Commentaria in Primam Partem Summae Theologiae

In the title, ly essence signifies the deity, which would be imported by a definition of God, if God were defined: ly being imports the signification of ly is as the second term of the proposition, as when we say “God is,” and likewise “a human being is,” and so on: ly the same imports real identity. So that the sense is: Whether the thing signified by ly God is the thing signified by ly is, when it is said God is.

And know that this question is most subtle, and proper to the ancient metaphysicians: but very foreign to the moderns, because they hold not only in God, but in every thing, that essence is identified with that thing's existence. Let this, then, be our question: for others it will be a special question, concerning the distinction of esse from essence universally¹.

II. In a single body, one conclusion: God is His own esse. – It is proved in three ways. First. God is the first efficient cause: therefore He has esse not caused by anything extrinsic: therefore He is His own esse.

The antecedent is clear from what has been said². – The first consequence is clear from the terms. – But the second is proved. Everything fitting to a thing that is distinct from its essence is either caused by the essence alone or by something extrinsic: therefore, if esse is distinguished, it is caused either from within or from without. But that it be caused from within alone is impossible, because nothing is a sufficient cause of itself so as to be. Therefore, if it is not caused by something extrinsic, it is identical with the essence. This is the consequence to be proved.

III. Second. God is pure act: therefore his essence does not stand to esse as potency to act: therefore he is his own esse. – The antecedent is evident. And the first consequence is known from the terms. The second is proved. Esse is the actuality of every form or nature: therefore every nature distinct from esse is compared to it as potency to act: therefore, if it is not compared as potency, it is esse itself. The assumption is proved: because nothing is signified in act unless it is signified as it is.

Note here that this argument is founded on the fact that whatever quiddity or nature, however actual it may be according to its quidditative character, when related to esse has the character of potency: for wisdom and goodness, etc., are actuated by that which I say is; and likewise humanity and equinity, etc. And therefore it is also said that esse is the actuality of every form; and that no nature is signified in ultimate act except insofar as it is signified as esse in exercised act.

IV. Third. God is the first being: therefore He is a being by essence: therefore He is His own esse. – The antecedent, together with the first inference, is evident. The second, however, is proved by the destruction of the consequent, in two ways. First, from the quiddity of the name being by essence, thus. It is not its own esse: therefore it has esse and is not esse itself: therefore it is a being by participation: therefore it is not a being by essence; just as if it has fire and is not fire, etc. Second, God is not His own esse, and He is His own essence: therefore He is not a being by essence, but by something added. – All things are clear.

V. In response to the second objection, a difficulty arises: for the reply seems to imply two contradictories. For if we know that this proposition is true, God is, then we know that it is so in reality, namely that God is; but this is to know the esse that is in God Himself; therefore.

To this doubt (which we treated at length in II Poster., chapter I, and which Scotus, in I Sent., distinction III, question I, at the beginning, adduces while censuring this response), it is briefly said that this response is the best one, and unique to God. For in this the esse of God differs from the esse of other beings: that the esse of God is the quod quid est of God himself, as is determined here; so that the proposition Deus est holds in the first mode of saying per se. But the esse of the others does not stand thus, but is distinct from their quiddities. And from this it arises that the esse of God, in itself and absolutely, is the proper terminus of the question quid est: and it is the terminus of the question an est, secundum quid, that is, as grounding the truth of the proposition. But the esse of others does not pertain to the question quid est, because it is not a predicate of the first mode, as appears inductively, homo est, caelum est, etc.: but in itself and simply it pertains to the question an est. And therefore, when concerning other things we know the question an est, we are said to know the esse that signifies the truth of the proposition, and the esse of the thing itself: because it is known according to its proper mode in which it is knowable. But when concerning God we know an est, we are said to know the esse that signifies the truth of the proposition, and not to know the esse of God: not because the ultimate terminus of our cognition is the esse of the proposition, as the objection understood (since the terminus is the esse of God, not absolutely, but as answering to the truth of the proposition); but because through this cognition the esse of God is not known by the proper question by which it is knowable in itself, since it is not known per quid.