20. We may thus distinguish two phases of Intellect, in one of which it may be taken as having no contact whatever with particulars and no Act upon anything; thus it is kept apart from being a particular intellect. In the same way science is prior to any of its constituent species, and the specific science is prior to any of its component parts: being none of its particulars, it is the potentiality of all; each particular, on the other hand, is actually itself, but potentially the sum of all the particulars: and as with the specific science, so with science as a whole. The specific sciences lie in potentiality in science the total; even in their specific character they are potentially the whole; they have the whole predicated of them and not merely a part of the whole. At the same time, science must exist as a thing in itself, unharmed by its divisions.
So with Intellect. Intellect as a whole must be thought of as prior to the intellects actualized as individuals; but when we come to the particular intellects, we find that what subsists in the particulars must be maintained from the totality. The Intellect subsisting in the totality is a provider for the particular intellects, is the potentiality of them: it involves them as members of its universality, while they in turn involve the universal Intellect in their particularity, just as the particular science involves science the total.
The great Intellect, we maintain, exists in itself and the particular intellects in themselves; yet the particulars are embraced in the whole, and the whole in the particulars. The particular intellects exist by themselves and in another, the universal by itself and in those. All the particulars exist potentially in that self-existent universal, which actually is the totality, potentially each isolated member: on the other hand, each particular is actually what it is [its individual self], potentially the totality. In so far as what is predicated of them is their essence, they are actually what is predicated of them; but where the predicate is a genus, they are that only potentially. On the other hand, the universal in so far as it is a genus is the potentiality of all its subordinate species, though none of them in actuality; all are latent in it, but because its essential nature exists in actuality before the existence of the species, it does not submit to be itself particularized. If then the particulars are to exist in actuality- to exist, for example, as species- the cause must lie in the Act radiating from the universal.