Commentaria in Primam Partem Summae Theologiae

In the title there is nothing difficult. Highest adds the relation of supreme excess: so that it is the same whether it is the highest good, or whether it is a good exceeding all other goods, both in act and in potency.

II. In the body of the article there is a single conclusion, answering the question in the affirmative: God is the highest good simply speaking.

This conclusion is first explained, then proven. It is explained by distinguishing, implicitly, between the highest good simply speaking and the highest good in a genus. The highest good in a genus is that which surpasses the others in that order of things: as human happiness is the highest human good, surpassing all other human goods; and so with the rest. The highest good simply speaking, however, is that which holds the supreme place throughout the whole breadth of beings (entia). And therefore the term simply is added in the conclusion.

It is proved, however, thus. Goodness belongs to God as the first effective cause of all things, not univocally: therefore it belongs to him most excellently: therefore he is the highest good simply speaking. – The antecedent, in both its parts, is clear from what has been said. But the first consequence is proved from the difference in the mode of being of the effect in a univocal cause and in an equivocal or analogous cause: for in a univocal cause it exists in the same mode, but in an equivocal cause in a more excellent one.

III. Note, however, that the effect's being in an equivocal cause in a more excellent manner occurs in two ways: one way, formally and virtually at once; another way, virtually only. An example of the first: light and diaphaneity in the heavenly bodies, with respect to inferior bodies. An example of the second: heat in the sun and in inferior bodies. In our case, we are speaking of an effect preexisting in its cause not only virtually but also formally: hence God is good both formally and virtually. The force of this argument rests on this, that each effect of an equivocal cause is in that cause itself in a more excellent manner than it is in the effect. And therefore the text speaks indistinctly of the mode of being of the effect in the equivocal cause, since this sufficed for the intended point, namely, that goodness belongs to God in the most excellent manner. For already in the preceding article it had been established that goodness belongs to him formally.

IV. In response to the second, note that the reply consists in the conversion of the proposition: good is that which all things desire, that is, that which all things desire is good.

V. In response to the third, note that things of different genera are said to be in no way comparable when they are taken as such, that is, insofar as they are in different genera. For if they were taken according to some predicate in which they would agree, they could be compared.