Chapter 5

It remains now to deal with those objections by which our opponents seek to exclude a plurality of possible intellects. Of these objections, the first is that any form which is multiplied according to division of matter is a material form; wherefore there cannot be a plurality of separated substances in the one species. Hence, if there should be many intellects in many men numerically distinguished by division of matter, it would follow necessarily that the intellect would be a material form; but this is contrary to the statement of Aristotle and to his argument proving that the intellect is separate. If therefore it is separate and is not a material form, it can in no way be multiplied according to multiplication of bodies.

To strengthen this reason, some bring forward still another in saying that God could not create many intellects of the same species in diverse men. They say, indeed, that this implies a contradiction, because to have matter and to be numerically multiplied is opposed to the nature of a separate form. They even proceed beyond this, trying to conclude that a separate form is not numerically one, or an individual thing. However, their error seems to be owing to a matter of vocabulary: for they say a thing is not numerically (numero) one unless it is one of many (de numero). A form that is independent, or free of matter, is not one of many, since it has in itself no cause of plurality; for the cause of number is in matter.

On the contrary, in order that we may make a beginning from the latter part of their argument, we point out that our opponents seem to be ignorant of the proper sense in which the last statement was made. For Aristotle said, in IV Metaph.: The unity of the being of any substance is not accidental, and nothing is a unity except being. A separated substance, therefore, if it is a being, is one according to its substance; especially since Aristotle says in VIII Metaph.: Those things that have no matter, have no cause that they should be one and being. The term "unity," however, is used in V Metaph. to indicate four kinds of unity: namely, numerical, specific, and generic unity, and the unity of proportion. Now, it cannot be said that any separated substance is one only specifically or generically; for this is not to be one simpliciter. It remains, therefore, that every separate substance is numerically one. But "one" does not mean that a thing is numerically one because it is one of a number; for number is not the cause of the unity of a being. On the contrary, a being, since it is not divided, ranks among things that are numbered. For "one" is that which is not divided.

Nor again, is this true: that any number is caused by matter. If this were so, Aristotle would have inquired vainly in regard to the number of separate substances. Moreover, Aristotle also states in V Metaph.: Multitude is divided not only by number, but also by species and genus. Neither is it true that a separate substance is not anything singular or individual; for in that case, it would have no operation, since "act is only of singulars," as the Philosopher says. Wherefore, opposing Plato, he says in VII Metaph.: If the ideas were separate, one idea would not be predicated of many, nor could any of them be defined; just as no other being which is the only one of a species can be defined: for example, the sun and the moon. Matter, indeed, is not the principle of individuation in material things except in so far as it cannot be participated by many individuals, since it is a "first subject," not existing in another; wherefore also, speaking of the ideas, Aristotle says: If the ideas were separate, each would be an individual substance that could not be predicated of many.

Separate substances, therefore, are individual and singular. However, they are not individualized by matter, because they are not so produced as to require to be in another, and consequently do not have to be participated in by many. Hence, if any form is produced to be participated in by another, in such a way that it is the act of certain matter, that form can be individualized and multiplied by reason of its relation to matter. We have shown previously, however, that the intellect is united to the soul, which is the act of the body. In many animate beings there are many souls, and in many souls there are many intellectual powers, which are called "intellects." But it does not follow on this account that an intellect is a material power, as has already been proved.

Someone may object that, if numbers of souls are multiplied according to the numbers of bodies, then, when the bodies have been destroyed, a plurality of souls will no longer exist. The answer to such a difficulty is evident from what has already been stated. For everything is one inasmuch as it is being, as is said in IV Metaph. Thus, although the existence of the soul is in the body, inasmuch as it is the form of the body (nor does it exist before the body), nevertheless, when the body has been destroyed, the soul still remains in possession of its own existence, in such a way that each soul perseveres in its own unity; consequently many souls remain, constituting their own multitude.

Certainly, however, those others who try to prove that God could not create many intellects of the same species, present a clumsy argument, believing that this would involve a contradiction. Now, though we should grant that it is not of the nature of an intellect to be multiplied, we cannot presume that for such an intellect to be multiplied would imply a contradiction. For even though the cause of some quality would not be in the nature of a being, still nothing would prevent its possessing this perfection from some other cause; just as a heavy body has the tendency by its own nature not to be above lighter bodies; nevertheless, for such a heavy body to be thus above does not involve a contradiction; though to be thus above would be, according to its own nature, contradictory. Thus, even if the intellect, by nature, were one for all men because of not having any natural cause for multiplication, still this multiplication could be allotted to it by a supernatural cause: nor would this imply any contradiction. This fact we emphasize, not only in view of the immediate problem, but more in order that the same argument may not be extended to other discussions. For, in the same way, one might be able to conclude that God could not cause the dead to rise, and that sight could not be restored to the blind.

Still another reason is adduced by some in support of their error. For they inquire whether the intellection in me and that in you are altogether and perfectly one, or whether they are two in number and one in species. If one, then there is but one intellect; if numerically two, though one in species, then it will follow that the things intellected will possess the intelligible object. For whatever things are two in number and one in species are understood as one, because there is but one essence by which they are understood; and so one arrives at progression to infinity, which is impossible. Therefore [they say] there cannot be two things numerically intellected—one in me and the other in you. Hence there is but one thing understood, and only one intellect, numerically the same, in all men.

But the question must be asked of those who think that they argue so subtly, whether for two intellects to be numerically distinct, yet one in species, is contrary to the nature of intellect, as intellect, or inasmuch as it is the intellect of man. According to the reason which they advance, it is evident that they mean it is contrary to the intellect as an intellect. For it is according to the nature of the intellect as such, that it should lack nothing that constitutes it as an intellect. Therefore, according to their reasoning, we can conclude absolutely that there is, only one intellect—and not merely one intellect for all men. For if there is only one intellect, then, according to their argument, it follows that there is only one in the whole world, and not simply one for all men. Therefore our intellect is not only a separate substance, but also it is God Himself, and any plurality of separate substances is rendered impossible.

Moreover, if someone should reply that the intellect of one separate substance is not the same in species as the intellect of another separate substance, since the intellects differ specifically, he would merely involve himself in further error: for what is understood is related to the act of understanding and to intellect, as an object is related to act and potency. Now, the object does not receive any species from the act or from the potency, but rather the contrary is true. It must, therefore, be granted absolutely that the intellection of one thing—for example, of a stone—is but one, not only in all men, but even in all intellects.

It now remains to inquire what intellection is. If they say that what is understood is an immaterial species existing in the possible intellect, they unwittingly are going over to the doctrine of Plato, who taught that we cannot have any science of sensible things, but that true science is concerned only with separate form. Nor does it affect the matter whether we say that the science about a stone is possessed in regard to the separate form of a stone, or concerning a form of the stone in the intellect. In each case it follows that science is not concerned with things that are here, but with separate beings only. But because Plato held that immaterial forms of this sort were per se subsistent, he was able also to suppose that many intellects participated in the knowledge of one truth from one separate form. Those, however, who maintain that there are immaterial forms of this sort, which they say are understood, must hold that there is only one intellect, not only for all men, but one absolutely.

Therefore it must be said, according to the opinion of Aristotle, that what is understood, which is one, is the nature itself or the quiddity of the thing. For natural science and the other sciences are of things, not of intelligible species. Now, if what is understood were not the very nature of the stone (which nature is in things), but were the species in the intellect, it would follow that I would not know the thing—that is, the stone—but only the idea abstracted from the stone. But it is also true that the nature of the stone, in so far as it is singular, is potentially intelligible, but becomes actually intelligible by this, that, through the mediation of the senses, the species from sensible things come eventually to the phantasm, and that by the power of the active intellect the intelligible species are abstracted, which are then possessed in the possible intellect. These species, however, are not related to the possible intellect as the objects of its understanding, but as the species by which the intellect knows its object: just as also the species that are in the eye are not the things seen, but those things by which the eye sees—unless so far as the mind reflects upon itself: a thing that cannot occur in a sense faculty.

Furthermore, if understanding were an action passing over into exterior matter, as in the case of burning or moving it, it would follow that intellection would be according to the mode by which a nature really has its existence in singular things (as the action of fire is according to the mode of what is combustible). But because intellection is an action remaining in the person who understands, as Aristotle says in IX Metaph., it follows that understanding is according to the manner of the one knowing, that is, according to the exigency of the species by means of which the intellect understands. These intelligible species, however, since they are abstracted from their individuating principles, do not represent the thing according to any individual conditions, but only according to the universal nature of the thing. Now, if two qualities coexist in an object, nothing hinders one from being capable of representation, even in the senses, without the other; wherefore, the color of honey or of an apple may be seen by the eye without there being any experience of its taste. Thus the intellect understands the universal nature of things by abstracting from individuating principles.

One object, therefore, is understood by me and by you. But it is by means of one thing that it is so understood by me, and by means of another, by you; that is, by a different intelligible species. Thus my intellection is one thing, and yours is another. My intellect is one, and yours is another. Therefore Aristotle says in the Praedicamenta: Every science is individual in relation to its subject. Hence the grammar that a person possesses is said to be in his soul, but is not said to concern the whole person. From this fact, it results also that when my intellect knows that it understands, it knows a certain singular act; but when it understands intellection, absolutely, it knows something universal; for singularity is not repugnant to intelligibility, but materiality is. Therefore, since some singular things are immaterial, such as the separate substances previously discussed, nothing hinders such singulars from being intellected.

Hence it is also apparent how the same science can be in the pupil and in the teacher. The object known is the same, but not the intelligible species by which each understands. Accordingly knowledge in me and in another is individuated; nor is it necessary that the knowledge of a pupil should be caused by the knowledge of the teacher, as is the heat of water by the heat of fire; but as health, which is in matter, by the health which is in the mind of the physician. For just as in the sick man there is a natural principle of health, to which the physician ministers by his skill in order to establish perfect health, so in the pupil there is a natural principle of science, namely, the active intellect, and the first principles, which are intuitively known, per se nota. Moreover, the teacher furnishes certain aids by deducing conclusions from principles known in themselves; and, as the physician strives to produce health according to the manner in which nature heals (by making use of heat and cold), so the teacher develops science in that way by which the pupil may, through his own efforts, come to acquire knowledge: that is, by proceeding from the known to the unknown. And as health is restored to the infirm man, not because of the power of the physician, but because of a faculty of nature, so also knowledge is caused in a pupil, not as something owing to the power of the master, but according to a natural facility for learning.

But there are others who object further that, if many intellectual substances were to remain after the destruction of bodies, it would follow that they would be without any work to perform. So Aristotle in II Metaph. argued that, if there were separate substances that did not animate a body, they would have nothing to do. But if they had well considered this statement of Aristotle, they would have been able easily to solve this difficulty. For before introducing this idea, Aristotle had said previously: "Wherefore it is altogether reasonable to suppose that both these substances and immovable principles exist; but it is left to greater philosophers to declare that they necessarily do so." From this statement it is evident that he himself adhered to the idea that they were probable, and did not declare their necessary existence.

In the second place, since "to be without function or duty occurs when a being does not tend toward the end to which it is ordained, we could not say, even with probability, that the separated substances would be without function if they did not give motion to bodies, unless perhaps we might declare that the moving of bodies is the end for which separate substances exist. But this is quite impossible, since the end must be greater than the beings that are ordained to it. Therefore Aristotle does not say that separate substances would be useless if they did not move bodies, but he says that in his opinion "Every impassible substance, by reason of its very nature, should be assigned to an end supremely good. It is an indication of the greater perfection of anything that it is good not only in itself, but that it causes goodness in others. Consequently, since the way separate substances cause good in lesser beings had not been revealed except through the motion of certain bodies, Aristotle derived from this a probable reason to show that there are no other separate substances than those made known to us by the movement of the heavenly bodies. However, that he did not hold this theory to be necessarily true, he himself declares.

Moreover, we concede that the human soul, after being separated from the body, has not the ultimate perfection of its human nature, since it is a part of human nature. Now, no part is an altogether perfect thing if it has been separated from the whole. Not on this account, however, is the soul without any action; for the end of the human soul is not to animate a body, but to understand; and in this its felicity consists as Aristotle shows in X Ethic.

Still others add a further objection to their assertion of error, saying that if there were as many intellects as there are men it would follow that there would actually be an infinite number, according to the position of Aristotle, who held that the world was eternal and that men had always existed. To this objection, however, Algazel makes answer in his Metaphysics. For he says: "In the case of whatever one of things shall have existed without the other, such as quantity or multitude without order, infinity will not be rendered impossible; even as it is not impossible in the motion of heaven." And later he adds: "Likewise the souls of men, which are separable from bodies at death, we concede to be infinite in number even though they have their existence simultaneously, inasmuch as there is among them no ordination of nature by reason of which some souls should cease to be, since none of them is the cause of the others, but they are altogether equal in nature and in rank, with no priority or posteriority. Now this priority and posteriority are not to be understood as referring to their creation according to time. However, in regard to their essential character, inasmuch as they are essences, there is no order of priority, but they are equal in existence; though they are not as regards time and bodies, and cause and effect."

How Aristotle would have solved this problem, we cannot tell because we do not possess that part of his Metaphysics in which he discussed separate substances. But the Philosopher does say in II Physic. The consideration of forms which are separate or of those which, although they are in matter, are separable from it, is the task of first philosophy. However, no matter what he may have said, evidently on this point Catholics suffer no perplexity; for they hold it [on faith] that the world did have a beginning.

The statement of our opponents, therefore, is evidently false: that it was a principle of all the philosophers, both Arabs and Peripatetics, that the intellect was not numerically multiplied, and that only among the Latin writers was this not held as true. Now, Algazel was not a Latin, but an Arabian. Avicenna also, who likewise was an Arabian, says in his book De anima: "Prudence and stupidity and opinion and other like things do not exist except in the essence of the soul." Hence there is not one soul, but there are numerically many souls; and their species is one.

Furthermore, in order not to omit mention of the Greeks, the words of Themistius regarding this problem are to be noted. In his commentary on the De anima, after he had inquired whether the active intellect were one or many, he proceeds to give his answer: "Can it be truly said that there is but one first intellect illuminating all others, but that there are many which, having received this illumination, subsequently enlighten many others? In the same way, although the sun is only one, the light which goes forth from the sun and is given out by it is, as it were, separated from it and scattered and thus is diffused and distributed in many diverse rays. On this account, Aristotle did not compare the intellect to the sun, but to light; whereas, Plato compared it to the sun." Hence it is evident from the words of Themistius that neither the active intellect of which Aristotle speaks is a single one enlightening all others, nor is that which is illuminated, the possible intellect, only one. But it is true that the principle of all illumination is one: namely, some separate substance: either God, according to Catholic philosophers, or the Ultimate Intellect, according to Avicenna. The unicity of this separate principle, moreover, Themistius proves by the fact that he who teaches and he who learns understand the same thing. This could not be unless there were the same principle of intellectual light for both. But it is true that Themistius afterward relates that certain philosophers had been in doubt whether the possible intellect were one.

He says no more about it, however, because it had not been his purpose to investigate the various opinions of philosophers, but to present the judgments of Aristotle, Plato, and Theophrastus. Therefore at the end he concludes: "But I have stated that to pronounce judgment on what the Philosopher says is a task requiring singular zeal and care. However, this work has had for its purpose to indicate what one can gather from the statements we have collected as to the opinion of Aristotle, of Theophrastus, and more especially, of Plato himself. For the rest, it must be the place and task of another to determine what ought to be believed about the soul. But what the opinion of Aristotle was, and what that of Theophrastus and of Plato, I think can easily be discovered from the quotations from their own books which we have presented and analyzed." Hence it is clear that Aristotle and Theophrastus and Plato himself did not hold it as a principle that the possible intellect is one for all men. It is also evident that Averroes incorrectly presented the opinion of Themistius and of Theophrastus concerning both the possible and the active intellect. Therefore we have rightly called him the perverter of Peripatetic philosophy. Hence it is amazing that certain men, after seeing only the Commentary of Averroes, presume to declare, on his authority, that all the philosophers—Greeks and Arabians, excepting only the Latins—hold this opinion as certain.

However, it is a matter of much greater amazement, or rather even of indignation, that one who professes to be a Christian dares to speak so irreverently in regard to Christian faith. This he does when he says that the Latins do not accept this doctrine among their principles (namely, that there is but one intellect) because perhaps the law of their faith is in contradiction to it. Now, in this there are two evils:

first, because he doubts whether this teaching is against faith;

secondly, because he implies that he himself is estranged from or outside this law, and because he afterward says: "This is the reason why Catholics seem to hold this opinion." Here he calls an article of faith only an "opinion." Nor is it the less presumptuous that later he dares to assert that God could not create many intellects because this implies a contradiction.

However, what he subsequently declares is even more reprehensible: "By reason I conclude of necessity that the intellect is numerically one; nevertheless I firmly hold to the opposite by faith." Therefore he judges that faith is concerned with doctrines the contrary of which can be concluded "of necessity." Since, however, what I conclude of necessity can be only what is necessarily true,—the opposite of which is false and impossible—it follows that faith must be demanded in what is false and impossible: a thing that not even God could do. But the ears of men who have faith cannot endure such words. In his great temerity, moreover, he has not hesitated to dispute about questions that not only do not pertain to philosophy, but that are matters of pure faith: for example, that the soul suffers from the fire of hell, and that the judgment of the doctors on this point should be put aside. With equal reason one might enter into philosophical disputation about the Trinity or the Incarnation and other like questions, concerning which none but a babbler would speak.

These, therefore, are the assembled arguments that we have written in refutation of the aforesaid error, not arguments amassed by reference to the doctrines of faith, but collected from the reasons and words of the philosophers themselves. If any one, however, boastfully claiming a pseudo-science, wishes to say anything in contradiction to what we have written, let him not do his talking in out-of-the-way corners, or before mere boys who know not how to judge of difficult problems. But, if he dares, let him write an answer to what has been here written. He will find not me alone, who am the least, but many others who know and foster the truth, by whom his error may be refuted or his ignorance enlightened.