Whether an angel's act of understanding is his substance?

❌ Objection 1 : It would seem that the angel's act of understanding is his substance. For the angel is both higher and simpler than the active intellect of a soul. But the substance of the active intellect is its own action; as is evident from Aristotle (De Anima iii) and from his Commentator [*Averroes, A.D. 1126-1198]. Therefore much more is the angel's substance his action---that is, his act of understanding.

❌ Objection 2 : Further, the Philosopher says (Metaph. xii, text 39) that "the action of the intellect is life." But "since in living things to live is to be," as he says (De Anima ii, text 37), it seems that life is essence. Therefore the action of the intellect is the essence of an angel who understands.

❌ Objection 3 : Further, if the extremes be one, then the middle does not differ from them; because extreme is farther from extreme than the middle is. But in an angel the intellect and the object understood are the same, at least in so far as he understands his own essence. Therefore the act of understanding, which is between the intellect and the thing understood, is one with the substance of the angel who understands.