THE INTELLECT IN GENERAL
AS TO THE PART OF THE SOUL BY WHICH IT KNOWS and is wise (whether separate spatially or only in idea) we must consider how it is differentiated and, further, how the operation of understanding arises.§§ 671-4
For if understanding is like sensing, it will be some kind of reception from an intelligible object, or some thing of that nature. It must then be impassible and yet receptive of a species, which it must already be potentially but not actually: and as the sense faculty stands to the sense-object, so will the intellective to the intelligible.§§ 675-6
It is also necessary, since its understanding extends to everything, that, as Anaxagoras says, it be uncompounded with anything so that it may command, i.e. know. For what appeared inwardly would prevent and impede what was without. Hence it has no nature and is not one, except in being potential. What then is called the 'intellect' of the soul (I mean that mind by which the soul forms opinions and understands) is not, before it understands, in act of any reality.§§ 677-83
Hence, it is a reasonable inference that it is not involved in the body. Were it so, it would also have some quality either hot or cold, and it would have an organ, like the sensitive faculties; but there is in fact none such.§§ 684-5
And they spoke to the point who said that the soul was the place of forms--yet not the whole soul, but the intellectual part; nor actually, but only potentially, is it any form.§ 686
That the impassibility of the sensitive faculty is not like that of the intellective faculty, is evident from the organs and from sensation itself. For the sense cannot receive an impression from too violent a sense-object--e.g. a sound from very great sounds, whilst from over-powerful odours there comes no smell, nor from over-strong colour any seeing. But when the intellect understands something highly intelligible, it does not understand what is inferior to these less than before, but more so. For whereas the sensitive faculty is not found apart from the body, the intellect is separate.§§ 687-99