Commentaria in Summam contra Gentiles, Liber I

From the preceding conclusion Saint Thomas deduces as a corollary¹ that a multitude of things willed is not repugnant to the unity and simplicity of the divine substance.

It is proved first as follows. If several things willed were to introduce into God any multiplicity, there would not be in Him a single act of the will. The opposite of this has been shown. — The consequence is evident. For acts are distinguished according to their objects.

Note that from this proof Saint Thomas wishes to have it that what is distinguishable in proportion to the object is act: and therefore, if several objects make some plurality, that plurality will be a plurality of acts. He does not, however, intend that acts are multiplied by whatever several objects there may be. Hence the sense of that proposition is that act is what is properly and first multiplied when a plurality of objects induces some plurality.

Second. All things are one in the divine goodness: because some things² are in it according to its mode, namely, material things immaterially and many things unitedly. Therefore, and so on. — The consequence is proved. Because things are related to the will of God in the same way that they are comprehended by his goodness: since God wills other things insofar as he wills his own goodness.

Note that all things are said to be one in the goodness of God insofar as the divine goodness is the exemplar of all goodness: not, however, because they agree in some one goodness produced by God.

Third. A multitude of intellects does not introduce multitude into the divine essence, nor composition into its intellect. Therefore, etc. — The consequence is evident. For the divine intellect and the divine will are of equal simplicity, since each is the divine substance.

Fourth. Appetite is such as it is directed toward an appetible thing, insofar as the appetent seeks in it that wherein it may rest ³. Therefore, etc. — The antecedent is evident from the difference between cognition and appetite. And also from the authority of Aristotle, who says in Book VI of the Metaphysics that good and evil are in things, but true and false are in the intellect. — But the consequence is proved as follows: because that something should be related to many things does not conflict with its simplicity; whence unity is also the principle of many numbers.