Continued in: Next
essence. Now it is impossible for anything which is not a pure act, but which has some admixture of potentiality, to be its own actuality: because actuality is opposed to potentiality. But God alone is pure act. Hence only in God is His substance the same as His existence and His action.
Besides, if an angel's act of understanding were his substance, it would be necessary for it to be subsisting. Now a subsisting act of intelligence can be but one; just as an abstract thing that subsists. Consequently an angel's substance would neither be distinguished from God's substance, which is His very act of understanding subsisting in itself, nor from the substance of another angel.
Also, if the angel were his own act of understanding, there could then be no degrees of understanding more or less perfectly; for this comes about through the diverse participation of the act of understanding.
Reply Obj. 1: When the active intellect is said to be its own action, such predication is not essential, but concomitant, because, since its very nature consists in act, instantly, so far as lies in itself, action accompanies it: which cannot be said of the passive intellect, for this has no actions until after it has been reduced to act.
Reply Obj. 2: The relation between "life" and "to live" is not the same as that between "essence" and "to be"; but rather as that between "a race" and "to run," one of which signifies the act in the abstract, and the other in the concrete. Hence it does not follow, if "to live" is "to be," that "life" is "essence." Although life is sometimes put for the essence, as Augustine says (De Trin. x), "Memory and understanding and will are one essence, one life": yet it is not taken in this sense by the Philosopher, when he says that "the act of the intellect is life."
Reply Obj. 3: The action which is transient, passing to some extrinsic object, is really a medium between the agent and the subject receiving the