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being, whom we call God; and that this first being must be pure act, without the admixture of any potentiality, for the reason that, absolutely, potentiality is posterior to act. Now everything which is in any way changed, is in some way in potentiality. Hence it is evident that it is impossible for God to be in any way changeable. Secondly, because everything which is moved, remains as it was in part, and passes away in part; as what is moved from whiteness to blackness, remains the same as to substance; thus in everything which is moved, there is some kind of composition to be found. But it has been shown above (Q. 3, A. 7) that in God there is no composition, for He is altogether simple. Hence it is manifest that God cannot be moved. Thirdly, because everything which is moved acquires something by its movement, and attains to what it had not attained previously. But since God is infinite, comprehending in Himself all the plenitude of perfection of all being, He cannot acquire anything new, nor extend Himself to anything whereto He was not extended previously. Hence movement in no way belongs to Him. So, some of the ancients, constrained, as it were, by the truth, decided that the first principle was immovable.
Reply Obj. 1: Augustine there speaks in a similar way to Plato, who said that the first mover moves Himself; calling every operation a movement, even as the acts of understanding, and willing, and loving, are called movements. Therefore because God understands and loves Himself, in that respect they said that God moves Himself, not, however, as movement and change belong to a thing existing in potentiality, as we now speak of change and movement.
Reply Obj. 2: Wisdom is called mobile by way of similitude, according as it diffuses its likeness even to the outermost of things; for nothing can exist which does not proceed from the divine wisdom by way of some kind of