immaterial things, just as, on the contrary, angels know material
things through the immaterial.

But Plato, considering only the immateriality of the human intellect,
and not its being in a way united to the body, held that the objects
of the intellect are separate ideas; and that we understand not by
abstraction, but by participating things abstract, as stated above
(Q. 84, A. 1).

Reply Obj. 1: Abstraction may occur in two ways: First, by way of
composition and division; thus we may understand that one thing does
not exist in some other, or that it is separate therefrom. Secondly,
by way of simple and absolute consideration; thus we understand one
thing without considering the other. Thus for the intellect to
abstract one from another things which are not really abstract from
one another, does, in the first mode of abstraction, imply falsehood.
But, in the second mode of abstraction, for the intellect to abstract
things which are not really abstract from one another, does not
involve falsehood, as clearly appears in the case of the senses. For
if we understood or said that color is not in a colored body, or that
it is separate from it, there would be error in this opinion or
assertion. But if we consider color and its properties, without
reference to the apple which is colored; or if we express in word
what we thus understand, there is no error in such an opinion or
assertion, because an apple is not essential to color, and therefore
color can be understood independently of the apple. Likewise, the
things which belong to the species of a material thing, such as a
stone, or a man, or a horse, can be thought of apart from the
individualizing principles which do not belong to the notion of the
species. This is what we mean by abstracting the universal from the
particular, or the intelligible species from the phantasm; that is,
by considering the nature of the species apart from its individual
qualities represented by the phantasms. If, therefore, the intellect
is said to be false when it understands a thing otherwise than as it
is, that is so, if the word "otherwise" refers to the thing
understood; for the intellect is false when it understands a thing
otherwise than as it is; and so the intellect would be false if it
abstracted the species of a stone from its matter in such a way as to
regard the species as not existing in matter, as Plato held. But it
is not so, if the word "otherwise" be taken as referring to the