Commentaria in Summam contra Gentiles, Liber I

After Saint Thomas has determined concerning the necessity of the divine will, he now determines concerning its cause ¹. And first, on the side of the thing willed; second, on the side of the will itself ².

As to the first, he does two things: first, he proves the conclusion; second, he explains it ³.

I. The conclusion is this: A reason for the divine will can be assigned.

To make this evident, it must be known that the ratio of the will is taken here for that which has the character of a cause on account of which something has, with respect to the divine will, the relation of a thing willed, as is clear in the following chapter. For where one thing is willed because of another, that because of which the other is willed is to it the ratio and cause why it is willed: just as color is said to be the formal ratio by which a stone is such as to be visible and under which it is actually seen, namely because it does not terminate the act of vision except insofar as it is colored. Hence, to say that there is some ratio of the divine will is to say that one thing willed by God is the formal ratio for another thing willed why it is willed, and terminates the act of divine volition. Which is to say that God wills one thing because of another.

II. It is therefore proved first as follows. God wills his own goodness as an end, but all other things as those which are for the sake of the end. Therefore, etc. — The consequence is proved: because the end is the reason for willing the things that are for the sake of the end.

Note that a thing is willed in the same way that it is good, since the object of the will is the good. Now that which is ordered to an end, as such, has the character of goodness only from the end: medicine is not something good, insofar as it is ordered to health, except from that very health to which it is ordered; for if the order to health were removed from it, it would no longer have the character of good in the genus of things healthy. For this reason, that which is ordered to an end does not have the character of willed and desirable, insofar as it is such, except from the end that is willed principally. And therefore it is said that the end is the reason for willing the things that are toward the end. For just as for sight one thing is the material object and another the formal object, so too for the will willing things on account of an end: the things willed materially are those ordered to the end, but the formal reason from which they have that they are willed is the end.

Second. The good of the universe is the reason why God wills each particular good. Therefore, etc. — The antecedent is proved. Because things fall under the divine will insofar as they stand within the order of the good; but a particular good is ordered to the good of the whole as the imperfect to the perfect.

Third. The reason why God wills the things that are required for each thing is that it may be that to which they are required. Therefore, etc. — The antecedent is proved. Because if God wills something, he necessarily wills those things that are required for it. But what imposes necessity on other things is the reason that that thing be: and consequently, that it be willed.

From these things Saint Thomas concludes that, in assigning the reason of the divine will, we may proceed as follows. God wills man to have reason in order that man may be; he wills man to be in order that there may be the completion of the universe; he wills the good of the universe to be in order that it may have ⁴ his own goodness.

III. In the second place he explains the conclusion ⁵, explaining at the same time how these reasons for willing, assumed in those three arguments, differ in their modes. For the divine goodness, which is set forth in the first argument as the reason for willing the universe, neither depends upon the perfection of the universe nor gains anything for itself from it. The perfection of the universe, however, which is set forth in the second argument as the reason for willing a particular good, although it depends of necessity upon certain particular goods that are essential parts of the universe, yet does not depend of necessity upon certain others; rather, from them some goodness or comeliness accrues to it. The particular good, in turn, which is placed third as the reason for willing, depends of necessity upon those things that are absolutely required for it, although it has certain things for the better.

From these things Saint Thomas concludes that sometimes the reason of the divine will contains only fittingness; sometimes utility; sometimes necessity on a supposition; but absolute necessity only when He wills Himself.

The sense of these authors is that sometimes the reason for willing is the reason for willing something as fitting to that reason itself, as when God wills the universe on account of the divine goodness; sometimes, however, it is the reason for willing something as useful to such a reason, as when God wills the non-essential parts of the universe on account of the universe itself; and sometimes it is the reason for willing something as necessary to that reason, as when God wills those things that are absolutely required for some particular good, on account of that particular good itself; for if God wills something, it is necessary that He will those things that are demanded by its essence.