But why can’t we say this: God is composite, but composite in a way that doesn’t conflict with His aseity or unity. We can’t conceive of such a composite being, but then we can’t conceive of a wholly simple being either.
I’m not claiming God is composite. The question I’m raising is about the “location” of the Creator-creature distinction. Do we have to draw it between the simple being of God as opposed to the composite being of creatures? Or might we draw it between two different sorts of composite beings, one divine and one human? What difference would it make?
The obvious answers that have been given for literally over a thousand years by Christians, Jews, and Muslims are, respectively, Yes (but you can also draw it between immutability and mutability, infinity and finitude, necessity and contingency, and the like, because these distinctions are interdefinable), No, and Because It Would Be Incoherent to Do the Latter (in part because of the previous point, that divine simplicity is interdefinable with a number of other doctrines) and Because It Would Also Be Pointless to Do the Latter (because it is natural and practically universal to point to composition as a reason for taking something to be created).
But Leithart is not giving up:
The claim is now that “composite” means the same thing for God as for creatures. It seems that simplicity is needed if we’re going to describe God in terms of a metaphysics that’s drawn from created being. But if divine metaphysics are unlike created metaphysics, why can’t “composite” be used, differently, of each. Why can’t we say God is “composite,” understood analogically?
No, this is not how analogical predication works. Analogical predication requires that the term in question have a unity of meaning in both cases, but involving the reference of one to the other (or of both to a third). To use the word 'composite' analogically, we would have to be able to refer to God as first and most composite being, so that 'composite' applied to creatures would have a built-in reference to Him. But this is not how 'composite' works in any language, including English; the more composite a thing is, the more multitudinous and divided its parts. The less divided its parts, the simpler a thing is. Simplex means not multipliable into many, which is true of God; compositus, its opposite in this context, means built out of multiple things. That 'composite' means that something is built is not itself a fatal problem (e.g., simply considering it on its own, it could be parallel to perfectus, which means completed), but removing the 'built' component makes it a metaphor in particular, and when we look at how it would have to apply to God, it's quite clear that God would have to be more one than creatures, and thus more simple, not more composite. Everything Leithart says about how the divine composition would have to differ from creaturely composition simply underscores this very point.
What Leithart is proposing is not analogical predication but equivocal predication. You could, certainly, use the word 'composite' of God; you can use words like 'fire' and 'rock' of God, too. But it's not going to be in any sense inconsistent with the doctrine of divine simplicity, because it's not what anyone means when they are talking about the doctrine of divine simplicity; and, in addition, it's obviously going to confuse people when you just shuffle around the words everyone has been using for centuries, for no good reason. Remove not the ancient landmark which thy fathers have set, Leithart.