of understanding.
But truth, being a certain equality between thought and thing, is not
subject to more or less; for a thing cannot be said to be more or
less equal. Therefore a thing cannot be more or less understood.

Obj. 3: Further, the intellect is the most formal of all that is in
man. But different forms cause different species. Therefore if one
man understands better than another, it would seem that they do not
belong to the same species.

_On the contrary,_ Experience shows that some understand more
profoundly than do others; as one who carries a conclusion to its
first principles and ultimate causes understands it better than the
one who reduces it only to its proximate causes.

_I answer that,_ A thing being understood more by one than by another
may be taken in two senses. First, so that the word "more" be taken as
determining the act of understanding as regards the thing understood;
and thus, one cannot understand the same thing more than another,
because to understand it otherwise than as it is, either better or
worse, would entail being deceived, and such a one would not
understand it, as Augustine argues (QQ. 83, qu. 32). In another sense
the word "more" can be taken as determining the act of understanding
on the part of him who understands; and so one may understand the same
thing better than someone else, through having a greater power of
understanding: just as a man may see a thing better with his bodily
sight, whose power is greater, and whose sight is more perfect. The
same applies to the intellect in two ways. First, as regards the
intellect itself, which is more perfect. For it is plain that the
better the disposition of a body, the better the soul allotted to it;
which clearly appears in things of different species: and the reason
thereof is that act and form are received into matter according to
matter's capacity: thus because some men have bodies of better
disposition, their souls have a greater power of understanding,
wherefore it is said (De Anima ii, 9), that "it is to be observed that
those who have soft flesh are of apt mind." Secondly, this occurs in
regard to the lower powers of which the intellect has need in its
operation: for those in whom the imaginative, cogitative, and
memorative powers are of better disposition, are better disposed to
understand.

The reply to the First Objection is clear from the above; likewise the
reply to the Second, for the truth of the intellect consis