herefore
neither would His being be perfect; and this is against what was said
above (Q. 4, A. 1). We must therefore hold that God knows things
other than Himself with a proper knowledge; not only in so far as
being is common to them, but in so far as one is distinguished from
the other. In proof thereof we may observe that some wishing to show
that God knows many things by one, bring forward some examples, as,
for instance, that if the centre knew itself, it would know all lines
that proceed from the centre; or if light knew itself, it would know
all colors.

Now these examples although they are similar in part, namely, as
regards universal causality, nevertheless they fail in this respect,
that multitude and diversity are caused by the one universal
principle, not as regards that which is the principle of distinction,
but only as regards that in which they communicate. For the diversity
of colors is not caused by the light only, but by the different
disposition of the diaphanous medium which receives it; and likewise,
the diversity of the lines is caused by their different position.
Hence it is that this kind of diversity and multitude cannot be known
in its principle by proper knowledge, but only in a general way. In
God, however, it is otherwise. For it was shown above (Q. 4, A. 2)
that whatever perfection exists in any creature, wholly pre-exists and
is contained in God in an excelling manner. Now not only what is
common to creatures--viz. being--belongs to their perfection, but
also what makes them distinguished from each other; as living and
understanding, and the like, whereby living beings are distinguished
from the non-living, and the intelligent from the non-intelligent.
Likewise every form whereby each thing is constituted in its own
species, is a perfection; and thus all things pre-exist in God, not
only as regards what is common to all, but also as regards what
distinguishes one thing from another. And therefore as God contains
all perfections in Himself, the essence of God is compared to all
other essences of things, not as the common to the proper, as unity is
to numbers, or as the centre (of a circle) to the (radiating) lines;
but as perfect acts to imperfect; as if I were to compare man to
animal; or six, a perfect number, to the imperfect numbers contained
under it. Now it is manifest that by a perfect act imperfect acts can
be known not only in general, but also by proper knowledge; thus, for
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