Need for an agent intellect

Aquinas on the need for agent intellect:

Aristotle chose a middle course. For with Plato he agreed that intellect and sense are different. But he held that the sense has not its proper operation without the cooperation of the body; so that to sense is not an act of the soul alone, but of the composite. ... But Aristotle held that the intellect has an operation in which the body does not share. Now nothing corporeal can make an impression on the incorporeal. And therefore, in order to cause the intellectual operation, according to Aristotle, the impression caused by sensible bodies does not suffice, but something more noble is required, for the agent is more noble than the patient, as he says. Not, be it observed, in the sense that the intellectual operation is effected in us by the mere impression of some superior beings, as Plato held; but that the higher and more noble agent which he calls the agent intellect, of which we have spoken above, causes the phantasms received from the senses to be actually intelligible, by a process of abstraction. (STh I.84.6 c. Pegis.)

Aquinas on Plato

Aquinas rejecting the principle that like is known by like (see De Smet):

Now it seems that Plato strayed from the truth because, having observed that all knowledge takes places through some kind of similitude, he thought that the form of the thing known must of necessity be in the knower in the same manner as in the thing known itself. But it was his opinion that the form of the thing understood is in the intellect under conditions of universality, immateriality, and immobility; which is apparent from the very operation of the intellect, whose act of understanding is universal, and characterized by a certain necessity; for the mode of action corresponds to the mode of the agent's form. Therefore he concluded that the things which we understand must subsist in themselves under the same conditions of immateriality and immobility.

 But there is no necessity for this. ... the sensible form is in one way in the thing whcih is external to the soul, and in another way in the senses, which receive the forms of sensible things without receiving matter.... So, too, the intellect, according to its own mode, receives under conditions of immateriality and immobility the species of material and movable bodies; for the received is in the receiver according to the mode of the receiver. We must conclude, therefore, that the soul knows bodies through the intellect by a knowledge which is immaterial, universal and necessary. (STh I.84.1 c. Basic Writings of Saint Thomas Aquinas. Vol. I. Ed. Anton C. Pegis. New York: Random House, 1945.)

See also STh I.84.2 c for more on why the principle that like is known by like is to be rejected. Here Aquinas concludes that the soul does not understand corporeal things by its essence; only God does.

God's knowledge of everything

Aquinas on how God knows everything by knowing himself:

Hence many ideas exist in the divine mind, as things understood by it; as can be proved thus. Inasmuch as He knows His own essence perfectly, He knows it according to every mode in which it can be known. (STh I.15.2 c. The "Summa Theologica" of St. Thomas Aquinas. Part I. QQ. I-XXVI. Literally translated by Fathers of the English Dominican Province. 2nd rev. ed. London: Burns Oates & Washbourne, 1920)

Aquinas on knowledge of sensible things

Augustine held that there is no communication from body to soul, but only from soul to body. Thomas Aquinas instead, in the De Veritate, has the following questions:
Does the mind know material things? (q. 10, a. 4)
Can our mind know material things in their singularity? (q. 10, a. 5)
Does the human mind receive knowledge from sensible things? (q. 10, a. 6)

Augustine's theory of divine illumination

In my effort to find texts in Augustine for my Philosophy of Knowing course, I had recourse to Gilson's study of Augustine. I find his treatment of Augustine's theory of divine illumination extremely interesting, though I must confess that I am merely skimming through it impatiently. Here are some excerpts:

... Augustine deliberately removes from divine illumination any knowledge which our intellect might abstract from the sensible and even denies that our intellect can have the sensible as its object. Only reason has dealings with the sensible; as for the intellect, it busies itself only with the intelligible order and has nothing to abstract from material things. The divine light it receives is not given it for that purpose. But, if illumination does not abstract, what does it do? [84. Clear distinction between reason and intellect. So, at least as far as Augustine is concerned, keep this very Platonic distinction in mind: reason deals with the sensible, intellect with the intelligible.]

Of this question we can say without exaggeration that it has tested the acumen of many generations of historians. The most obvious postulate for the problem is that there are no postulates. Augustine tells us neither how the intellect operates nor what it does. Some historians say simply that this is a serious lacuna; others, while admitting that Augustine said nothing of the sort, do their utmost to fill the lacuna by attributing to Augustine's thought an abstractive activity such as we have mentioned.... However, it seems to me that there is a simpler hypothesis to consider, namely that there is no lacuna here provided we look at things from Augustine's point of view and refuse to base our arguments on principles he did not accept. Actually, in Augustine there is no problem involving an Umsetzung (transformation) of the sensible into the intelligible. If he did not solve this problem, the reason was that he had no such problem to solve. If we insist that he solve it, then we do not fill a lacuna in his doctrine but change it into something else and in doing so take on ourselves the responsibility of foisting it on him. [84.]

Let us remember first of all that Augustine's interest lies not so much in the formation of a concept as in the formation of a knowledge of truth. In his teaching, everything happens as if there were no need to account for the general character of general ideas. Instead of finding fault with him for this or remedying this situation more or less arbitrarily, we might do well to see why he was not struck by the importance of the problem. 

Augustine thinks of the universe as matter in which the divine ideas / have implanted the intelligible.... Strictly speaking, the universe is intelligible to a mind that is capable of knowing it as such. Now it is very true that the world of things, by reason of its corporeity, cannot enter the mind, which is hierarchically superior to it, and for this reason abstraction properly so called is impossible in such a doctrine.There is no communication between substances in the direction of body to soul, but owing to the superiority of the soul over the body, there can be communication between substances in the direction of soul to body.... Because of this, the Augustinian soul can decipher directly, in the numbers of the changes undergone by its body, the numbers of the exterior bodies which produce these changes.... In order to have Aristotelian abstraction in Augustinism, we should have to find a place for the action of body on soul, and there is no place for it. In order to have in Augustinism a vision in God such as Malebranche proposed, we should have to do away with its direct communication of soul with body, and this is a power which Augustine always accorded the soul by reason of its transcendence alone. Between these two opposing conceptions, Augustinism remains what it was: a doctrine in which mind can read the intelligible directly in the image and consequently need do nothing more than discover where the source of truth is to be found. [84-5.]

As an historian, and he could be a good one, Saint Thomas saw clearly that, if we introduce an agent intellect into Plato's universe, it cannot have the same functions there as it had in Aristotle's universe. in an Aristotelian world, an agent intellect is needed to effect the intelligible, and this is the task of abstraction. In a Platonic world, on the other hand, an agent intellect is not needed to produce intelligibles because the human intellect finds them ready-made in its images; it is needed only to bestow the intelligible light on the understanding subject. Illumination of the mind by God in Augustinism, in Aristotelianism illumination of the object by a mind which God illumines; here is the difference between illumination-truth and illumination-abstraction. [86.]

Thus it seems true to say - salve meliore judicio - that illumination as Augustine saw it has as its exact point of application not so much the power to conceive as the power to judge, because in his view the intelligibility of the concept resides rather in the normative character which its own necessity bestows on the concept than in the general character of its extension. [91.] 

Memory, experience, art

Aristotle, Metaphysics, Book I 980b 25 - 981a 6:

The animals other than man live by appearances and memories, and have but little of connected experience; but the human race lives also by art and reasonings. And from memory experience is produced in men; for many memories of the same thing produce finally the capacity for a single experience. Experience seems to be very similar to science and art, but really science and art come to men through experience; for "experience made art," as Polus says, "but inexperience luck." And art arises, when from many notions gained by experience one universal judgment about similar objects is produced.

The philomythos and the philosophos

Aristotle, Metaphysics Book I 982b 12-20:

For it is owing to their wonder that men both now begin and at first began to philosophize; ... And a man who is puzzled and wonders thinks himself ignorant (whence even the lover of myth is in a sense a lover of wisdom, for myth is composed of wonders)...