Two Chapters in one this week. More arguments from our good saint refuting arguments which are no longer in much play. Next week: Proof of the immortality of the soul!
1 Perhaps someone will think it impossible for one and the same substance, namely, that of our soul, to be in potentiality to all intelligibles, as becomes the possible intellect, and to actualize them, as becomes the agent intellect. For nothing acts so far as it is in potentiality, but so far as it is in act. That is why it will seem impossible for the agent and possible intellect to exist concurrently in the one substance of the soul.
2 Upon close examination, however, it is seen that this concurrence entails nothing incongruous or difficult. For nothing prevents one thing from being in one respect potential in relation to some other thing, and actual in another respect, as we observe in things of nature; air is actually damp and potentially dry, and the reverse is true of earth.
Now, this same interrelationship obtains between the intellective soul and the phantasms. For the intellective soul has something actual to which the phantasm is potential, and is potential to something present actually in the phantasm; since the substance of the human soul is possessed of immateriality, and, as is clear from what has been said, it therefore has an intellectual nature—every immaterial substance being of this kind.
But this does not mean that the soul is now likened to this or that determinate thing, as it must be in order to know this or that thing determinately; for all knowledge is brought about by the likeness of the thing known being present in the knower. Thus, the intellectual soul itself remains potential with respect to the determinate likenesses of things that can be known by us, namely, the natures of sensible things.
It is the phantasms which present these determinate sensible natures to us. But these phantasms have not yet acquired intelligible actuality, since they are likenesses of sensible things even as to material conditions, which are the individual properties, and, moreover, the phantasms exist in material organs. Consequently, they are not actually intelligible.
They are, however, potentially intelligible, since in the individual man whose likeness the phantasms reflect it is possible to receive the universal nature stripped of all individuating conditions. And so, the phantasms have intelligibility potentially, while being actually determinate as likenesses of things. In the intellective soul the opposite was the case. Hence, there is in that soul an active power vis-à-vis the phantasms, making them actually intelligible; and this power is called the agent intellect; while there is also in the soul a power that is in potentiality to the determinate likenesses of sensible things; and this power is the possible intellect.
3 That which exists in the soul, however, differs from what is found in natural agents. For in the latter, one thing is in potentiality to something according to the same manner of being as that of its actual presence in something else; the matter of air is in potentiality to the form of water in the same way as it is in water.
That is why natural bodies, which have matter in common, are mutually active and passive in the same order.
On the other hand, the intellective soul is not in potentiality to the likenesses of things in the phantasms, according to the mode of their presence therein, but according as they are raised to a higher level by abstraction from material individuating conditions, thus being made actually intelligible. The action of the agent intellect on the phantasm, therefore, precedes the reception by the possible intellect, so that operational primacy here is ascribed not to the phantasms, but to the agent intellect. And for this reason Aristotle says that the agent intellect is related to the possible intellect as art to its matter.
Notes It may help to think that nothing is static in the interface between passive and active intellect. There is constant turmoil.
4 A quite similar case would be that of the eye, if, being transparent and receptive of colors, it were endowed with sufficient light to make colors actually visible; even as certain animals are said to illuminate objects for themselves by the light of their own eyes, and so they see more at night and less by day, for their eyes are weak, being activated by a dim light and confused by a strong one. There is something comparable to this in our intellect, which, “as regards things which are most evident of all, is as the eyes of the owl to the blaze of day”; so that the little intelligible light which is connatural to us suffices for our act of understanding…
Notes I kept this for the word “connatural.”
1 Now, since a number of persons agree with the Avicennian theory dealt with above, in the belief that it is the position of Aristotle, we must show from his own words that in his judgment the agent intellect is not a separate substance.
2 For Aristotle says [De anima III, 5] that in “every nature we find two factors, the one material, which, like the matter in every genus, is in potentiality to all the things contained under it, the other causal, which, like the efficient cause, produces all the things of a given genus, the latter factor standing to the former as art to its matter”; and therefore, Aristotle concludes, “these two factors must likewise be found within the soul.”
The quasi-material principle in the soul is “the (possible) intellect wherein all things become intelligible”; the other principle, having the role of efficient cause in the soul, “is the intellect by which all things are made” (namely, actually intelligible), and this is the agent intellect, “which is like a habit,” and not a power.
Aristotle explains what he means by calling the agent intellect a habit, when he goes on to speak of it as a kind of light, for “in a certain way light makes potential colors to be colors actually,” that is to say, so far as it makes them actually visible. And this function in regard to intelligibles is attributed to the agent intellect…
Notes This is a key paragraph, so take your time with it. It no way depends on Aristotle’s different understand of color and light. This is backed up in paragraphs 4 and 6.
4 Aristotle’s reasoning also proves the same point. For in every nature containing potentiality and act we find something which, having the character of matter, is in potentiality to the things of that genus, and something in the role of an efficient cause which actualizes the potentiality; similarly, in the products of art there is art and matter.
But the intellective soul is a nature in which we find potentiality and act, since sometimes it is actually understanding, and sometimes potentially.
Consequently, in the nature of the intellective soul there is something having the character of matter, which is in potentiality to all intelligibles—and this is called the possible intellect; and there also is something which, in the capacity of an efficient cause, makes all in act—and this is called the agent intellect….
6 Yet, what this Aristotelian phrase means is not that the effect produced by the agent intellect may be called a habit, as though the sense were that the agent intellect makes man to understand all things, and this effect is like a habit.
“For the essence of habit,” as the Commentator, Averroes, says on this very text, “consists in this, that its possessor understands by means of that which is proper to him—understands by himself and whenever he wills, with no need of anything extrinsic”; since Averroes explicitly likens to a habit, not the effect itself, but “the intellect by which we make all things.”
Notes The remaining paragraphs I leave off, since most will be now convinced the active and passive intellects are together in one soul. If not, St Thomas has half dozen more observations to make.