Chapter 1

As all men naturally desire to know the truth, so there is in men, by nature, the desire to shun errors and to refute them when possessed of ability to do so. Among all errors, moreover, the one that seems to be especially unbecoming is the error about the intellect; for we have been born to know the truth by the power of this intellect through the avoidance of errors. Of late there has sprung up an erroneous doctrine about the intellect on the part of many men who take their starting point from certain works of Averroes. They assert that the intellect, which Aristotle called the possible intellect (he also inaptly called it "immaterial"), is evidently a kind of substance separate, by its very nature, from the body, yet in some way united to the body as its form; and further, that this possible intellect is one for all men. Against this doctrine we have already written much. But since the boldness of those in error has not ceased to assail the truth, it is our intention once more to direct an answer to this false teaching in order that its error may be manifestly confounded.

At this time it will not be our method to show that the aforesaid position is erroneous as being repugnant to the truth of Christian faith: this is at once sufficiently evident to anyone. For if there is no diversity of intellect among all men, and the intellect appears to be the only incorruptible and immortal part of the soul, then it follows that after death nothing of the souls of men survives except the one common intellect. Thus would be destroyed any possibility of retribution, of rewards and punishments, or any diversity in recompenses. However, we intend to show that their position is not less in conflict with the principles of philosophy than it is with the certain testimony of faith. Since for certain men concerned in this matter the words of the Latin philosophers have no savor, and since they claim to be followers of the Perpatetics (though of their books on this subject they have seen none, except those of Aristotle, who was the founder of the Peripatetic school), we shall point out that their position is altogether at variance with his words and express opinion.

First of all, there must be acceptance of the definition of the soul which Aristotle proposes in II De Anima, saying: "The first act of a physical, organic body." And lest, perhaps, someone may say this definition is not altogether applicable to all souls because of what Aristotle previously had conditionally stated; namely, "that it is necessary to predicate something that is common to all souls" (which they would understand to mean that such a thing cannot be), the following words of his must be noted. He says: "We have now given an answer to the question, What is soul—an answer which applies to it in its full extent. It is substance in the sense which corresponds to the definitive formula of a thing's essence. That means that it is the essential whatness of a body" (i.e., of a naturally organized body).

Lest it be thought that from this universal definition the intellectual faculty is excluded, this presumption is dispelled by what he afterward says: "The soul is inseparable from its body, or at any rate certain parts of it are—for the actuality of them is nothing but the actualities of their bodily parts. But, in truth, as regards other of its faculties, nothing prevents separation; since there are acts which belong to no body whatever." But this cannot be understood except of those acts that pertain to the intellectual faculty, namely, intellect and will. Wherefore it is clear that of the soul, which Aristotle had previously defined universally and called "the act of the body," certain faculties are the act of certain parts of the body; but other faculties are the act of no body. For it is one thing that the soul should be the act of the body, and another thing that a part of it should be the act of the body, as will be explained later. Hence also, in the same chapter, he shows clearly that the soul is the act of the body, since certain of its faculties are the act of the body, when he says: "One must consider in regard to the parts what has been said of the whole."

Moreover, in subsequent passages it appears even more clearly that the intellect is included under this general definition, as is shown by statements that follow. For, although he had previously given sufficient proof for the fact that the soul is the act of the body (since, if the soul is separated from it, the body no longer is in act as a living thing), he reiterates his position, because a thing may be called "actual" by the presence of a thing other than its form, if that thing were only an efficient cause; just as a combustible thing catching fire by proximity to something burning is "in act," and as a movable thing is "in act" when by the power of a mover it is set in motion. Hence doubt might arise in some one's mind as to whether the body is alive, or in act, by the effect of the soul's presence as any movable thing is moved by the power of an extrinsic agent, or whether it is in act as matter is, by its union with its form. There was a special need for Aristotle to clarify his position, since Plato had held that the soul was not united to the body as its form, but rather as a "mover" and "governor," as is evident from Plotinus and Gregory of Nyssa. I may certainly cite these men, since they were not Latins, but Greeks. The uncertainty of this problem, therefore, the Philosopher implies by what he afterward adds to earlier statements, saying: "We have no clear light on the problem whether the soul is the actuality of tis body in the same sense in which the sailor is the actuality of the ship."

Therefore since, even after previous explanation had been given, some doubt remained, he added a supplement, saying: "Thus figuratively a definition and description of the soul is given," because no one has yet demonstrated the truth to the point of certainty.

In order, therefore, to remove this doubt, he proceeds to reveal the things that are, of themselves and according to their nature, the more certain by means of the things that are less certain in themselves, but more certain as far as we are concerned; that is, he undertakes his demonstration through considering the effects of the soul, effects that are its acts. Hence he immediately makes distinctions in the operations of the soul, saying that an animate thing is distinguished from an inanimate by the fact of living, and that there are many things that pertain to life: namely, understanding, sensation, and change, both change of place and alteration connected with nutrition and growth; so that anything in which any of these characteristics is found may be said to "live." Furthermore, having shown how these powers are related one to another—how a being possessing one without the others is said to live, and how one can exist without the other—he concludes in this manner: The soul is the source of these phenomena and is characterized by them, namely, by the powers of self-nutrition, sensation, thinking, and motivity; and all these can be united in one and the same subject, as in man.

Moreover, since Plato had supposed that there were diverse souls in man according as different operations of life were found in him, he had inspired doubt whether each one of these were a soul, per se, or only a part of the soul; and if they were parts or faculties of the one soul, whether they differed only according to reason, or whether they were distinct according to place, that is, in organic location. And Aristotle added: "Regarding certain of these questions, there seems to be no difficulty, but others possess uncertainty." For, he pointed out, one thing is made clear about the things that pertain to the vegetative soul and the things that pertain to the sensitive soul by this fact: that plants and certain animals from which a part has been severed continue to live, and in each part all the operations of the soul which had gone on in the whole organism appear to endure. But of those questions that are doubtful he makes note when he says: "Concerning the intellect and power of foresight, nothing is yet distinctly evident." This statement he does not make because he wishes to show that the intellect is not a faculty of the soul, as the Commentator and his followers have perversely implied. For evidently this does not follow upon what he had previously said, that "some things, indeed, are uncertain." Therefore he must be understood to have meant that it is not as yet evident whether the intellect is the soul or part of the soul; and, if a part of the soul, whether it is distinct as to place, or only according to reason.

And although he says the matter is not yet clear, he subsequently adds what seems at first sight to be true: "But it seems that the soul is of another genus." Now, this ought not be interpreted as the Commentator and his school have perversely explained: namely, that he said this because the intellect is equivocally spoken of in regard to the soul, or because he could not harmonize his conclusion with the previous definition; but how it ought to be interpreted is evident from what follows: "In this respect it pertains to the intellect to be 'separate': namely, as the eternal is distinct or separate from the corruptible." In this, therefore, consists the fact that the intellect is another genus, because our intellect in this respect appears to be in a certain way eternal, but the other parts of the soul, corruptible. And because the corruptible and the eternal do not seem capable of union in the one substance, it seems that this one of the soul's faculties, namely, the intellect, should be separate, not indeed from the body (as the Commentator falsely maintained), but from the other faculties of the soul, and thus not communicate in the same way in the one substance of the soul.

That this should, in truth, be the interpretation is clear from what follows: "The other parts of the soul, it is evident, are not separable according either to substance, to reason, or as to place.'' Concerning this, inquiry had previously been made, and this, from the above cited passages, has been proved. Moreover, that the separability of the intellect should be regarded as meaning separability, not from the body, but that of the potentialities of the soul from one another, is evident from what follows: "It is certainly evident from reason that these powers are mutually distinct. Clearly, sensation is one thing, and opinion another." Hence he points out plainly by this determination his answer to the question proposed above. For the previous inquiry had been as to whether one part of the soul were distinct from the others according to reason only, or by actual location. Having dismissed this question as regards the intellect, concerning which he makes no definite answer, he says that, in regard to the other parts of the soul, it is clear that they are not separable as to location, but are distinct according to reason.

In maintaining that the soul is determined by its vegetative, sensitive, intellective, and motive powers, he wishes to show that in regard to all these faculties the soul is united to the body, not accidentally as a pilot in a ship, but as form is united to matter, that is, substantially. Thus it will be made manifest what the soul is in general, this manifestation having been made only in figurative language heretofore. Moreover, he further proves what the soul is by considering its operations as follows: Evidently that by which anything is first enabled to operate is the form of that operator just as we say we know by means of the soul and by means of science; although that we know by means of science is prior [in consciousness or reflection] to the fact that we know by means of the soul, because we do not know through the soul except in so far as it possesses science. Likewise we are said to be healed in body and in health, but in health primarily. Thus also it is evident that science is a form of the soul, and health a form of the body.

And in this way he proceeds. "It is the soul by or with which we live." This he says because the soul is vegetative; "and that principle by which we experience sensation," because it is sensitive; "and that by which we are moved," because it is capable of motion; "and that by which we think," because it is intellective. And he concludes: "Because it will ever be a certain nature and species, but not as matter and a subject." Evidently, therefore, as he said above, the soul is the act of the physical body, so here he concludes that it is not only the act of the vegetative, sensitive, and motive powers, but also the act of the intellect. Hence this was the opinion of Aristotle: that by which we understand is the form of the physical body. But, lest some one should think Aristotle did not say that that by which we understand is the possible intellect, but something else, then, plainly this is refuted by what he states in III De anima concerning the possible intellect. There he says: "By mind I mean that whereby the soul thinks and judges."

But, before we reach these words of Aristotle, which are in Book III of De anima, we should pause somewhat longer upon those remarks of his which are in Book II of De anima, so that from various statements assembled for comparison there may be clearly deduced what his opinion was about the soul. Now, after he had defined the soul in general, he began to distinguish its faculties; and he says: "The powers of the soul are vegetative, sensitive, motive, and intellective." That the intellective faculty is the intellect, he states clearly in what he adds later in explaining this division of powers: "One of them is, indeed, intellective, and is the intellect, as in men." He wishes, therefore, to make clear that the intellect is a power of the same soul which is the act of the body.

And that he had called the intellect a faculty of this soul; and, furthermore, that the definition of the soul is commonly inclusive of all its parts, is evident from his conclusion: "It is now evident that a single definition can be given of soul only in the same sense as one can be given of figure. For, as in that case there is no figure distinguishable and apart from the triangle, etc., so here there is no soul apart from the forms of soul just enumerated." Hence no other soul is to be sought for in addition to the ones already discussed, to which the definition of the soul given above is commonly applied. In the Second Book, Aristotle reveals nothing further of his theory about the intellect except that he adds, farther on, that ratiocination and understanding are the highest powers, and that they are also the least because, indeed, they are in very few creatures, as hereafter will be made clear.

But because there is a great difference in operation between the intellect and the imagination, he speaks in regard to the speculative intellect of "another nature"; yet he postpones discussion of this question to the Third Book. No one, however, should say (as Averroes falsely states) that Aristotle declares that there is "another reason" or "nature" in the speculative intellect because the intellect is not in the soul, or any part of the soul. This is immediately excluded as a possible interpretation in the beginning of the Third Book, where he resumes his discussion of the intellect; for he speaks here as follows: "Concerning that part of the soul, by which the soul possesses knowledge. and wisdom." Neither should anyone say, as some have dreamed of doing, that Aristotle says this only according as the possible intellect is distinguished from the active. For this passage occurs before Aristotle proves that there is a possible as well as an active intellect; wherefore he speaks here of the intellective part of the soul in common, according as it comprises both the active and the possible intellects (even as in, the Second Book he clearly distinguishes the intellective from the other parts or faculties of the soul, as has been said).

Moreover, the admirable precision and order of Aristotle's method of procedure must be observed. Now, in the Third Book, he begins his treatise concerning the intellect, which, in Book II, he had left undecided. There he had previously allowed two things to remain uncertain.

First, the question whether the intellect is distinct from the other faculties of the soul only according to reason, or whether it is also distinct as to location. This he had dismissed indefinitely when he said: "We have no evidence as yet about mind or the power to think."

This position he at first resumes when he asks: "Whether in existence it is separable (from other parts of the soul), or is inseparable from the quantity of the body but distinct or separable according to reason." In this passage he employs the phrase, "secundum magnitudinem" to indicate what he had previously spoken of as "separabile loco."

Secondly, he had left in uncertainty the difference of the intellect as compared to the other faculties of the soul, when in conclusion he said: "In regard to the speculative intellect, however, there is another nature." This he straightway questions when he says: "What kind of difference the intellect possesses must be considered." He undertakes to assign it such a difference as could stand according to both of the premises already proposed: namely, whether the soul is separable spacially in respect to certain parts of the body, or not; and this intention he himself plainly enough indicates by his manner of speaking: "Turning now to the part of the soul with which the soul knows and thinks (whether this is separable from the others in definition only, or spacially as well) we have to inquire what differentiates this part and how thinking can take place." From this it is evident that he did not intend to show that the difference was one of substantial separation from the body; for this position could not be maintained in view of both the alternatives proposed, but he intended to assign to the intellect a difference in mode of operation. Hence he continues: "And according to what manner it comes to understand." Consequently, by means of those statements which we are able to gather from the words of Aristotle himself, it is evident, thus far, that he wished the intellect to be regarded as a faculty of the soul, which is the act of the physical body.

But since, from certain other words, Averroes has tried to make it appear that Aristotle meant that the intellect was not the soul, which is the act of the body, nor any part of such a soul, further statements must also be attentively considered. Immediately after raising the question as to the difference between the intellect and sensation, Aristotle inquires in what way the intellect is like the senses and in what way it differs from them. Now, previously he had concluded two things about sensation: namely, that a sense is in potency to sensible objects, and that a sense is impaired or even destroyed by the excellence of sensible objects. On this point, therefore, Aristotle makes inquiry, saying: "If to understand is the same as to experience sensation, or to be passive to something, then in the same way the intellect will be passively impressed by its intelligible object, and will be overpowered by the excellence of that object, just as the senses are by the too-great excellence of sensible things, and in like manner of other things." Thus the question is this: Is the act of understanding something quite similar to that of experiencing sensation, or is it, on the contrary, different in this respect, that it is not passible?

To this question, he immediately answers (deriving his conclusion not from previous statements but from those which he makes subsequently, which later statements are, however, clearly evident from an analysis of the former) that this part of the soul ought to be impassible and not subject to the same alteration or corruption as the senses. Yet it has a certain passivity, but this is of another sort, according as the term, "to understand," commonly means "to be passive." In this respect, therefore, it differs from sensation. But at the same time he shows how it agrees with sensation: for, indeed, this part must be capable of impression by intelligible species and be in potency to species of this kind, and not, by its own nature, in act—even as he had previously stated that a sense is in potency to sensible objects and not, of itself, in act. From this he concludes that the intellect must be related to intelligible objects just as a sense is to sensible things.

Now, he stated this in order to reject the opinion of Empedocles and other ancient philosophers who taught that the knower is of the same nature as the thing known, so that, being composed of earth, we know earth, and being also of water, we know water. Aristotle, however, had shown previously that this is not true in regard to the senses, because a sense faculty is not in act, but only in potency to that which it experiences as a sensation; and the same, he says, obtains in regard to the intellect.

There is, nevertheless, this difference between the senses and the intellect: that each sense is not capable of experiencing all sensations, but sight is in potency only to color, hearing to sound, and so of the others; whereas the intellect is, absolutely, empowered to know all things. The ancient philosophers, thinking that the knower had to possess the same nature as the object known, had said furthermore that this fact, that the soul was capable of knowing all beings, must be on account of its being composed of the principles of all things. But, because Aristotle had now proved by comparison with sensation that the intellect is not in act as regards what it comes to know, but in potency only, he concludes, on the contrary, that since the intellect knows all things, it must be without any mixture; that is, not composed of all the elements, as Empedocles had stated.

To support this theory, he also calls upon the testimony of Anaxagoras, even though he had spoken not of this same human intellect, but of that mind (Nous) which moves all things. But just as Anaxagoras had declared that that intellect, in order to govern all things by setting them in motion and keeping each in its proper course, must be simple, or unmixed, so we can say of the human intellect that it must be simple in order to know all; and this Aristotle consequently proves, and the Greek text says: "Now, that which is within, evidently hinders and prevents the extraneous from entering, as can be understood by a comparison with vision." For if there should be any color intrinsic to the pupil of the eye, that interior color would prevent the seeing of the color outside, and in some manner hinder the eye from seeing other things.

Likewise, if any nature of those things which the intellect knows—for example, earth or water, warmth or cold, or anything else of the sort—were intrinsic to the intellect, that intrinsic nature would be an obstacle to the intellect, and in some way prevent its knowing other things.

Since, therefore, the intellect does know all things, Aristotle concluded that it could not possess any determinate nature derived from the natures of sensible things which it knew, but that its nature was constituted by this alone, that it must be possible of determination; that is, that as regards its nature it must be in potency to those things which are intelligible, but become active by understanding them in act; just as the senses are made to be in act by the sensible in act, as he had previously said in the Second Book. He concludes, therefore, that the intellect, before understanding renders it "in act," is not actively any of the things which exist—a conclusion which is contrary to what the ancients claimed: namely, that it was actually all things.

Moreover, because he had mentioned the statement of Anaxagoras in which he speaks of that intellect which governs all things, Aristotle, lest anyone believe that he had drawn his conclusion about that same intellect, employs this manner of explanation: "Anaxagoras called this the soul's intellect. I speak, however, of that intellect by which the soul thinks and understands, which is actively none of those things which exist before they are understood." From this, two facts are evident.

First, that he certainly is not speaking here of an intellect which is some kind of separate substance, but of the intellect which, as he said above, is that power and faculty of the soul by which the soul understands.

Secondly, the fact that he had previously proved; namely, that the intellect has no nature which is determinate in act.

He has not yet proved that it is not a power existing in a body (as Averroes says), but this he immediately concludes from the foregoing, when he says: "Therefore the rational faculty has no admixture of that which is corporeal." This second statement he proves by means of the first, which he previously explained: namely, that the intellect possesses actively none of the natures of sensible things. From this it is evident that there is in it no union with anything corporeal; for if it were intermingled with some bodily substance, it would possess some kind of corporeal nature. And he adds: "For indeed, a thing would become some kind of thing, either warm or cold, if it were united to a bodily organ, Just as m the case of the sensitive faculties." Now, each sense is proportioned to its own organ and is bound, as it were, or restricted to its own nature. Hence according to the immutability of the organ, the operation of each sense is immutable. Thus, therefore, he understood that the intellect was not blended with the body; namely, that it has no organ as have the senses.

Moreover, that the soul's intellect has no organ is clear from the statement of those who say that the soul is the locus of the intelligible species (accepting the term "locus" broadly in the sense of Plato, as meaning that which is all-receptive); unless to be the locus of the species is not proper to the whole soul, but to the intellect alone. For the sensitive part of the soul does not receive species into itself, but in an organ. The intellective faculty, however, receives them in no organ, but in itself. Moreover, the locus of the species is not such that it possesses these in act by its nature, but that it is in potency to possess them.

Since, therefore, he has shown what befits the intellect, by means of comparison with the senses, he now returns to what he had first said: that the intellective faculty must be capable of receiving species; and so, with admirable subtlety, by means of a likeness, he concludes to dissimilarity. Hence he subsequently shows that the passibility of the senses and that of the intellect are not similar by the fact that a sense faculty is disturbed by the excellence of a sensible object, but the intellect is not overpowered by the excellence of its intelligible object. The reason of this he assigns as derived from the preceding discussion: namely, that the sensitive faculty is not incorporeal, but the intellectual is, being "separate."

This last word, "separate," some have especially seized upon as a prop for their error, for they would interpret him to mean by it that the intellect is neither the soul nor a faculty of the soul, but a separate substance; but they too quickly forget what Aristotle said but a little before. Now, just as here he says that the sense faculties are not incorporeal, but the intellect is separate, so previously he had said that the intellect would be of a certain quality, either warm or cold, if it possessed any organ, as the sense faculties do. By this method of reasoning here, he is stating that the senses are not incorporeal, but the intellect is "separate," since a sense faculty has an organ, but the intellect has not. Most evidently, therefore, it appears from the words of Aristotle that, without any doubt, this was his opinion about the possible intellect: namely, that the intellect is some part of the soul, which is the act of the body; but that, nevertheless, the soul's intellect has no corporeal organ, as have the other powers of the soul.

Moreover, how this can be—that the soul is the form of the body, and yet that some power of the soul should not be a power of the body—is not difficult to understand if we consider that same situation in regard to other things. For we see, in many cases, that a certain form is the act of a body composed of a mixture of elements, and yet it has a certain power which is not that of any of those elements, but which belongs to such a form from some other principle: namely, from a heavenly body, just as a magnet has the power of attracting iron, and jasper has the power of checking the flow of blood. And we see that, by degrees, those forms which are the nobler possess powers which more and more exceed those of matter. Wherefore the highest of forms, which is the human soul, possesses one power which altogether transcends the material body: namely, the intellect. In this way, therefore, is the intellect "separate," since it is not a corporeal power, but a power in the soul; though this same soul is the act of the body.

Neither do we say that the soul, in which the intellect resides, so excels its material body that it does not require to be in a body, but only that the intellect, which Aristotle calls a power of the soul, is not the act of the body. Nor is the soul the act of the body through the mediation of its faculties, but it is itself, per se, the act of the body, giving to it its specific nature; whereas some of its faculties are the acts of certain parts of the body, perfecting them as regards certain operations. Thus that faculty which is the intellect is the act of no part of the body, since it requires no corporeal organ.

And lest it seem to anyone that I say these things according to personal interpretation, departing from the intention of Aristotle, the words of Aristotle himself can be cited which expressly state the same opinion. For, in II Physic. he asks just how far one ought to know a species and what a thing is: For it does not pertain to physics to study every form. He subsequently gives as his answer: "In the same way as a physician must know a nerve, or as the smith must know bronze: that is, in view of a certain end." And to what "end" he has reference, he later shows: "In view of whatever the purpose of each is." This is as if he would say: The physician studies the nerve only inasmuch as it pertains to the health, on account of which the physician considers the nerve; and likewise, the smith considers the bronze only in view of his craft; and since the physician considers the form so far as it is in matter—for thus it is the form of a body subject to change—in like manner, it must be understood that natural science considers a form only inasmuch as it is in matter.

The terminus of the physicist's consideration of forms is in those forms which are in matter after a certain fashion, but which, in another way, are not in matter. For these forms are on the boundary line of separate and immaterial forms; wherefore, he adds: "Regarding this, the consideration of the physicist is, indeed, of forms which are separate, but as they are specific forms in matter." What these forms are, he indicates, saying: "Man generates man from matter,—man, that is, and the sun." The form of man, therefore, is in matter and yet separate. It is in matter inasmuch as it gives existence to the body, and thus it is, indeed, the cause of generation; but it is separate as regards that faculty which is properly that of man: namely, the intellect. It is not impossible, therefore, that a form should be in matter and that a faculty of it should be separate, as has been shown in respect to the intellect.

There are still some, however, who undertake to show in another way that the opinion of Aristotle was that the intellect is not in the soul, that it is not a faculty of the soul which is united to the body as its form. In many places, Aristotle says that the intellect is eternal and incorruptible, as, for example, he declares in II De anima: "This befits a separate form alone, as eternal is distinguished from corruptible." And in Book I, where he says: "The mind seems to be an independent substance, and to be incapable of being destroyed." He has also stated in Book III: "The separated form alone is that which truly is, and this only is immortal and eternal." This last quotation, however, some do not apply to the possible, but to the active intellect. From all these passages it is clear that Aristotle wished it understood that the intellect is something incorruptible.

Yet it seems that nothing incorruptible could be the form of a corruptible body. For, indeed, it is not accidental to this form, but pertains to it essentially to be in matter; otherwise from the union of matter and form there would result only an accidental whole. But nothing can exist without that which belongs to it essentially; consequently the form of the body cannot exist without the body. If, therefore, the body also is corruptible. Furthermore, forms separated from matter, and forms existing in matter, are not of the same species, as is proved in VII Metaph. Much less, therefore, can one and the same form, numerically, be now incorporeal, and now in a body. Hence, if the body is destroyed, the form of the body either will be destroyed or will pass into another body. If, therefore, the intellect is the form of the body, it seems to follow of necessity that the intellect is corruptible.

Now, it must be noted that this manner of reasoning influenced many philosophers: Gregory of Nyssa, for example, interpreted Aristotle in a contrary way by supposing that, because he had said that the soul is the form of the body, he judged it to be corruptible. Certain others, moreover, because of this same statement, have supposed that the soul migrates from one body to another. Still others have held that the soul possesses some kind of incorruptible body from which it is never separated. Hence it must be shown from Aristotle's words how it was that he judged that the soul was the form of the body, and yet judged also that it was incorruptible.

In XI Metaph., after he had explained that forms are not antecedent to their matter—because, just as at the time when a man is healed, simultaneously there is health; and as the figure of a bronze sphere is simultaneous with the bronze figure—he next inquires whether any form remains after the corruption of the matter, and he answers in the affirmative, according to the opinion of Boethius: "But it must be considered whether, in truth, anything does remain afterward apart from the matter. In certain cases nothing would hinder this being so, if the soul were of this order: that not all of it would remain—for, perhaps, that would be impossible—but that the intellect, of all its powers, would remain." Hence, it is evident, he says, that nothing would prevent the intellectual faculty of the soul, which is the form, from remaining after the body, even though it did not exist before the body. For, although he had said, absolutely, that efficient causes are antecedent, but not formal causes, he does not question whether any form might exist prior to matter, but whether any form could remain after matter; and he says that nothing would hinder this on the part of that form which is the soul as regards its intellectual faculty.

Since, therefore, according to the foregoing words of Aristotle, this form which is the soul could continue to exist after the body-not in its entirety, but the intellect-it remains to consider why the intellectual part of the soul should survive the body rather than the other faculties, and rather than other forms which do not survive their matter. The reason of this, indeed, can be gathered from the words of Aristotle himself. For he says in III De anima: "The separate [form] is that alone which truly exists, and that alone which is immortal and eternal." He seems, therefore, to assign this as a reason: that since the intellect alone seems to be immortal and eternal, it alone is separate.

But concerning what intellect it is that he here speaks of, there can be doubt. According to some, he is speaking of the possible intellect; according to others, of the active. But, that both these groups of interpreters are mistaken is evident if the words of Aristotle are considered attentively. For both the possible and the active intellect Aristotle had called "separate." It is certain, therefore, that anything he may say of either the active or the possible intellect individually can be understood as applying to the whole intellectual faculty, since it possesses no corporeal organ of operation, as is evident from Aristotle's own words.

Moreover, Aristotle had said in I De anima: If there is any way of acting or being acted upon proper to soul, soul will be capable of separate existence; if there is none, its separate existence is impossible. Rather [its existence] is that with which it shares a common nature. Since everything operates inasmuch as it exists as a being, so the mode of the action of each thing is conformed to its mode of existence. Therefore forms that have no operation except in conjunction with their matter do not themselves act; but it is the composite that acts through its form. Wherefore forms of this kind, properly speaking, are not; but something is possessed by them. In the same way as heat does not warm, but something hot warms; so also heat itself does not exist by means of that which has heat, properly speaking; but that which possesses heat does exist through that which is heat-in-itself. On this account, Aristotle says in X Metaph. that it is not truly said of accidents that they are "beings," but more truly that they are "of a being";

and the same reasoning is employed about substantial forms that have no operation when not united with matter, except that the principle of substantial existence belongs to this form. Therefore a form that possesses an operation of its own, according to any of its faculties, or a power independent of matter, is subsistent; nor does it exist by means of the existence of the composite, as do other forms, but rather the composite exists through it. Hence, if a composite is destroyed, that form which possesses existence from the composite is likewise destroyed. On the other hand, it would not follow that the destruction of a composite would bring about the destruction also of a form by whose existence the composite exists, and which does not owe its existence to that of the composite.

If, however, some one objects that Aristotle (I De anima) says: "To understand and to love and to hate are not its activities, not phenomena of the soul, but activities of him possessing the capacity to know and to love and to hate. Wherefore in case of corruption the soul neither remembers nor loves, for these things do not belong to it properly, but were common attributes, as the saying is"—then an answer is provided by the statement of Themistius who, commenting on this says: "Aristotle here assumes more the attitude of one in doubt than of one teaching authoritatively." Now, at this point, he had not yet refuted the opinion of those who said that the intellect and the senses are not different;

wherefore in this entire chapter he speaks of the intellect as of a sense faculty. This is particularly apparent where he proves the incorruptibility of the intellect by the example of a sense faculty that is not impaired by old age. Hence throughout he speaks conditionally and in a way to imply doubt as if seeking an answer, always linking things that pertain to the intellect with mention of the senses—a fact made especially evident by what he says in the beginning of this discussion: "We may admit to the full that being pained or pleased, or thinking, are movements (each of them a 'being moved')." If, however, anyone holds that Aristotle is speaking precisely, there remains this reply: that to understand is said to be an act of the intellect united to the body, not per se, but per accidens, inasmuch as the object of the intellect (the phantasm) is in a corporeal organ; but the act of the intellect is not exercised through a corporeal organ.

However, someone may inquire further and ask: "If the intellect is incapable of understanding without the phantasm, how will the soul have any operation after it has been separated from the body?" We reply that whoever raises this objection ought to know that the solution of this problem does not pertain to natural philosophy. Hence, in II Physic., when speaking of the soul, Aristotle says: "How the separable form will be related to other things, and what kind of being it is, is the task of first philosophy to determine. Now, the separated soul must be judged to possess a mode of knowledge other than that which the soul has while conjoined with matter"—a knowledge like that of other separate substances. Therefore, not without reason, Aristotle inquires, in III De anima, whether an intellect not separated from spacial magnitude can know anything that is separate.

By this question he gives us to understand that the separated intellect is able to understand something which the intellect which is not separate is incapable of knowing. In these same words, moreover, it is to be noted that, whereas he had formerly called both the possible and the active intellect "separate," so here he speaks of both as "not separate." For they are "separate" to the extent that their acts are, not the acts of any corporeal organ; yet they are "not separate" in that each is a faculty or power of the soul, which is the act of the body, as has previously been said. Furthermore, it is most certainly possible to show that Aristotle solved questions of this kind in those books which, from what he says in the beginning of XII Metaph., we are sure that he wrote concerning separated substances; and of these books I have seen fourteen, though they have not yet been translated into our language.

Accordingly, it is clear that his reasoning involves no necessary contradiction: It is essential to the soul that it should be united to a body, but by this it is restricted only accidentally, not on its own part, but on the part of the body, which is corruptible; just as, per se, bodies that are light or subtle have their place above the heavier, and it is essentially characteristic of these light bodies so to exist on high. But, as Aristotle says in VIII Physic., it may happen that on account of something weighing it down, such a body would, nevertheless, not be in its proper, higher place.

In this way, he offers the solution of the other difficulty. For, just as that which has a nature to be above other bodies differs specifically from that which does not have the nature to be so; and as that which essentially is thus subtle has its own same nature, numerically and specifically, whether it is in its proper place above others, or whether, on account of some impediment, it is not, so also two forms differ specifically if one of them has the nature to be united to a body and the other has not. Nevertheless, that having the nature to be united to a body will be, numerically and specifically, one and the same form both when it is actually united to a body and when, on account of some interference, it is not actually so united.

However, some still bring up, as a prop for their error, what Aristotle says in his book, De generatione animalium: "The intellect alone comes from without and it alone is divine." Now [those proposing the objection say that] no form which is the act of matter comes to that matter from without, but it is educed from the potency of matter. The intellect, therefore, is not the form of the material body.

They also say by way of objection that any form of a mixed body is caused by the elements; therefore, if the intellect were the form of the human body, it would not come from outside, but would be produced by its elements.

Some object further that it would follow that the vegetative and the sensitive souls would also be of extrinsic origin—a statement contrary to the opinion of Aristotle—especially if it is maintained that there is but one substantial soul whose powers are vegetative, sensitive, and intellective; since, according to Aristotle, the intellect is from an extrinsic source.

The solution of this difficulty, however, is at once evident from what has previously been said. For, although he said that any form is educed from the potentiality of matter, the phrase, "educed from the potentiality of matter," may be taken in two ways. In the first place, a form may depend on matter both for existence and for its operation; but, in another way, it may mean that matter must exist prior to form. Now, if the meaning is only that matter shall precede the form, it seems that the form could be considered to be "educed from the potentiality of matter." For if this is to say nothing else than that matter pre-exists in potentiality to a form, nothing hinders one from saying that corporeal matter pre-exists in potentiality to an intellectual soul, whence Aristotle in De generatione animalium says: The vegetative soul must be considered to be potentially possessed in semination and conception, before separation from the parent; but such souls are not in act until, having been conceived, they become separated, procure food, and carry on the functions of such a soul. For, in the beginning, these appear to have all their life as the life of the parent.

The same must be said also of the sensitive soul, and even of the intellectual. For, necessarily, all these souls must be considered to be in potency before they are in act, so that it may not have the same meaning for them to be "in potency" and "in act." Now, it has been shown, in regard to those forms that have no operation apart from their union with matter, that they ought to be such in the act by which they exist as that with which they are combined or mingled, and with which they co-exist, since they possess the selfsame existence; wherefore, as their total existence is directed toward concretion in matter, so they are said to be totally educed from the potentiality of matter. The intellectual soul, on the other hand, since it has an operation apart from the body, has not an existence directed solely toward concretion in matter. Wherefore it cannot be said to be educed from matter; rather, it exists by reason of an extrinsic principle. This is apparent from these words of Aristotle: "It must be concluded, however, that the intellect alone comes from without, and it alone is divine." And the reason for this conclusion he assigns when he says: "For no bodily operation shares in its operation."

However, I wonder at the source from which a second objection proceeds, namely, "If the intellectual soul is the form of a mixed body, it must be caused by a mixture of the elements, whereas no soul is caused by a commingling of elements." Now, Aristotle says, immediately after the foregoing words: "But every power or potency of the soul seems to participate another kind of body than those called the elements—one of a more divine nature. Truly, inasmuch as souls differ among themselves as noble from ignoble, so also the natures of bodies differ. For there is in the generating principle of all things that which makes them to become fecund principles of generation: for example, that which is called heat is not fire, nor any property of it, but a 'spirit' which is contained in the generating principle and in the seminal vapor; and the nature which is in this spirit corresponds proportionately to the elements composing the stars." Therefore, from a mingling of elements not the intellect only, but not even the vegetative soul is produced.

The difficulty which the third objection proposes, namely, that it would follow that the sensitive and vegetative souls would also have existence from without, by an extrinsic principle, if the intellective soul has, is not relative to the discussion. For it is clear from Aristotle's words that he left it uncertain, whether the intellect differs from the other faculties of the soul both as to subject and as to location, as Plato held, or whether they are only logically distinct [i.e., according to reason]. But if it is granted that they are the same as regards their subject, as is the more probable, then there is no difficulty. For Aristotle says in II De anima: "The cases of figure and soul are exactly parallel." For always, in that which exists with greater complication (consequenter)—whether in geometric figures or in living things—there exists potentially that which is simpler, or prior; just as in a square, a triangle exists in a certain way, and in a sensitive being, that which is vegetative.

That the intellect, in a similar way, exists in the same subject, he leaves in doubt. But it can be said that the vegetative and sensitive soul are in the intellective, just as a triangle and square are in a pentagon. Now, the square is indeed, absolutely speaking, an altogether different figure in species from a triangle, but not from a triangle which is contained potentially within it; just as four sides of a square are not specifically different from the three sides of a triangle which are a part of the same figure, though it is distinct from the triangle, existing independently. And if it would happen that diverse figures would be produced by different agents, a triangle existing independently of a square could have the same producing cause as the square and still have a different species of its own; but the triangle which is in the square would have the same producing cause. Thus, therefore, a vegetative soul existing apart from a sensitive soul is specifically of another kind and has another producing cause. Nevertheless, in the case of a vegetative soul existing in a sensitive soul there is the same producing cause for both sensitive and vegetative. If, therefore, it is said that the vegetative and sensitive souls which are in the intellective have consequently an extrinsic cause, no difficulty ensues. For it is not inconsistent that the effect of a superior agent should have the same power as the effect of a lesser agent, yet, at the same time, possess additional powers of its own. Therefore also the intellective soul, although it has its origin from an extrinsic agent, has the same powers that a vegetative soul and a sensitive soul possess, even though these souls may be caused by interior agents.

Thus, therefore, after a most careful examination of almost every word that Aristotle spoke about the human intellect, it seems that his judgment was this: The human soul is the act of the body, and one of its faculties or powers is the possible intellect.