its action—just as we speak of God who produces the substances of things by creating them, and as Avicenna speaks of the agent intellect, which, by virtue of its own power, infuses substantial forms into these inferior things—then an agent of this sort acts through its own essence, and thus its active power will not differ from its own essence.⁶

Concerning passive power, it is clear that a passive power which is ordered to a substantial act belongs to the genus of substance, whereas one that is ordered to an accidental act belongs to the genus of accident by reduction as a principle and not as a complete species, because every genus is divided by potency and act. Accordingly, a potential man belongs to the genus of substance, and potentially white belongs to the genus of quality.

Now it is evident that the powers of the soul, whether active or passive, are not spoken of directly with respect to something substantial, but with respect to something accidental. Similarly, to be understanding or sensing actually is not a substantial mode of existing, but an accidental one to which the intellect and sense are directed. It is similar with respect to being large or small, to which the augmentative power is ordered. Indeed, the generative and nutritive powers are directed to the production or conservation of a substance, but by changing matter.¹ Wherefore, an action of this kind, like that of other natural agents, is performed by a substance through the medium of an accidental principle. Hence, it is evident that the essence of the soul is not the immediate principle of its operations, but that it operates through accidental principles. Consequently, the powers of the soul are not the essence itself of the soul but are properties of it.

This is also evident from the very diversity of the soul’s actions, which differ in genus and cannot be attributed to one immediate principle, because some are actions and some are passions, and are distinguished by other differences of this sort which must be attributed to different principles. Consequently, since the essence of the soul is one principle, it cannot be the immediate principle of all its actions, but must have many different powers corresponding to its different actions, for a power is said to be reciprocally related to its act.¹ Hence, there must be a diversity of powers in accordance with the diversity of operations. For this reason, the Philosopher says in Ethics 6 that the scientific power of the soul, which is concerned with necessary things, and the ratiocinative power, which is concerned with contingent things, are different powers because the necessary and the contingent differ in genus.²

Now no accident of any kind ever constitutes part of the essence of a thing, and thus an accident is never found in a thing’s definition. Hence, we understand the essence of a thing without thinking of any of its accidents. However, the species cannot be understood without the accidents which result from the principles of the species,¹ although the species can be understood without the accidents of the individual, even the inseparable accidents. Indeed, there can be not only a species but also an individual without the separable accidents. Now the powers of the soul are accidents in the sense of properties. Therefore, although the essence of the soul is understood without them, still the existence of the soul is neither possible nor intelligible without them.

Thirteenth, it is asked about the distinction between the powers of the soul, that is, whether the powers of the soul are distinguished from one another by their objects.¹

Now it is necessary to consider the difference among objects inasmuch as they are objects of the soul’s activities, and not according to some other way.¹ For a species is differentiated in any genus only by the specific differences which essentially divide the genus. The species of “animal,” for instance, are not distinguished by white and by black, but by rational and non-rational.

Furthermore, it is necessary to consider three grades in the actions of a soul. For the action of a soul transcends that of the nature operating in inanimate things. But this occurs in two ways. First, with respect to the manner of acting; second, with respect to what is produced by the action.¹ Now with respect to the manner of acting, every action of a soul must transcend the operation or action of an inanimate nature. For every operation of a soul must proceed from some intrinsic agent, because an action of a soul is a vital action, and moreover, every living thing is one that moves itself to operation.² However, so far as the effect produced is concerned, not every action of a soul transcends an action of the nature of an inanimate thing. For the effect produced, that is, a natural mode of existing, and the things necessary for it, must be present in the case of inanimate bodies just as they are in the case of animate ones. But in the case of inanimate bodies, the effect is brought about by an extrinsic agent, whereas in the case of animate bodies, it is caused by an intrinsic agent.³ The actions to which the powers of a vegetative soul are directed are of this sort.⁴ For the generative power is directed to giving existence to the individual thing; the augmentative power, to giving the thing its proper size; and the nutritive power, to preserving the thing in existence.⁵ But in inanimate things these effects are brought about only by an extrinsic agent. For this reason, the aforementioned powers of a soul are said to be natural.

However, there are other higher actions of a soul which transcend the actions of natural forms, and also the effects produced by them, seeing that all things are disposed by nature to exist in the soul with an immaterial existence. For the human soul, in a certain respect, is all things by sensing and understanding.¹ Moreover, there must be different grades of such immaterial existence.

For there is one grade inasmuch as things exist in the soul without their proper matter, but with the singularity and individuating conditions which are the result of matter. This is the grade of sense, which is receptive of individual species without matter, yet receives them in a bodily organ.¹

Now the intellect which receives species completely abstracted from matter and material conditions, and without a bodily organ, constitutes a higher and more perfect grade of immateriality.¹

Furthermore, just as a thing has a natural inclination toward something, and has movement and action in order to pursue that toward which it is inclined through its natural form, so also does the inclination toward a thing apprehended by sense or by intellect follow upon the apprehension of a sensible or intelligible form.¹ This inclination belongs to the appetitive power.² And again, as a consequence of this, there must be some movement by which it attains the thing desired. This pertains to the motive power.

Moreover, five things are required for the perfect sense knowledge which an animal should have.

First, that sense receive species from sensible things and this pertains to the proper sense.

Second, that the animal make some judgment about the sensible qualities received and distinguish them one from another, and this must be done by a power to which all sensible qualities are related.¹ This power is called the common sense.

Third, that the species of sensible things which have been received be retained. Now an animal needs to apprehend sensible things not only when they are present, but also after they have disappeared. And it is necessary that this also be attributed to some power. For in corporeal things there is one principle that receives, and another that retains, because things which are good recipients are sometimes poor retainers.¹ This power is called imagination or “fantasy.”²

In the fourth place, the animal must know certain intentions which sense does not apprehend, such as the harmful, the useful, and so on. Man, indeed, acquires a knowledge of these by investigation and by inference, but other animals, by a certain natural instinct.¹ For example, the sheep flees naturally from the wolf as something harmful. Hence, in animals other than man a natural estimative power is directed to this end, but in man there is a cogitative power which collates particular intentions.² This is why it is called both particular reason and passive intellect.³

In the fifth place, it is necessary that those things which were first apprehended by sense and conserved interiorly be recalled again to actual consideration. This belongs to a memorative power, which operates without any investigation in the case of some animals, but with investigation and study in the case of men. Therefore, in men there is not only memory but also reminiscence.¹ Moreover, it was necessary that a power distinct from the others be directed to this end, because the activity of the other sensitive powers entails a movement from things to the soul, whereas the activity of the memorative power entails an opposite movement from the soul to things. But diverse movements require diverse motive principles, and motive principles are called powers.

Now because the proper sense, which is first in the order of sensitive powers, is changed immediately by sensible objects, it was necessary for it to be divided into different powers in accordance with the diversity of sensible modifications.¹ For the grade and order of modifications by which the senses are altered by sensible qualities must be considered in relation to immaterial modifications, because sense is receptive of sensible species without matter.

Hence, there are some sensible objects whose species, although they are received immaterially in the senses, still cause a material modification in sensitive animals. Now qualities which are also principles of change in material things are of this sort, for instance, hot and cold, wet and dry, and the like.¹ Hence, because sensible qualities of this kind also modify us by acting upon us,² and because material modification is made by contact, it was necessary that such sensible qualities be sensed by making contact with them.³ This is the reason why the sensory power experiencing such qualities is called touch.

However, there are some sensible qualities which do not, indeed, change us materially, although their mutation has a material change connected with it. This occurs in two ways.

First, in the way that the material change affects the sensible quality as well as the one sensing. This pertains to taste.¹ For, although the taste of a thing does not change the sense organ by making it the tasted thing itself, nevertheless this modification does not occur without some change taking place in the thing tasted as well as in the organ of taste, and particularly as a result of moisture.

Second, in the way that the material change affects the sensible quality alone. Now change of this sort is caused either by a dissipation and alteration of the sensible object, as occurs, for instance, in the sense of smell,¹ or by a local change only,² as occurs in the case of hearing.³ So it is that hearing and smell sense not by contact with an object, but through an extrinsic medium, because they occur without a material change on the side of the one sensing, although material change does take place in the sensible object. However, taste alone senses by contact because it requires a material modification in the one sensing.⁴

Furthermore, there are other sensible things which modify a sense without a material change being involved, such as light and color, and the sense which apprehends these is sight. Hence, sight is the noblest of all the senses and extends to more objects than the other senses do, because the sensible qualities perceived by it are common both to corruptible and incorruptible bodies.¹

Similarly, the appetitive power,¹ which follows the apprehension of the senses, must be divided in two ways.² For a thing is appetible either because it is delightful and suitable to the senses, and the concupiscible power is directed to this;³ or because the capacity of enjoying things delightful to the senses is made possible through it, which sometimes occurs together with something that is displeasing to sense—for instance, when an animal by fighting makes possible the enjoyment of something properly delightful by driving away anything that hinders this. The irascible power is directed to this end.⁴

Moreover, since the motive power is directed to local movement, it is diversified only with respect to different local movements.¹ These movements may differ for different animals, since some of them are able to crawl, some to fly, some to walk, and some to move in other ways; or they may differ for different parts of one and the same animal because the particular parts of the body have their own movements.

Again, the grades of intellectual powers are similarly distinguished into cognitive and appetitive.¹ Moreover, movement is common to sense and to the intellect, for the same body is moved by each of these powers through one and the same movement. Again, intellectual cognition requires two powers, namely, the agent intellect and the potential intellect, as is clear from the previous articles.²

Consequently, it is obvious that there are three grades of powers in the soul, namely, the vegetative, sensitive, and rational. Moreover, there are five genera of powers, that is, the nutritive, sensitive, intellective, appetitive, and locomotive, and each of these contains many powers under itself, as has been pointed out.¹

Fourteenth, it is asked about the incorruptibility of the human soul.¹

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.¹ For, as the Philosopher proves in On the Soul 3, understanding is not an act executed by any bodily organ.² 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.³ Now every bodily organ possesses a sensible nature. But the intellect, by which we understand, is capable of apprehending all sensible natures.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.⁵ 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.⁶

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.¹ 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.² Now it was shown in preceding articles³ 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.¹ 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.² Still others held that the intellect, by which man understands, is a separate substance.³ But the falsity of all these opinions has been demonstrated in preceding articles.⁴ 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.¹

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.¹ 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.

Fifteenth, it is asked whether the soul, when separated from the body, is capable of understanding.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.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.² Therefore, the act of understanding does not remain in the soul when it exists in separation 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.

c. Furthermore, understanding is either a form of imagination or is impossible without imagination, as the Philosopher says in On the Soul 1.¹ 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.

For some men, namely, the Platonists,¹ 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.²

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.¹ 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.² 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.¹

Now if this theory be adopted, the whole problem with which we are dealing becomes simple and easy.¹ 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.² 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.¹ For this union is not for the sake of the soul,² 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.³ 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.¹ 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.¹

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.¹ 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.² 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.³

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.¹

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.¹ For we cannot even reflect upon the things we know without turning to phantasms, although Avicenna himself is of a contrary opinion.² 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.³

It is evident also that we have need of certain phantasms in things divinely revealed to us through the influence of superior substances.¹ 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.² 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.¹ Now just as colors are made actually visible by light, so phantasms are made actually intelligible only by the agent intellect.² 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.³ 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.¹ 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,¹ 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.² 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,¹ 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.¹

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.¹ 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.²

It is undoubtedly true, however, that bodily movements and the activity of the senses prevent the soul from receiving infused knowledge from separate substances.¹ It is for this reason that certain things are revealed to persons during sleep, and to those who have momentarily lost their senses.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.³ 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.⁴ 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.⁵

Sixteenth, it is asked whether the soul, when united to the body, can understand separate substances.¹

For some have maintained that our soul, even when united to the body, is capable of knowing separate substances, and that man’s ultimate happiness actually consists in knowing such substances.¹ However, these theorists entertain different opinions as to the way in which we understand such substances.

For some have maintained that our soul cannot acquire an understanding of separate substances in the way in which we acquire an understanding of those other intelligible objects which we learn about in the speculative sciences. The latter type of knowledge is acquired through definitions and demonstrations, whereas a knowledge of separate substances, these theorists maintained, can be acquired only as a result of the agent intellect itself being united to us.¹ For they supposed that the agent intellect was a separate substance which by its own nature understands separate substances.² Hence, when this agent intellect shall be united to us, enabling us thereby to understand through itself, as we now understand through intellectual habits of scientific knowledge, we shall, consequently, apprehend separate substances.

Moreover, they explain the manner in which this agent intellect can be united to us so that we may understand. For it is evident from what the Philosopher says in On the Soul 2, that whenever we are said to be so-and-so or to do so-and-so, two things are involved, one having the role of form, the other the role of matter; just as we are said to be made healthy by health and with respect to the body, so that health is related to the body as a form to matter.¹ It is clear also, they say, that we understand by the agent intellect and through intelligible objects-known; for we arrive at a knowledge of conclusions through principles known naturally and through the agent intellect.² Therefore, the agent intellect must be related to intelligible objects-known as a principal agent is to an instrument, and as a form is to matter, or as act is to potency.³ For of two things, the more perfect always has the character of an act with respect to the other.

Moreover, whatever receives in itself that which has the character of a form also receives that which has the character of matter, just as a body having a surface is also receptive of color, which is a kind of form possessed by that surface. Likewise, the pupil of the eye which receives color also receives light, which is the act of color, for by light color is made actually visible.¹

Consequently, in the same way, so far as the potential intellect receives intelligible objects-known, to that extent does it receive from the agent intellect. Hence, when the potential intellect receives all objects-known, then at that time it will receive the agent intellect unto itself completely, and thus the agent intellect will assume the character of a form in the potential intellect, and it consequently will become one with us.¹

Hence, as we at present understand through the potential intellect, so shall we then understand through the agent intellect, and we shall understand not only all natural things but separate substances as well.

On this point, however, there are differences of opinion among those who subscribe to the theory stated above. For some, holding that the potential intellect is corruptible, assert that the potential intellect is in no way able to know either the agent intellect or the separate substances; but that as long as we remain in a state of union with the agent intellect, we shall know the agent intellect and other separate substances as well through the agent intellect itself, inasmuch as it will be united to us as a form.¹ But others, holding that the potential intellect is incorruptible, assert that the potential intellect is able to know the agent intellect as well as other separate substances.²

Now it is impossible to maintain this position. It is gratuitous and contrary to the meaning of Aristotle’s doctrine. It is impossible to maintain this position because it premises two contradictory affirmations, namely, that the agent intellect is a separate substance existing apart from us, and that we understand through the agent intellect as through a form. Now so far as we carry out an operation by means of something having the character of a form, to that extent do we cause something to exist actually, just as a hot thing heats by its heat inasmuch as it is actually hot. For a thing acts only so far as it is in act.¹ Hence, that by which a thing acts or operates formally must be united to that thing with respect to its very act of existing.² Hence, in the case of two substances existing in separation from one another, it is impossible for one of them to operate formally through the other. Thus, if the agent intellect is a separate substance existing apart from us, we cannot understand by it formally, although we may be able to understand by it actively, as we are said to see by the light of the sun.

The aforesaid position is likewise gratuitous because the arguments advanced for it are not conclusive with necessity. Two considerations make this point clear.

The first, indeed, is because if, as the advocates of this view maintain, the agent intellect is a separate substance, then this intellect will not be related to intelligible objects-known as light is to colors, but as the sun shining is to colors.¹ Hence, simply because the potential intellect receives intelligible objects-known, that intellect is not thereby brought into substantial union with the agent intellect, but is united only to an effect of it, just as the eye by receiving colors is not united to the substance of the sun, but only to the sun’s light.²

The second is because—supposing we grant that the potential intellect, being receptive of intelligible objects-known, is in some way united substantially to the agent intellect—even though the potential intellect receives all intelligible objects-known, the latter being abstracted from phantasms and known demonstratively through the principles of demonstration, it would not follow that the potential intellect had thus been perfectly united with the agent intellect. This could be the case only if it were proved that all those intelligible objects together were equivalent in power and in substance to the power and substance of the agent intellect itself.¹ This is obviously untrue, for if the agent intellect is a separate substance, it is by that fact alone of a higher order of being than all those objects in the natural order which are rendered intelligible by it.

It is also remarkable that these people did not see the evident error in their reasoning. For, although they maintained that all intelligible objects-known were united by one or two of these objects, still it does not follow for this reason, according to them, that we shall know all the other intelligible objects-known. Now it is evident that separate intelligible substances surpass all those objects which they call intelligible objects-known to a far greater degree than all of the latter taken together exceed one or two or any number of themselves. For these objects are all of one genus and have the same mode of intelligibility, whereas separate substances are of a higher order, and have a higher mode of intelligibility.¹ Hence, if the agent intellect is brought into union with us as a form and as the agent of those intelligibles, it does not for this reason follow that it is united to us as a knower of separate substances.

It is likewise clear that this whole position is contrary to the intention of Aristotle, who says in Ethics 1 that happiness is a common good which all who are not deprived of virtue may possess.¹ But to understand all those things which these theorists call intelligible objects-known is impossible for any man,² or at least so rare that in this life no man ever did in fact attain such understanding, except Christ himself, who was both God and man.³ Hence, it is impossible that such knowledge should be required for human happiness. Now the ultimate happiness of man consists in knowing the noblest intelligible objects, as the Philosopher says in Ethics 10.⁴ Thus, it is not necessary for a man to know all intelligible objects-known in order to know those substances which are the noblest intelligibles, and in the knowledge of which human happiness consists.

In another way this whole position is evidently contrary to the meaning of Aristotle’s doctrine. For it is said in Ethics 1 that happiness consists in acting in accordance with perfect virtue.¹ So in order to show clearly and precisely what happiness actually consists in, Aristotle found it necessary, as he says near the end of Ethics 1, to determine the nature of all the virtues.² He maintains that some of these are moral virtues, such as fortitude, temperance, and the like; however, others are intellectual virtues, which he held to be five in number: wisdom, understanding, science, prudence, and art. He says that the chief of these is wisdom, and that ultimate happiness consists in the exercise of wisdom, as appears in his text.³ Moreover, it is clear from the beginning of Metaphysics that wisdom is first philosophy itself.⁴ Hence, it follows, according to Aristotle, that the ultimate human happiness which can be had in this life consists in such knowledge of separate substances as can be acquired through the principles of philosophy, and not through any union with an agent intellect, such as some have vainly imagined.

Wherefore, there is another theory according to which the human soul can attain to an understanding of separate substances through the principles of philosophy.¹ The upholders of this theory proceeded to demonstrate their position as follows. It is evident that the human soul can abstract quiddities from material things and can apprehend them; for this is precisely what happens whenever we grasp what a material thing is. Now if that abstracted quiddity is not a pure quiddity but is itself a thing having a quiddity, then even so the intellect must eventually succeed in grasping the simple quiddity itself alone because it is impossible to go on to infinity in the process of abstraction. And by contemplating simple quiddities, our intellect is, in fact, understanding separate substances because the latter are themselves nothing else than simple quiddities.

However, this argument is entirely inadequate: first of all because the quiddities of material things are of a different order from separate quiddities and have a different mode of existing; so it does not follow that our intellect understands separate quiddities simply because it grasps the quiddities of material things.¹ In the second place, the diverse quiddities apprehended by the intellect themselves differ in species, so that a person who apprehends the quiddity of one material thing does not thereby apprehend the quiddity of another; for example, to understand what is a “stone” is not to understand what “animal” is. Thus, even if we granted that separate quiddities are of the same account as material quiddities, it would follow that one who understands the latter likewise understands the former, unless one happened to subscribe to Plato’s view that separate substances are the species of these sensible things.²

Consequently, in opposition to this doctrine, we must maintain that the intellectual soul of man, by being united to the body, has its vision turned toward phantasms, and is informed in its understanding only through species acquired from phantasms.¹ This agrees with the statement of Dionysius in chapter 1 of The Celestial Hierarchy, for he says, the divine light can shine upon us only when screened round about by many sacred veils.² Hence, the soul, while united to the body, is capable of attaining a knowledge of separate substances only so far as it can be led thereto through species derived from phantasms. But in this way the soul will not attain quidditative knowledge of those substances, because their order of intelligibility transcends completely that of the intelligible species of material things abstracted from phantasms.

However, we can in this way attain some knowledge of those separate substances: we can know that they exist, just as from lowly and deficient effects we proceed to lofty causes, but only to the extent that we know they exist. And while we know that these superior causes exist, at the same time we know that they are not of the same nature as their effects, and this knowledge consists in knowing what they are not, rather than what they are. Consequently, it is true to say that, inasmuch as we grasp the quiddities which we abstract from material things, our intellect can, by turning to those quiddities, apprehend separate substances, so that it knows them to be immaterial, just as are the quiddities themselves which are abstracted from matter. Thus, thanks to the reflective power of our intellect, we are brought to a knowledge of intelligible separate substances. Nor is there cause for wonder if in this life we are incapable of knowing separate substances in their very essence, but we can know only what they are not.¹ For it is only in this way that we can know even the quiddity and nature of the heavenly bodies. Thus, in On the Heavens 1, Aristotle shows that the heavenly bodies are neither heavy nor light, generable nor corruptible, nor subject to contrariety.²

Whether the soul, when separated from the body, can understand separate substances

Seventeenth, it is asked whether the soul, when separated from the body, can understand separate substances.¹

Therefore, if the soul is unable to understand separate substances when it is actually joined to the body, it seems that the soul cannot understand these substances when it exists apart from the body.¹

Now the first manner of knowing cannot be found in souls existing apart from bodies, for that manner of knowing is proper to us so far as we derive our knowledge from the senses. Consequently, the separated soul understands in the second manner, namely, by proceeding from what is prior to what is subsequent; and then those things which are better known absolutely are known first by the soul. But that which is best known is the divine essence.¹ Therefore, if the separated soul knows separate substances by its nature, it seems that it can grasp the divine essence, which is life eternal, through natural things alone. This is contrary to the Apostle, who says, the free gift of God is eternal life in Christ Jesus our Lord (Rom 4:23).²

Moreover, the fact that souls existing apart from bodies know separate substances wherever they may be is in accord with reason.¹ For it is clear that the human soul, when joined to the body, has a direct knowledge of inferior things because of its union with the body.² Wherefore, the soul is perfected only by what it receives from inferior things, namely, by species abstracted from phantasms. Consequently, the soul can acquire a knowledge of itself and of other things only inasmuch as it is led thereto through the aforementioned species, as was explained above.³

However, when the soul really will be separated from the body, its vision will not be directed toward inferior beings in order to receive species therefrom, rather will it be independent and capable of receiving infused species from superior substances without turning to phantasms which will then be wholly non-existent. The soul will be actuated by infused species of this kind and thus will know itself directly by understanding its own essence, and not in an a posteriori¹ fashion as it does in its present state.² Moreover, by its essence the soul belongs to the genus of separate intellectual substances, although it is the lowest in this genus, and possesses the same mode of subsisting; for every separate substance is a subsisting form.³

Therefore, just as one separate substance knows another by immediately understanding its own essence, inasmuch as there is in its own essence some likeness of the other substance which it knows, either because it receives infused species from that substance, or from a superior one that is the common cause of both of them, so also does the separated soul, by immediately understanding its own essence, know separate substances by reason of the infused species received from them, or from the highest cause, namely, God.¹ However, the soul does not by its natural knowledge understand separate substances as perfectly as they understand themselves, because the soul is the most inferior of all intelligences and receives the emanation of intelligible light in the least degree.²

Eighteenth, it is asked whether the soul, when separated from the body, knows all natural things.¹

Furthermore (2), it might be said that he who sees a separate substance need not see all the species existing in its intellect.

Furthermore, everything that exists in the creature exists in a higher mode in God himself. For the natures and forms of things exist in creatures in many diverse modes, but in God they exist unitedly, in a simple and undivided way.¹ This existence of things is expressed in three ways:² first, God said, let there be a firmament, by which is understood the existence of things in the Word of God.³ Second, it is said, and God made the firmament, by which is understood the existence of the firmament in the angelic intelligence. Third, it is said, and it was so, by which is understood the existence of the firmament in its proper nature, as Augustine explains.⁴ The same applies to the other creations of God. For just as things flowed from God that they might subsist in their proper nature, so from the divine wisdom the forms of things flowed into intellectual substances so that those things might be understood.⁵

Hence, it must be borne in mind that the mode in which a thing exists in the order of natural perfection is the mode proper to it in the order of intelligible perfection. Now in the order of natural perfection singulars do not exist on their own account but for the sake of something else, namely, that in them the species to which they belong may be preserved. This indeed is what nature intends. For nature intends to generate man, not this man. Or rather, it generates this man only because the species cannot exist unless the individual man exists.

Thus, the Philosopher, in his work On the Generation of Animals, states that in assigning the causes of the accidents of a species we must go back to the final cause.¹ But the accidents of the individual, he says, must be reduced to the efficient or material cause, thus suggesting that only what pertains to the species as such falls under the intention of nature. Thus, knowledge of the species of things pertains to intellectual perfection, but not the knowledge of individuals, except perhaps accidentally.

Consequently, although this intellectual perfection is found in all intellectual substances, it does not exist in each of them to the same degree. For the intelligible forms of things exist in a more united and more universal mode in superior intellectual substances than they do in inferior intellectual substances where they are multiplied to a greater extent and are less universal according as they are further and further removed from the first simple being,¹ and come closer and closer to the particularity of things.² But thanks to their greater intellective power, superior substances perfect their intelligence through a few forms, so that they know the natures of things down to their ultimate species.³ Now even if forms as universal as those existing in superior intellectual substances were possessed by inferior substances, the latter would not thereby attain that ultimate intellectual perfection which consists in knowing things down to their individual species, because inferior intellectual substances have an inferior intellective power. Hence, their knowledge of things will remain more or less universal and indistinct, and generality and indistinctness are the marks of imperfect knowledge.⁴ For it is evident that the more active the intellect, the greater is its ability to acquire much from little. An indication of this is that things must be explained one by one to uncultivated people and to slow learners, and particular examples introduced for each single thing.⁵

Now the human soul is obviously the lowest among all intellectual substances. Consequently, it is capable by nature of receiving the forms of things in the material order.¹ Thus, the human soul is united to a body in order that the soul may receive intelligible species from material things through its potential intellect. Nor is its natural intellective power greater than that required for perfecting its knowledge through such forms. Hence, the intelligible light in which the human soul participates and which is called the agent intellect has as its function to actualize intelligible species of the type referred to.

Therefore, since the soul is united to the body, the soul’s vision is turned toward inferior things; from these it abstracts intelligible species proportioned to its intellective power, and it is in this way that the soul is perfected in knowledge. But when the soul is separated from the body, its vision is directed toward higher things alone, and from these it receives an influx of universal intelligible species. And although the species thus received have a less universal mode of existence in the separated soul than they enjoy in those higher substances, nevertheless the intellective power of the soul is not so efficacious that it can acquire a perfect knowledge of those intelligibles through this kind of species. That is to say, it cannot apprehend each one of them individually and determinately, but it can know them only generally and indistinctly in the manner in which things are known through universal principles. Moreover, separated souls acquire this knowledge all at once by an influx, and not successively by instruction, as Origen says.¹

Consequently, we must say that separated souls know all natural things in a universal way by natural knowledge, but do not know each of them individually. This is not the case, however, with respect to the knowledge that the souls of the saints possess through grace. For as regards that knowledge the saints are made equal to the angels inasmuch as they, like the angels, see all things in the Word.¹

The answers to the objections are now in order.

Reply Sed Contra 6: The separated soul is actualized with respect to all natural intelligible objects by a superior substance. However, it is not actualized perfectly but universally, as we have pointed out.¹

Reply Sed Contra 7: Although separate substances are in some way the exemplars of all natural things, it does not follow that all these are known when these natural things are known, unless the separate substances themselves are comprehended perfectly.¹

Reply Sed Contra 8: The separated soul knows through infused forms. But these are not forms of the order of the universe in an individual mode, such as superior substances possess, but only in a general mode, as was said.¹

Reply Sed Contra 9: Natural things exist in a certain respect in separate substances and in the soul. However, the forms of natural things exist actually in the separate substances, whereas they exist only potentially in the soul inasmuch as they are knowable.

Reply Sed Contra 10: The soul of Abraham was a separate substance. Consequently, the soul of the rich man was able to know the soul of Abraham, just as it could know other separate substances.

Nineteenth, it is asked whether the sensitive powers remain in the soul when it exists apart from the body.¹

Now it is evident that there is nothing contrary to the powers of the soul. Therefore, if they are corrupted, they are corrupted only by the corruption of their subject. Consequently, in order to discover whether the sensitive powers are corrupted when the body is corrupted, or whether they remain in the soul when it exists apart from the body, we must accept the principle of this investigation so that we may learn what the subject of the aforementioned power is. Now it is evident that the subject of a power must be that which is capable of doing something in virtue of its power, for every accident designates its subject.¹ Furthermore, an agent or a patient is nothing more than a thing which can act or undergo some change. Hence, whatever is the subject of an action or undergoes a change must be the subject of a power, the power itself being a principle. And this is what the Philosopher says in the book On Sleep and Sleeplessness, namely, that an action belongs to the thing to which the power belongs.²

Now there has been a diversity of opinion about the operations of the senses. For Plato held that the sensitive soul has a proper operation in virtue of its own nature, for he maintained that the sensitive soul is a self-mover, and that it moves the body only inasmuch as it is moved by itself.¹ Thus, there is a twofold operation in sensing: one by which the soul moves itself, and another by which it moves the body. Wherefore, the Platonists defined sense as the movement of the soul through the body.² For this reason, certain followers of this position distinguish two operations in the sensitive part of the soul, namely, certain interior operations by which the soul senses inasmuch as it moves itself, and certain external operations inasmuch as it moves the body.³ They also stated that there are two kinds of sensitive powers: some which are principles of acts within the soul itself, and which remain together with their activities in the separated soul when the body is corrupted; others, which are principles of external acts, and these are present in the soul and the body simultaneously and cease to exist when the body corrupts.

But this position cannot be held, for it is evident that anything whatever operates so far as it is a being.¹ Therefore, those things which exist of themselves, operate of themselves as individual substances. On the other hand, forms which cannot exist of themselves, but are called beings inasmuch as something exists by them, do not operate of themselves but are said to act inasmuch as their subjects act through them. For just as heat itself is not a thing having existence, but is that by which something is hot, so heat itself does not heat anything, but is that by which a hot thing heats something. Therefore, if the sensitive soul could operate of itself, it would follow that it would subsist of itself and thus would not be corrupted when the body is corrupted; but then the souls of brute animals would also be immortal. This is impossible, yet Plato is said to have conceded this.²

It is evident, then, that no operation of the sensitive part can belong to the soul alone in such a way that it can be exercised by the soul alone; but such operations belong to the composite because of the soul, just as the act of heating belongs to the hot thing on account of its heat.¹ Hence, the composite sees, hears, and senses all things, but it does this through its soul. Consequently, the composite is capable of seeing, hearing, and sensing, but it performs these because of its soul. Hence, it is clear that the powers of the sensitive part exist in the composite as their subject but come from the soul as their principle.² Therefore, when the body is corrupted the sensitive powers cease to exist, although they remain in the soul as in their principle. This is what the other position maintains, namely, that the sensitive powers remain in the separated soul as in their root.³

Twentieth, it is asked whether the soul, when separated from the body, knows singular things.¹

Therefore, this inquiry involves two difficulties: one common to intellectual nature as such, and one proper to human nature. The difficulty common to intellectual nature as such arises from the fact that our intellect does not seem to be capable of knowing singulars, but only universals. Therefore, since intelligence is the only cognitive power proper to God, to the angels, and to the separated soul, it appears difficult to see how they can possess a knowledge of singulars.

For this reason, some men made the mistake of denying any knowledge of singulars to God and the angels; but this is altogether impossible.¹ For if this position were adopted, divine providence would be excluded from things, the judgment of God concerning human acts would disappear, and the ministering of the angels would also be removed, for we believe that the angels are solicitous of the safety of man, as the Apostle says, are they not all ministering spirits sent forth to serve, for the sake of those who are to obtain salvation? (Heb 1:14).²

For this reason, some said that God, the angels, and separated souls as well, know the whole order of the universe through a knowledge of universal causes; for there is nothing in singular things that is not derived from these universal causes.¹ They offer the example that, if anyone should know the whole order of the stars and the heavens, and their measure and movement, he would know, by means of his intellect, all future eclipses, both their number, in what places they would occur, and at what time they would take place in the future.² But this is insufficient for a true knowledge of singulars. For it is clear that, no matter how closely universals may be united, a complete singular never results from their union—just as if I say man, white, musical, and will have added whatever others are possible, a singular will never result from them;³ since it is possible for all these universals, which are joined together, to belong to many men. Therefore, anyone who knows all causes universally never knows expressly any singular effect as a result of such knowledge. Nor does one who knows the whole order of the heavens know this eclipse inasmuch as it is this,⁴ for although he knows that a future eclipse will occur at such a position of the sun and moon, at such an hour, and whatever else is to be observed in eclipses of this kind, yet it is possible for an eclipse of this specific kind to happen many times.

Therefore, others, that they might ascribe a true knowledge of singulars to the angels, maintained that knowledge of this sort is derived from singulars themselves.¹ But this is quite incongruous;² for, since the greatest difference exists between an intelligible mode of existing and a material and sensible mode of existing, the form of a material thing is not received immediately by the intellect, but is carried to it through a number of intermediaries; for example, the form of a sensible thing first exists in a medium wherein it is more spiritual than in the sensible thing itself; next it exists in a sense organ, and from there it is drawn into the imagination and the other inferior powers; and finally it is carried to the intellect. Now it is inconceivable that such means should play any role either in the knowledge of an angel or in that of a separated soul.

Therefore, it must be said, on the contrary, that the forms of things through which the intellect knows are related to things in a twofold manner.¹ For some forms are productive of things, while others are derived from them; and forms which are productive of things lead to a knowledge of a thing inasmuch as they are productive of it. Thus, the artisan who gives the form to the thing made, or gives some disposition to matter, knows the thing made by the form of his art as regards that which he causes in the thing.² And because no human art causes matter, which is the principle of individuation, but receives matter already in existence, therefore the artisan—for example, a builder—knows the house in a universal way by its form, but he does not know this house as this house, except so far as he acquires knowledge of it through the senses. Now God, by his intellect, not only produces the form from which the universal account is derived, but also produces matter which is the principle of individuation.³ Consequently, he knows by his art both universals and singulars; for, as material things flow from the divine art, with the result that they subsist with their proper natures, so also by the same art do the likenesses of intelligible things flow into the separate intellectual substances, and these substances know the things produced by God, through these likenesses.

Therefore, the separate substances know not only universals, but singulars as well, inasmuch as the intelligible species which are infused in them by the divine art are the likenesses of things as regards both their form and their matter. Nor is it improper for a form which is productive of a thing, even though the form itself is immaterial, to be the likeness of a thing as regards both its form and its matter, because a thing always exists more simply in a superior nature than it does in an inferior one. Therefore, although form and matter are diverse in the sensible nature, nevertheless that which is higher and the cause of both is related to both as one existing thing; and, for this reason, superior substances know material things immaterially, and diverse things unitedly, as Dionysius says.¹ However, intelligible forms that are derived from things are acquired by abstraction. Hence, they do not give rise to knowledge of the thing as such, but only to a knowledge of what is abstracted from the thing. Therefore, since the forms in our intellect, which are derived from things, are abstracted from matter and from all material conditions, they do not lead to a knowledge of singulars, but to a knowledge of universals alone. This, therefore, is the reason why separate substances can know singulars by their intellect, whereas, on the other hand, our intellect knows only universals.²

Now an angelic intellect and a separated soul are differently situated so far as the knowledge of singulars is concerned. For we explained in a previous article that the efficacy of the angels’ intellective power is proportioned to the universality of the intelligible forms which they possess;¹ and, therefore, they know through universal forms of this kind all the things to which these forms extend. Therefore, just as they know all the species of natural things existing under their genera, so they know all the singular natural things contained under their species. However, the efficacy of the separated soul’s intellective power is not proportioned to the universality of infused forms, but, on the contrary, is proportioned to forms abstracted from things. For this reason, it is natural for the soul to be united to a body.² Therefore, it was said above that the separated soul does not know all natural things determinately and completely, even with regard to their species, but that it can know them in a certain general and indeterminate manner.³ Consequently, the infused species which separated souls possess are not sufficient for a knowledge of singulars to the point of enabling those souls to know all singulars as the angels do. Nevertheless, these infused species in the soul are limited to a knowledge of those singulars to which the soul is specifically ordered or inclined: for example, those things which act upon it, either things afflicting it, or things which leave impressions and traces upon it. For whatever is received is determined in the recipient in accordance with the condition of the recipient’s mode of being.⁴ Hence, it is evident that the separated soul knows singulars—not all singulars, however, but only some of them.

[No Reply to Objection 6 is provided.]¹

We must also answer those arguments which are raised as contrary objections, because they are false.

Reply Sed Contra 1: When the soul is joined to the body, it does not know singulars by its intellect directly, but by a certain reflection;¹ that is, inasmuch as it apprehends its intelligible, it turns back to consider its act, the intelligible species, which is the principle of its operation, and the origin of its species. In this way it proceeds to consider phantasms, and the singulars of which they are the phantasms. But this reflection can be completed only with the cooperation of the cogitative power and the imagination, which are not present in the separated soul.² Hence, the intellect does not know singulars in this way.

Twenty-first, it is asked whether the soul, when separated from the body, can suffer¹ punishment by corporeal fire.²

Now passion is used in two ways.¹ The first is to signify merely the reception of something, as when the intellect is acted upon by an intelligible, and a sense by a sensible. The second is to signify the loss of something on the side of the substance of the thing being acted upon, as when wood is acted upon by fire.²

Therefore, if the separated soul is acted upon by corporeal fire, in virtue of the divine power, inasmuch as the nature of passion consists merely in receiving something, it follows that the separated soul is receptive of corporeal fire in an immaterial and incorporeal way in keeping with the soul’s own mode, because whatever is received in something is received according to the mode of the recipient.¹

However, a reception of this sort does not punish the soul but perfects it.¹ Consequently, this will not be a punishment for the soul. Similarly, the soul cannot be acted upon by corporeal fire so far as passion consists in the loss of something on the side of the substance being acted upon, because then the substance of the soul would be corrupted. Therefore, the soul cannot be acted upon by corporeal fire as the instrument of divine justice.

Wherefore, it seemed to others that, although this fire is corporeal, nevertheless the soul does not suffer punishment by it directly, but by its likeness in the imagination;¹ this is just as happens to people asleep who are truly tormented by the appearance of certain terrible things which they see themselves suffer, although the things by which they are tormented are not real bodies, but merely the likeness of bodies. But this position cannot be maintained, because we have shown above that the powers of the sensitive part of the soul, of which one is the imaginative power itself, do not remain in the soul when it is separated from the body.²

Therefore, it must be said that the separated soul is acted upon by corporeal fire itself. However, it seems difficult to determine in what way it is acted upon by fire. For some said that the separated soul suffers by the very fire which it sees.¹ Gregory mentions this in Dialogues 4, saying, the soul suffers by fire in the very things which it sees.² However, since the act of seeing is a perfection of the one seeing, every vision is delightful inasmuch as it is of this sort. Hence, nothing is painful inasmuch as it is seen, but inasmuch as it is apprehended as harmful.³

Wherefore, others said that when the soul sees this fire and understands that fire is harmful to it, it is tormented by this fact.¹ Gregory mentions this is Dialogues 4, for he says that the soul is consumed by fire because it sees itself being consumed by fire.² But then we still have to discover whether fire by its very nature is harmful to the soul or not. Indeed, if it is not by its very nature harmful to the soul, then it follows that the soul is deceived in that judgment wherein it apprehends fire as harmful. This seems unlikely, particularly so far as the demons are concerned, because they possess an extensive knowledge of the natural order by reason of their intellectual acumen.³ Therefore, it must be said that corporeal fire in virtue of its true nature is harmful to the soul. Hence, Gregory concludes in Dialogues 4 by saying, we can gather from the aforesaid Gospels that the soul suffers not only by seeing fire but by experiencing it.⁴

Therefore, to discover how corporeal fire can be harmful to the soul or to a demon, we must bear in mind that harm does not befall a thing inasmuch as it receives something by which it is perfected, but inasmuch as it is hindered by its contrary.¹ Hence, the suffering of the soul by fire does not consist simply in its receiving something as the intellect suffers by an intelligible and sense by a sensible, but in this: that one thing is acted upon by another by way of contrariety and as an obstacle. Now this happens in two ways.

Sometimes a thing is hindered in one way by its contrary as regards its very act of existing which it receives from some inhering form; and in this way something is acted upon by its contrary through alteration and corruption, as wood, for example, is consumed by fire.¹

Second, a thing is hindered by an obstacle or a contrary with respect to its inclination, just as the natural inclination of a stone is to tend downward, but it is hindered in this by some obstacle and opposing power so that it is brought to rest or is moved contrary to its nature.¹

However, neither of these ways of suffering punishment exists in a thing that lacks knowledge. For where sorrow and sadness cannot exist, the account of affliction and punishment is not found. However, in a being which possesses knowledge, torment and punishment are the natural effects of both kinds of suffering, although in different ways. For the suffering which is the effect of change by a contrary results in affliction and punishment by sensible pain, as when a sensible object of the greatest intensity corrupts the harmony of a sense.¹ Therefore, when sensible things are of too great intensity, particularly those of touch, they inflict sensible pain, but when moderate they cause delight because then they are proportioned to sense. However, the second kind of suffering does not inflict punishment by sensible pain, but by that sadness which arises in a man or in an animal because something is apprehended by an interior power as being repugnant to the will or to some appetite.² Hence, things which are opposed to the will and to the appetite inflict punishment, and sometimes even more than those which are painful to sense. For some choose beforehand to be whipped and to undergo severe physical punishment rather than be scolded or the like, which is repugnant to the will.

Consequently, the soul cannot suffer punishment by corporeal fire according to the first kind of suffering, because it is impossible for the soul to be altered and corrupted by suffering of this specific kind. Hence, the soul is not afflicted by fire in this way, namely, that it suffers sensible pain thereby. However, the soul can suffer by corporeal fire according to the second kind of suffering, inasmuch as it is hindered from its inclination or volition by fire of this kind. This is evident. For the soul and any incorporeal substance, inasmuch as this belongs to it by nature, is not physically confined in any place, but transcends the whole corporeal order. Consequently, it is contrary to its nature and to its natural appetite for it to be fettered to anything and be confined in a place by some necessity; and I maintain that this is the case except inasmuch as the soul is united to the body whose natural form it is, and in which there follows some perfection.

Moreover, the binding of a spiritual substance to a body is not brought about by any power which a body has for detaining an incorporeal substance, but is the result of the power of some superior substance which unites a spiritual substance to such a body—just as by the magic arts, and with divine permission, some spirits are bound to certain things by the power of superior demons, either by signs or imaginary visions or other things of this kind. It is in this way, through the divine power, that the souls and the demons are confined in their punishment by corporeal fire. Wherefore, Augustine says in City of God 21, if men’s souls, having been created incorporeal, are now in this life incarnate in bodily members, and shall one day be bound thereto forever, then why cannot we truly say, though you may marvel at it, that even incorporeal spirits may be afflicted by corporeal fire? Therefore, these spirits, even though incorporeal, shall dwell in tormenting corporeal fires . . . and, instead of giving life to these fires, they shall receive punishment from them.¹

Thus, it is true that this fire, inasmuch as it detains the fettered soul, as a result of the divine power, acts upon the soul as the instrument of divine justice; and inasmuch as the soul apprehends that this fire is harmful to it, it is afflicted by interior sadness. Indeed, this sadness is greatest because the soul, which was born to be united to God through possession, meditates on the fact that it occupies a place below the lowest things in existence. Therefore, the greatest affliction of the damned will be caused by the fact that they are separated from God, and the second by the fact that they are situated below corporeal things, and in the lowest and meanest place.