at another non-existing, but exists always.

Obj. 3: Further, Augustine (De Trin. xiii) proves the soul's
incorruptibility by the fact that the mind is capable of truth. But as
truth is incorruptible, so is it eternal. Therefore the intellectual
nature of the soul and of the angel is not only incorruptible, but
likewise eternal.

_On the contrary,_ It is said (Prov. 8:22), in the person of begotten
Wisdom: "The Lord possessed me in the beginning of His ways, before He
made anything from the beginning." But, as was shown above (A. 1), the
angels were made by God. Therefore at one time the angels were not.

_I answer that,_ God alone, Father, Son and Holy Ghost, is from
eternity. Catholic Faith holds this without doubt; and everything to
the contrary must be rejected as heretical. For God so produced
creatures that He made them "from nothing"; that is, after they had
not been.

Reply Obj. 1: God's being is His will. So the fact that God produced
the angels and other creatures by His being does not exclude that He
made them also by His will. But, as was shown above (Q. 19, A. 3; Q.
46, A. 1), God's will does not act by necessity in producing
creatures. Therefore He produced such as He willed, and when He
willed.

Reply Obj. 2: An angel is above that time which is the measure of the
movement of the heavens; because he is above every movement of a
corporeal nature. Nevertheless he is not above time which is the
measure of the succession of his existence after his non-existence,
and which is also the measure of the succession which is in his
operations. Hence Augustine says (Gen. ad lit. viii, 20,21) that "God
moves the spiritual creature according to time."

Reply Obj. 3: Angels and intelligent souls are incorruptible by the
very fact of their having a nature whereby they are capable of truth.
But they did not possess this nature from eternity; it was bestowed
upon them when God Himself willed it. Consequently it does not follow
that the angels existed from eternity.
_______________________

THIRD ARTICLE [I, Q. 61, Art. 3]

Whether the Angels Were Created Before the Corporeal World?

Objection 1: It would seem that the angels were created before the
corporeal world. For Jerome says (In Ep. ad Tit. i, 2): "Six thousand
years of our time have not yet elapsed; yet how shall we measure the
time, how shall we count the ages, in which the Angels, Thrones,
Dominations, and the other orders served God?" Damascene also