Existence itself is the broadest of universals conceived by the mind; and if reason can succeed in enumerating all of its divisions, then it is all the more capable of enumerating the divisions of any of its particular kinds. They concede all of this, and in their view it is the highest form of knowledge—so how can they maintain that elimination and exhaustive division fail to yield certainty?
An illustration of exhaustive division in the question of the Beatific Vision:
When people dispute what may rightfully be seen, some contend that the condition that makes vision possible is a purely positive mode of being; accordingly, the more perfect a thing’s existence, the more entitled it is to be seen. Others counter that the decisive factor lies in defective existence, which is closer to non-existence—such as the fact that every created thing is preceded by non-being, or that every contingent thing can lapse into non-being. In truth, the view that grounds the possibility of vision in what is shared by both the Eternal and the originated, the Necessary and the contingent, is the sounder position; for vision is pure actuality and pertains only to what exists, not to what is nonexistent. Hence, that which enjoys the most perfect, indeed necessary, existence is more deserving of being seen than what is attended by the possibility of non-existence.
For this reason light—which is more closely allied to existence than darkness—is a prerequisite for vision; and intense light, such as that of the sun, is not unseeable in itself but only because human eyesight is too weak. By analogy, our present weakness of sight prevents us from beholding God; thus Moses was unable to endure the vision of his Lord in this world. Yet it is by no means impossible in itself: God is fully able to strengthen our eyesight so that we may see Him.
If someone objects that vision is conditioned on color, spatial direction, or similar predicates supposedly impossible for God, we answer: whatever is genuinely indispensable for vision is not impossible with respect to God. When a person argues, “If He could be seen, such-and-such would necessarily follow—and that consequence is impossible,” one of his two premises must be false. The same applies to every statement reported by the Truthful Messenger—who told us that the believers will see their Lord just as they see the sun and the moon: whenever someone imagines that reason contradicts such a report, at least one of his premises is inevitably invalid.
Thus, if it is said, “Were He to be seen, He would have to occupy a place, be a body, be confined to a direction, or possess a color—and all of these are impossible for God,” we reply: all of these terms are ambiguous, and the Revealed Law has not categorically negated them.