Chapter 53 — That in created intellectual substances there is act and potency

From the foregoing it is evident that in created intellectual substances, there is composition of act and potency.

For in whatever thing we find two of which one is the complement of the other, the proportion of one of them to the other is as the proportion of potency to act, since nothing is completed save by its proper act. Now in the created intellectual substance we find two things, namely its substance and its being, which is not its very substance, as we have proved. (Ch. 52.) Now this very being is the complement of the existing substance, since a thing is actual by the fact that it has being. It follows, therefore, that in each of the aforesaid substances there is composition of act and potency.

Moreover. That which is received by a thing from an agent must be an act, since it belongs to an agent to make a thing actual. Now it was proved above (Ch. 15.) that all other substances have being from the first agent, and it is through having being from another that the substances thus caused exist. Consequently, being is in the caused substances as an act of theirs. But a potency is that in which there is act, since act as such refers to potency. Therefore, in every created substance there is potency and act.

Again. Everything which participates in a thing is compared to the thing participated as potency to act, since by that which is participated, the participator is made to be actually such. Now it was shown above (Ch. 15.) that God alone is essentially being, and all other things participate being. Therefore, every created substance is compared to its being as potency to act.

Further. The likeness of a thing to its efficient cause results from act, for the agent produces its like insofar as it is in act. Now the likeness of every created substance to God is by being itself, as shown above. (Ch. 6.) Therefore, being is compared to all created substances as their act. Hence it follows that in every created substance there is composition of act and potency.