Although even the letter of the old translation might be
kept in this respect, that the angels do not know their own power
perfectly; according as it proceeds from the order of the Divine
Wisdom, Which to the angels is incomprehensible.

Reply Obj. 2: We have no knowledge of single corporeal things, not
because of their particularity, but on account of the matter, which
is their principle of individuation. Accordingly, if there be any
single things subsisting without matter, as the angels are, there is
nothing to prevent them from being actually intelligible.

Reply Obj. 3: It belongs to the intellect, in so far as it is in
potentiality, to be moved and to be passive. Hence this does not
happen in the angelic intellect, especially as regards the fact that
he understands himself. Besides the action of the intellect is not of
the same nature as the action found in corporeal things, which passes
into some other matter.
_______________________

SECOND ARTICLE [I, Q. 56, Art. 2]

Whether One Angel Knows Another?

Objection 1: It would seem that one angel does not know another. For
the Philosopher says (De Anima iii, text. 4), that if the human
intellect were to have in itself any one of the sensible things, then
such a nature existing within it would prevent it from apprehending
external things; as likewise, if the pupil of the eye were colored
with some particular color, it could not see every color. But as the
human intellect is disposed for understanding corporeal things, so is
the angelic mind for understanding immaterial things. Therefore, since
the angelic intellect has within itself some one determinate nature
from the number of such natures, it would seem that it cannot
understand other natures.

Obj. 2: Further, it is stated in _De Causis_ that "every intelligence
knows what is above it, in so far as it is caused by it; and what is
beneath it, in so far as it is its cause." But one angel is not the
cause of another. Therefore one angel does not know another.

Obj. 3: Further, one angel cannot be known to another angel by the
essence of the one knowing; because all knowledge is effected by way
of a likeness. But the essence of the angel knowing is not like the
essence of the angel known, except generically; as is clear from what
has been said before (Q. 50, A. 4; Q. 55, A. 1, ad 3). Hence, it
follows that one angel would not have a particular knowledge of
another, but only a general knowledge. In like manne