Commentaria in Summam contra Gentiles, Liber I

From the foregoing arguments Saint Thomas draws two corollaries¹. The first of which is: The will of God cannot extend to those things that are impossible in themselves. Concerning this, it must be noted that, just as the necessary is twofold—namely, of itself and absolutely, and by reason of another or upon a supposition—so too the impossible is twofold. That is said to be impossible of itself, or simply and absolutely, when the predicate is repugnant to the subject considered according to its own nature: as it is impossible for a man to be irrational, or for an ass to be rational. Impossible by reason of another is what is indeed possible in itself, but is impossible by reason of some adjunct, namely because the predicate is repugnant to some condition joined to the subject: as that Socrates not be sitting is indeed possible absolutely, but, given that he sits, it is for the time being impossible that he not sit. Saint Thomas therefore speaks here of those impossibles in which the predicate is repugnant to the subject absolutely. Hence he said that the divine will does not extend to things impossible in themselves: that is, to those things that are impossible by their very nature.

It is therefore proved first as follows. God necessarily wills those things that are required for what is supposed to be willed by Him. Therefore He cannot will things that are repugnant to them. Therefore He cannot will things that are simply impossible. — The first consequence is proved: because what is repugnant to something excludes something of those things that are required for it, just as being an ass excludes the rational nature of man. — The second is evident: because things simply impossible are those that have repugnance within themselves.

Second. God cannot will what is repugnant to the notion of being as such. Therefore he cannot will that affirmation and negation be true at the same time. Therefore, etc. — The antecedent is proved. Because God, by willing his own esse, wills all other things insofar as they have a likeness to him. But according to this [that] by which something is repugnant to the notion of being as such, the likeness of the divine esse cannot be preserved in it. Therefore, etc. — The first consequence is also proved. Because it is repugnant to the notion of being that something should be at once being and non-being, just as it is repugnant to the notion of man, insofar as he is man, that he should be irrational. — The final consequence likewise is clear. Because in every impossible thing per se there is included that affirmation and negation are true at the same time.

Concerning the antecedent of this argument, it must be considered that something can be repugnant to the ratio of being in one way, while in another way it is not repugnant: just as blindness, insofar as it is a negation of sight, is repugnant to being; but by reason of its substrate, it is not repugnant to being—indeed, it signifies a being, namely the eye or the animal. Therefore, what is repugnant to being cannot fall under the will in that respect in which it is repugnant to being: because such a thing does not participate in the ratio of the object of the will, which is the ratio of the good founded in esse. But by reason of the esse of something to which it is joined, it can fall under the will, as was said above² concerning non-being: for someone can will a negation insofar as he wills some being that the negation accompanies. Hence Saint Thomas added in the antecedent, insofar as it is of this kind, so as to safeguard himself against non-being insofar as it is joined to being, for in that way it can fall under the will.

Third. Things that are impossible in themselves do not fall within the intellect, since they are repugnant to themselves—unless perhaps through the error of one who does not understand the property of things; which cannot be said of God. Therefore, and so on. The consequence is evident, because the good understood is the object of the will.

It should be noted here that, just as the good is the per se object of the will, and evil cannot fall under the will except under the aspect of the good, insofar namely as it appears good, so truth is the per se object of the intellect, while the false cannot fall within the intellect unless it appears true. For what the intellect conceives about a thing, it attributes to the thing itself, insofar as it apprehends that as something belonging to the thing and judges itself to be conformed to it in understanding that of the thing. Hence it happens to it to apprehend the false insofar as it judges that to belong to the thing and to be conformed to it which either is repugnant to the thing or does not belong to it. For this reason Saint Thomas rightly says that things impossible in themselves cannot be grasped by the intellect except through the error of one ignorant of the properties of things: because, namely, from such ignorance it can come about that one judges to be true what is false. If this ignorance is removed, the intellect cannot attribute to a thing what is repugnant to it; and thus it cannot apprehend the impossible.

Fourth. Impossible things cannot be good, since they cannot be; but each thing is related to goodness just as it is related to esse. Therefore neither can they be willed. — The consequence is evident. For one wills only those things that are or can be good.