We’re back into territory were the last of the travelers have disappeared. There are two successive Chapters which deal with the question below. I have selected only the highlights from both.
Chapter 74 Concerning the theory of Avicenna, who said that intelligible forms are not preserved in the possible intellect (alternate translation) We’re still using the alternate translation this week.
1 What Avicenna has to say, however, seems to conflict with the arguments given above, for he asserts in his De animal that the intelligible species do not remain in the possible intellect except when they are being actually understood.
Notes Avicenna was a Muslim philosopher-theologian at the turn of the first millennium.
2 Avicenna endeavors to prove this by arguing that, as long as the apprehended forms remain in the apprehending power, they are actually apprehended, since [as Aristotle says] “sense is actualized by being identified with the thing actually sensed” and, similarly, “the intellect in act is one with the thing actually understood” [De anima III, 2].
So, it seems that whenever sense or intellect becomes one with the thing sensed or understood, as the result of possessing its form, there is actual apprehension through sense or intellect. And Avicenna says that the powers wherein are preserved the forms not actually apprehended are not powers of apprehension, but store-houses thereof; for example, the imagination, which is the store-house of sense-apprehended forms, and the memory, which, he says, is the store-house of intentions apprehended without the senses—the sheep’s apprehension of the wolf as its enemy, for instance.
Now, it happens that these powers preserve forms not actually apprehended, so far as they possess bodily organs wherein forms are received in a manner closely resembling apprehension. Accordingly, the apprehensive power, by turning to these store-houses, apprehends actually. Now, the possible intellect certainly is an apprehensive power, and certainly it has no corporeal organ.
Hence, Avicenna concludes that it is impossible for the intelligible species to be preserved in the possible intellect, except while it understands actually.
There are, then, the following alternatives: either the intelligible species themselves must be preserved in some bodily organ or in some power having such an organ; or the intelligible forms are of necessity self-existent, our possible intellect being to them as a mirror to the things seen in it; or the intelligible species have to be infused anew into the possible intellect whenever it understands actually.
Now, the first of these three is impossible, because forms existing in powers which employ bodily organs are only potentially intelligible; and the second is the opinion of Plato, which Aristotle refutes in the Metaphysics [I, 9]. So, Avicenna takes the third, namely, that whenever we understand actually, the agent intellect, which he says is a separate substance, infuses intelligible species into our possible intellect…
5 But, if this position is examined carefully, it will be seen that in principle it differs little or not at all from that of Plato. For Plato maintained that intelligible forms are separate substances, from which knowledge poured into our souls, while Avicenna asserts that knowledge flows into our souls from one separate substance, the agent intellect. Now, so far as the manner of acquiring knowledge is concerned, it makes no difference whether it be caused by one or several separate substances; in either case, it follows that our knowledge is not caused by sensible things—a consequence clearly contradicted by the fact that a person who lacks one sense lacks, also, the knowledge of those sensible things which are known through that sense…
17 Now, the memory is located in the sensitive part of the soul, because its scope is limited to things subject to determinate times; there is memory only of what is past. Therefore, since memory does not abstract from singular conditions, it does not belong to the intellective part of the soul, which is cognizant of universals. This, however, does not stand in the way of the possible intellect’s retentiveness of intelligibles, which abstract from all particular conditions.
1 We must now show the inefficacy of the arguments put forward with the object of proving the unit of the possible intellect.
2 For it seems that every form which is one specifically and many in number is individuated by matter; because things one in species and many in number agree in form and differ in matter.
Therefore, if the possible intellect is multiplied numerically in different men, while being specifically one, then it must be individuated in this and that man by matter. But this individuation is not brought about by matter which is a part of the intellect itself, since in that case the intellect’s receptivity would be of the same genus as that of prime matter, and it would receive individual forms; which is contrary to the nature of intellect.
It remains that the intellect is individuated by that matter which is the human body and of which the intellect is held to be the form. But every form individuated by matter of which that form is the act is a material form. For the being of a thing must stem from that to which it owes its individuation; since just as common principles belong to the essence of the species, so individuating principles belong to the essence of this individual thing. It therefore follows that the possible intellect is a material form, and, consequently, that it neither receives anything nor operates without a bodily organ. And this, too, is contrary to the nature of the possible intellect. Therefore, the possible intellect is not multiplied in different men, but is one for them all…
Notes Don’t forget that the intellect is not a body.
6 As to the first argument adduced above, we admit that the possible intellect is specifically one in different men and yet is numerically many; though this is not to be taken so as to emphasize the fact that man’s parts are not ascribed to his generic or specific essence as such, but only as principles of the whole man. Nor does it follow that the possible intellect is a material form dependent on the body for its being. For just as it belongs to the human soul by its specific nature to be united to a particular species of body, so this particular soul differs only numerically from that one as the result of having a relationship to a numerically different body. In this way are human souls individuated in relation to bodies, and not as though their individuation were caused by bodies; and so the possible intellect, which is a power of the soul, is individuated likewise.
7 Averroes’ second argument fails because it does not distinguish between that by which one understands and that which is understood. The species received into the possible intellect is not that which is understood; for, since all arts and sciences have to do with things understood, it would follow that all sciences are about species existing in the possible intellect. And this is patently false, because no science, except logic and metaphysics, is concerned with such things.
And yet, in all the sciences, whatever is known is known through those species. Consequently, in the act of understanding, the intelligible species received into the possible intellect functions as the thing by which one understands, and not as that which is understood, even as the species of color in the eye is not that which is seen, but that by which we see. And that which is understood is the very intelligible essence of things existing outside the soul, just as things outside the soul are seen by corporeal sight. For arts and sciences were discovered for the purpose of knowing things as existing in their own natures.
8 Nor need we follow Plato in holding that, because science is about universals, universals are self-subsisting entities outside the soul.
For, although the truth of knowledge requires the correspondence of cognition to thing, this does not mean that these two must have the same mode of being.
For things united in reality are sometimes known separately; in a thing that is at once white and sweet, sight knows only the whiteness, taste only the sweetness. So, too, the intellect understands, apart from sensible matter, a line existing in sensible matter, although it can also understand it with sensible matter.
Now, this diversity comes about as a result of the diversity of intelligible species received into the intellect, the species being sometimes a likeness of quantity alone, and sometimes a likeness of a quantitative sensible substance. Similarly, although the generic nature and the specific nature never exist except in individual things, the intellect nevertheless understands those natures without understanding the individuating principles; and to do this is to understand universals.
Thus, there is no incompatibility between the fact that universals do not subsist outside the soul, and that in understanding universals the intellect understands things that do exist outside the soul. The intellect’s understanding of the generic or specific nature apart from the individuating principles is due to the condition of the intelligible species received into it, for the species is immaterialized by the agent intellect through being abstracted from matter and material conditions whereby a particular thing is individuated. Consequently, the sensitive powers are unable to know universals; they cannot receive an immaterial form, since whatever is received by them is always received in a corporeal organ…
Notes Plato (of all places) at Stanford has a decent article (thought it lapses into jargon too readily) on Aristotle and universals.
14 As to the third argument, its solution emerges from what has already been said. For Averroes statement that knowledge in the disciple and in the master is numerically one is partly true and partly false.
It is numerically one as concerns the thing known; it is not numerically one either in respect of the intelligible species whereby the thing is known, or of the habit of knowledge itself. Nor does this entail the consequence that the master causes knowledge in the disciple in the same way as fire generates fire.
For things are not in the same fashion generated by nature as by art; fire generates fire naturally, by making actual the form of fire potentially present in the matter, whereas the master causes knowledge in his disciple by way of art, since this is the aim of the art of demonstration, which Aristotle teaches in the Posterior Analytics; for demonstration is “a syllogism productive of scientific knowledge,” as he says in that work [I, 2].
Notes It may be better said that master tries to cause knowledge to flow into the student. He is not always successful; but when he is, it works like the next paragraph proves.
15 It must be borne in mind, however, that according to Aristotle’s teaching in Metaphysics VII  there are some arts wherein the matter is not an active principle productive of the art’s effect.
The art of building is a case in point, since in wood and stone there is no active force tending to the construction of a house, but only a passive aptitude.
On the other hand, there exists an art whose matter is an active principle tending to produce the effect of that art. Such is the art of medicine, for in the sick body there is an active principle conducive to health.
Thus, the effect of an art of the first kind is never produced by nature, but is always the result of the art; every house is an artifact. But the effect of an art of the second kind is the result both of art and of nature without art, for many are healed by the action of nature without the art of medicine.
Now, in those things that can be done both by art and by nature, art imitates nature; if the cause of a person’s illness is something cold, nature cures him by heating; and that is why the physician, if his services are needed in order to cure the patient, does so by applying heat.
Now, the art of teaching resembles this art. For in the person taught there is an active principle conducive to knowledge, namely, the intellect, and there are also those things that are naturally understood, namely, first principles. Knowledge, then, is acquired in two ways: by discovery without teaching, and by teaching.
So, the teacher begins to teach in the same way as the discoverer begins to discover, that is, by offering to the disciple’s consideration principles known by him, since all learning results from pre-existent knowledge; by drawing conclusions from those principles; and by proposing sensible examples, from which the phantasms necessary for the disciple’s understanding are found in the soul.
And since the outward action of the teacher would have no effect without the inward principle of knowledge, whose presence in us we owe to God, the theologians remark that man teaches by outward ministration, but God by inward operation. So, too, is the physician said to minister to nature in the practice of his art of healing. Thus, knowledge is caused in the disciple by his master, not by way of natural action, but of art, as was said…