, as may happen in two ways. For in some agents the form of the
thing to be made pre-exists according to its natural being, as in
those that act by their nature; as a man generates a man, or fire
generates fire. Whereas in other agents (the form of the thing to be
made pre-exists) according to intelligible being, as in those that
act by the intellect; and thus the likeness of a house pre-exists in
the mind of the builder. And this may be called the idea of the
house, since the builder intends to build his house like to the form
conceived in his mind. As then the world was not made by chance, but
by God acting by His intellect, as will appear later (Q. 46, A. 1),
there must exist in the divine mind a form to the likeness of which
the world was made. And in this the notion of an idea consists.

Reply Obj. 1: God does not understand things according to an idea
existing outside Himself. Thus Aristotle (Metaph. ix) rejects the
opinion of Plato, who held that ideas existed of themselves, and not
in the intellect.

Reply Obj. 2: Although God knows Himself and all else by His own
essence, yet His essence is the operative principle of all things,
except of Himself. It has therefore the nature of an idea with
respect to other things; though not with respect to Himself.

Reply Obj. 3: God is the similitude of all things according to His
essence; therefore an idea in God is identical with His essence.
_______________________

SECOND ARTICLE [I, Q. 15, Art. 2]

Whether Ideas Are Many?

Objection 1: It seems that ideas are not many. For an idea in God is
His essence. But God's essence is one only. Therefore there is only
one idea.

Obj. 2: Further, as the idea is the principle of knowing and
operating, so are art and wisdom. But in God there are not several
arts or wisdoms. Therefore in Him there is no plurality of ideas.

Obj. 3: Further, if it be said that ideas are multiplied according to
their relations to different creatures, it may be argued on the
contrary that the plurality of ideas is eternal. If, then, ideas are
many, but creatures temporal, then the temporal must be the cause of
the eternal.

Obj. 4: Further, these relations are either real in creatures only,
or in God also. If in creatures only, since creatures are not from
eternity, the plurality of ideas cannot be from eternity, if ideas
are multiplied only according to these relations. But if they are
real in God, it follows that there is a real plurality i