Commentaria in Primam Partem Summae Theologiae

A clear title. - In the body, two parts: first, the responsive conclusion answering the question affirmatively; second, an epilogue on the antecedents 1.

II. As to the first point, the conclusion is: God's understanding is His substance. — It is proved in two ways. First, by leading to an impossibility, with Aristotle. If God's understanding were other than His substance, it would follow that the divine substance would stand to something else as potency stands to act and perfection: this is impossible; therefore, etc. — The consequence is proved: because understanding is the perfection and act of the one who understands.

Second, it is proved ostensively. The substance of God is His own esse, and His own intelligible species; therefore God's understanding is His substance. — The antecedent, as to the first part, is clear from question 3; as to the second, from the second article of this question. But the consequence is proved. Understanding is an act remaining in the one who understands, just as esse: therefore, if the substance of the one understanding is his own esse and the intelligible species itself, it must be that he is his own understanding. The assumption is proved: because understanding follows upon the species, as esse follows upon form.

III. For the evidence of the consequence, together with its proof—since it is somewhat hidden on account of its depth and formality—three things must be noted 2. First, that in the text four things are said about understanding: namely, that it remains in the one understanding; that it is as act and perfection of him; that it is as being (esse) is the act of the existent; that it follows the intelligible species as existing follows form. Of these, the first two are not proved, because they are clear. The third, however, is proved by the fourth, which was left aside as commonly admitted. Note secondly, that the fourth statement, namely that understanding follows the intelligible species as being (esse) follows form, is verified in three respects, as far as the matter at hand is concerned. First, with respect to causality: since form is the reason of being (essendi), and the intelligible species is the reason of understanding. Secondly, with respect to necessity: since actual form necessarily has existence accompanying it; and the intelligible species in act—not in a middle state between potency and act—necessarily has understanding accompanying it. Thirdly, with respect to the mode of causing: since form, by completing what it is, makes being (esse); and the intelligible species in act, not in the genus of being (entis) but in the genus of the intelligible, by completing the intellect makes understanding, as can be seen from article I of this question ¹, and from what was said in question XII ². From these things, however, and especially from this last one, the third statement of the text, which is the effect of this fourth, becomes clear. For from these it follows that understanding is the perfection of the one understanding just as existence is the perfection of the existent; that is, understanding perfects the one understanding in the same proportion in which being (esse) perfects the existent; indeed, understanding is the very being (esse) of the one understanding in the genus of the intelligible, just as being (esse) is the very being (esse) of a being (entis) in the genus of beings (entium). Note thirdly, that the divine substance is form, indeed pure act, both in the genus of beings (entium) and in the genus of intelligibles. And by reason of the first, it is the reason of being (essendi), and is called a being (ens); but by reason of the second, it is the reason of understanding, and is called form or intelligible species. Hence God's being (esse) corresponds to his substance as pure act in the genus of beings (entium); while his understanding corresponds to the same substance in the genus of intelligibles. And proportionately thus: that understanding is the being (esse) of the divine substance as an intelligible species in the genus of the intelligible, just as existence is the being (esse) of the same substance in the genus of beings (entium). And therefore the consequence, together with its proof, was excellent and formal, arguing from the concurrence of both forms into one, and from the identification of that one with its proper being (esse) according to one genus. For from these two things assumed in the antecedent—first, that the substance is itself the intelligible species, and hence is form in both genera; second, that the substance of God is its own being (esse), and hence identifies to itself being (esse) in the genus of beings (entium)—it is inferred, therefore, that it must also be ³ its own understanding; that is, that it identifies to itself the being (esse) that belongs to it in the genus of the intelligible. For the efficacy, infinity, or actuality of the divine substance is no less in the genus of the intelligible than in the genus of beings (entium). And if the opposite were said, it would follow that it would not be pure act in the genus of the intelligible. For intellect in act in the genus of the intelligible, which encloses within itself the nature of knower and known as such, is related to understanding as potency to act, as a being (ens) to being (esse). IV. As for the second point ⁴, the epilogue uniting the threefold identity is clear, along with its corollary, which holds that God's very being (esse), as intelligent, introduces no diversity in God. All things are clear.