Translation: Aquinas on powers 1

Thomas Aquinas
Summa Theologiae
Part I, question 77, article 1
Is the mind the same as its power?

In response, it should be said that it is impossible for the essence of the mind to be its power, although some postulate this. For our present purposes, this can be shown in two ways.

First, since potentiality and actuality divide every genus of being, it is necessary that potentiality and actuality refer to the same genus. For this reason, if an act is not in the genus of substance, then the power which is spoken of with respect to that act cannot be in the genus of substance either. However, an operation of the mind is not in the genus of substance, with the sole exception of God, in whom his operation is his substance. Whence, the power of God, which is the source of his operation, is the divine essence itself. But this cannot be true of the mind, nor can it be true for any creature, as I said above when I discussed angels.

Second, that this is impossible for the mind is obvious. For the mind, in terms of its essence, is actual. Thus, if the essence of the mind itself were the immediate source of its operation, it would perform vital operations so long as it were actually existent, just as the mind is always living and actual [so long as it exists].

For insofar as it is a form, it is not an actuality that is ordered to the final act, but it is the ultimate terminus of generation. Whence, even when it exists, it is still in a state of potentiality with respect to some other actuality, and this belongs to it not in terms of its essence, i.e., insofar as it is a form, but rather in terms of its potentiality. In this way, then, the mind, insofar as it stands under its power, is said to be the 'first actuality', and it is ordered to its 'second actuality'.

However, one can easily see that everything which has a mind is not always actually performing its vital operations. Whence, even when the mind is defined as the actuality of a body that has the potential for life, nevertheless, that potentiality is not destroyed by the presence of the mind. It must be the case, then, that the essence of the mind is not the same as its power. For nothing is potential on account of its actuality, insofar as it is actual.