any of its attributes to be the cause of His existence; for a cause must precede its effect in being. Were either—or both—taken as the cause of existence, one of two absurdities would arise: either the thing would precede itself in existence, or it would have to exist twice—both manifestly impossible. Accordingly, even if we grant, as your argument presupposes, that His essence is other than His existence, all you have actually shown is that the essence cannot be the cause of existence.
The proof you advanced rests on the claim that things are distinguished by their essences yet share in existence and necessity. But we have already shown that essence, like existence and necessity, is divided into absolute and particular. They share only in what is absolute, not in what is particular, so that essence and existence are mutually inseparable. It is well known that two inseparables need not stand to one another as cause and effect, nor must either precede the other in any respect.
Eighth point: Suppose, for the sake of argument, that existence and necessity are universal, while the essence is particular and admits no universality, and that the universal element they share is a concomitant of the particular element in which they differ. All that follows is that existence is concomitant with the essence, so that the essence is nothing but existent. Yet if existence is its concomitant, it is not thereby the essence’s effect, coming afterward; for “concomitant” is broader than “effect”—it may be the effect of its companion, or its cause, or the effect of its cause, or simply occur alongside it.
It is also clear that when one conceives the essence of the Necessary Existent in itself as incapable of non-being, that very essence entails existence without our having to assign it any actuality prior to existence; rather, it demands existence. Indeed, it has no reality save through the existence that necessarily attends it, just as attributes have no reality apart from the subject to which they necessarily belong. An attribute is not the cause of its subject any more than the occupation of space can be realized apart from the very substance that occupies that space.