Chapter 31 — That God is his own act of understanding

God must also be his own act of understanding. Since ‘to understand’ is second act (as, for example ‘to consider’), whereas the corresponding first act is intellect or knowledge, any intellect that is not its own understanding is related to its understanding as potency to act. For in the order of potencies and acts, what is first is always potential with respect to what follows, and what is last is perfective. This is true only with reference to one and the same being, for among different beings the converse obtains; thus a mover and an agent are related to the thing moved and actuated as act to potency. In God, however, since he is pure act, there is nothing that is related to anything else as potency to act. Accordingly, God must be his own act of understanding.

Furthermore, the intellect is related to its act of understanding as essence is related to existence. But God understands through his essence, and his essence is his existence. Therefore, his intellect is his act of understanding. And thus the fact that God is intelligent implies no composition in him, since in him intellect and act of understanding and intelligible species are not distinct; and these in turn are nothing else than his essence.