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CHAPTER LXXVII: THAT IT IS NOT IMPOSSIBLE FOR THE POSSIBLE AND ACTIVE INTELLECT TO CONCUR IN THE ONE SUBSTANCE OF THE SOUL
PERHAPS it will seem impossible to someone that one and the same substance, namely, that of our soul, should be in potentiality to all intelligibles,--which belongs to the possible intellect,--and should make them actual,--which belongs to the active intellect: since a thing acts not as it is in potentiality, but as it is in act. Wherefore it does not appear how the active and possible intellect can concur in the one substance of the soul.
If, however, one look into the matter rightly, nothing impossible or difficult follows. For nothing hinders one thing from being in one respect in potentiality with regard to some other thing, and in act in another respect, as we observe in natural things: for air is actually damp and potentially dry, whereas with earth it is the other way about. Now we find this same comparison between the intellective soul and the phantasms. For the soul has something in act to which the phantasm is in potentiality, and is in potentiality to something which is found actually in the phantasms. Because the substance of the human soul has immateriality, and, as is evident from what has been said, it consequently has an intellectual nature, since such is every immaterial substance. Yet it does not follow that it is likened to this or that determinate thing, which is required in order that our soul may know this or that thing determinately: for all knowledge results from the likeness of the known in the knower. Hence the intellective soul remains itself in potentiality to the determinate likenesses of things that can be known by us, and these are the natures of sensible things. It is the phantasms that offer us these determinate natures of sensible things: which phantasms, however, have not yet acquired intelligible being,--since they are images of sensible things even as to material conditions, which are the individual properties,--and moreover are in material organs. Wherefore they are not actually intelligible. And yet, since in the individual man whose image the phantasms reflect it is possible to conceive the universal nature apart from all the individualizing conditions, they are intelligible potentially. Accordingly they have intelligibility potentially, though they are actually determinate as images of things: whereas it was the other way about in the intellective soul. Consequently there is in the intellective soul an active power in respect of the phantasms, rendering them actually intelligible, and this power of the soul is called the active intellect. There is also in the soul a power that is in potentiality to the determinate images of sensible things; and this is the power of the possible intellect.
Nevertheless that which is found in the soul differs from what is found in natural agents. Because in the latter one thing is in potentiality to something according to the same mode as it is actually found in another: for the matter of the air is in potentiality to the form of water in the same way as it is in water. Hence natural bodies which have a common matter are mutually active and passive in the same order. Whereas the intellective soul is not in potentiality to the likenesses of things which are in the phantasms, according to the mode in which they are there, but according as these images are raised to something higher, by being abstracted from the individualizing conditions of matter, so that they become actually intelligible. Consequently the action of the active intellect on the phantasm precedes the reception by the possible intellect. Wherefore the pre-eminence of the action is ascribed, not to the phantasms but to the active intellect. For this reason Aristotle says that it is compared to the possible intellect as art to matter.
We should have a perfect example of this if the eye, besides being a diaphanous body and receptive of colours, had sufficient light to make colours actually visible; even as certain animals are said to throw sufficient light on objects by the light of their eyes, for which reason they see more by night and less by day, because their eyes are weak, since they are moved by a dim, and confused by a strong light. There is something like this in our intellect forasmuch as with regard to things most manifest it is as the eye of the owl with regard to the sun: so that the little intellectual light which is connatural to us is sufficient for our act of intelligence.
It is clear that the intellectual light connatural to our soul suffices to cause the action of the active intellect, if we consider why it is necessary to place an active intellect in the soul. For the soul was found to be in potentiality to intelligibles, as the senses to sensibles: since just as we do not always sense, so neither do we always understand. Now these intelligibles which the human intellective soul understands were asserted by Plato to be intelligible of themselves, namely ideas: wherefore it was unnecessary for him to admit an active intelligence in respect of intelligibles. But if this were true, it would follow that the more things are intelligible of themselves, the more would they be understood by us. Yet this is clearly false: because the nearer things are to our senses the more intelligible are they to us, though in themselves they are less intelligible. Consequently Aristotle was moved to assert that those things which are intelligible to us, are not certain things that are intelligibles in themselves, but that they are made intelligible from sensibles. Hence he had to place a power which would do this; and this is the active intellect. Wherefore the reason for placing the active intellect is that it may make intelligibles proportionate to us. Now this does not exceed the mode of the intellectual light connatural to us. Therefore nothing hinders us from ascribing the action of the active intellect to the light of our soul, and especially since Aristotle compares the active intellect to a light.
|Source: St. Thomas Aquinas, The Summa Contra Gentiles, trans. by The English Dominican Fathers from the latest Leonine Edition, Benzinger Brothers: New York, 1924.|