the universal. For as
every action is according to the mode of the form by which the agent
acts, as heating is according to the mode of the heat; so knowledge
is according to the mode of the species by which the knower knows.
Now it is clear that common nature becomes distinct and multiplied by
reason of the individuating principles which come from the matter.
Therefore if the form, which is the means of knowledge, is
material--that is, not abstracted from material conditions--its
likeness to the nature of a species or genus will be according to the
distinction and multiplication of that nature by means of
individuating principles; so that knowledge of the nature of a thing
in general will be impossible. But if the species be abstracted from
the conditions of individual matter, there will be a likeness of the
nature without those things which make it distinct and multiplied;
thus there will be knowledge of the universal. Nor does it matter,
as to this particular point, whether there be one intellect or many;
because, even if there were but one, it would necessarily be an
individual intellect, and the species whereby it understands, an
individual species.

Reply Obj. 4: Whether the intellect be one or many, what is
understood is one; for what is understood is in the intellect, not
according to its own nature, but according to its likeness; for "the
stone is not in the soul, but its likeness is," as is said, _De
Anima_ iii, 8. Yet it is the stone which is understood, not the
likeness of the stone; except by a reflection of the intellect on
itself: otherwise, the objects of sciences would not be things, but
only intelligible species. Now it happens that different things,
according to different forms, are likened to the same thing. And
since knowledge is begotten according to the assimilation of the
knower to the thing known, it follows that the same thing may happen
to be known by several knowers; as is apparent in regard to the
senses; for several see the same color, according to different
likenesses. In the same way several intellects understand one object
understood. But there is this difference, according to the opinion of
Aristotle, between the sense and the intelligence--that a thing is
perceived by the sense according to the disposition which it has
outside the soul--that is, in its individuality; whereas the nature
of the thing understood is indeed outside the soul, but the mode
according to which it exists outs