Commentaria in Primam Partem Summae Theologiae

In the title, it is clear that the question concerns formal inherence: namely, whether any accidents are formally in God. And the discussion is about real accidents, and not about accidents, that is, predicates taken accidentally, insofar as "accident" is a name of second intention and is posited as the fifth Predicable.

II. In the body, a single conclusion, answering the question in the negative: In God there cannot be an accident. – It is proved in three ways. First. God is pure act: therefore no accident. Second. God is subsistent being itself (ipsum esse): therefore no accident. Third. Because an accident would be either accidental per accidens or essential per se: not the first, since God is the first being (primum ens); nor the second, since God is the first cause.

III. Concerning the second argument, note that, just as between the abstract and the concrete according to the understanding there is this difference: that the abstract as such admits nothing alongside itself according to the understanding, whereas the concrete is permitted to be mixed with many things (for it is not unfitting to understand whiteness to be sweet, etc.; but whiteness as such excludes from itself everything other than itself: for nothing else is that by which something is white than whiteness; but what is white is sometimes also something other than white, say a sweet apple, etc.); so too between the abstract in reality and the composite in reality there is this difference: that a thing abstracted in reality is itself alone; but a composite thing admits something alongside itself which is not itself. And therefore this perfection which esse signifies, if it is posited as abstracted in reality from everything in which esse is receivable, that is, from every generic nature, is hard esse: and it admits nothing besides itself within itself: and consequently it can have no accident. But the composite of esse and nature, which is called that which is, is permitted to have something besides itself within itself. And this is what the text says: that esse itself, because it is abstract and that-by-which, has nothing joined to itself, like heat; but that which is, because concrete and that-which, can have something extraneous, as what is hot is also white.

IV. Concerning the third argument, note that each member proceeds from its own proper principle. For the root of the first is that an accident per accidens naturally presupposes an accident per se: since universally, under whatever order of things, that which is per se is prior to that which is per accidens, as is said in Book II and Book VIII of the Physics¹ – But the root of the second is that universally the first altering thing is altogether unalterable: and the first mover locally is altogether immobile locally: and consequently the first cause is altogether uncaused. It would not, however, be altogether uncaused if it had anything caused within itself, as is evident, etc.

V. In response to the first, you have an excellent gloss of that saying, "what truly is, is predicated of nothing as accidental": — taken univocally; but taken analogically, something is substance in one and accident in another, as is clear in the case of wisdom.