I answer that, As the Philosopher states (De Anima iii, text. 8; Phys. viii, 32), the intellect is in potentiality in two ways; first, "as before learning or discovering," that is, before it has the habit of knowledge; secondly, as "when it possesses the habit of knowledge, but does not actually consider." In the first way an angel's intellect is never in potentiality with regard to the things to which his natural knowledge extends. For, as the higher, namely, the heavenly, bodies have no potentiality to existence, which is not fully actuated, in the same way the heavenly intellects, the angels, have no intelligible potentiality which is not fully completed by connatural intelligible species. But with regard to things divinely revealed to them, there is nothing to hinder them from being in potentiality: because even the heavenly bodies are at times in potentiality to being enlightened by the sun.
In the second way an angel's intellect can be in potentiality with regard to things learnt by natural knowledge; for he is not always actually considering everything that he knows by natural knowledge. But as to the knowledge of the Word, and of the things he beholds in the Word, he is never in this way in potentiality; because he is always actually beholding the Word, and the things he sees in the Word. For the bliss of the angels consists in such vision; and beatitude does not consist in habit, but in act, as the Philosopher says (Ethic. i, 8).
Reply Obj. 1: Movement is taken there not as the act of something imperfect, that is, of something existing in potentiality, but as the act of something perfect, that is, of one actually existing. In this way understanding and feeling are termed movements, as stated in De Anima iii, text. 28.
Reply Obj. 2: Such desire on the part of the angels does not exclude the object desired, but weariness thereof. Or they are said to desire the vision of God with regard to fresh revelations, which they receive from God to fit them for the tasks which they have to perform.
Reply Obj. 3: In the angel's substance there is no potentiality divested of act. In the same way, the angel's intellect is never so in potentiality as to be without act. _______________________
SECOND ARTICLE [I, Q. 58, Art. 2]
Whether an Angel Can Understand Many Things at the Same Time?
Objection 1: It would seem that an angel cannot understand many things at the same time. For the Philosopher says (Topic. ii, 4) that "it may happen that we know many things, but understand only one."
Obj. 2: Further, nothing is understood unless the intellect be informed by an intelligible species; just at the body is formed by shape. But one body cannot be formed into many shapes. Therefore neither can one intellect simultaneously understand various intelligible things.
Obj. 3: Further, to understand is a kind of movement. But no movement terminates in various terms. Therefore many things cannot be understood altogether.