ikeness contained in the sense, but because one
thing is made from both as from act and potentiality: so likewise the
intellect in act is said to be the thing understood in act, not that
the substance of the intellect is itself the similitude by which it
understands, but because that similitude is its form. Now, it is
precisely the same thing to say "in things which are without matter,
the intellect is the same thing as the object understood," as to say
that "the intellect in act is the thing understood in act"; for a
thing is actually understood, precisely because it is immaterial.

Reply Obj. 3: The things which are beneath the angel, and those which
are above him, are in a measure in his substance, not indeed
perfectly, nor according to their own proper formality--because the
angel's essence, as being finite, is distinguished by its own
formality from other things--but according to some common formality.
Yet all things are perfectly and according to their own formality in
God's essence, as in the first and universal operative power, from
which proceeds whatever is proper or common to anything. Therefore
God has a proper knowledge of all things by His own essence: and this
the angel has not, but only a common knowledge.
_______________________

SECOND ARTICLE [I, Q. 55, Art. 2]

Whether the Angels Understand by Species Drawn from Things?

Objection 1: It would seem that the angels understand by species drawn
from things. For everything understood is apprehended by some likeness
within him who understands it. But the likeness of the thing existing
in another is there either by way of an exemplar, so that the likeness
is the cause of the thing; or else by way of an image, so that it is
caused by such thing. All knowledge, then, of the person understanding
must either be the cause of the object understood, or else caused by
it. Now the angel's knowledge is not the cause of existing things;
that belongs to the Divine knowledge alone. Therefore it is necessary
for the species, by which the angelic mind understands, to be derived
from things.

Obj. 2: Further, the angelic light is stronger than the light of the
active intellect of the soul. But the light of the active intellect
abstracts intelligible species from phantasms. Therefore the light of
the angelic mind can also abstract species from sensible things. So
there is nothing to hinder us from saying that the angel understands
through species drawn from things.