Brian Leftow writes:
“Let us put this belief about God’s existence a bit more formally: it is part of the ordinary theist’s concept of God that no regress of true explanations can go past God’s existence, i.e. that when one has traced some phenomenon back to the fact that God exists, one can go no further. Philosophically sophisticated theists who defend versions of the ontological argument might hold to a slightly different claim. If some ontological argument is sound, then (some may say) God exists because it is His nature to exist. Thus such philosophers would perhaps say that chains of true explanations can go past God’s existing to God’s having His nature, but no further.”
~Brian Leftow, Is God an Abstract Object?
He goes on to argue against this later suggestion by advancing the identity thesis implied by divine simplicity, according to which God is identical with all his attributes (and with this I strongly agree). However, consider the following question: why does the world exist? If we come to God as the explanation, then it seems as though we’re saying (where G=God and W=World) G⊃W. However, that can’t be what we’re saying because, at least on the Christian view, God Libertarian-freely chose to create the world, such that he did not have to (nothing in God’s nature [i.e., about him] constrained him to create). However, doesn’t that make the ultimate explanation of why the world exists not ‘God’ but rather ‘that God Libertarian-Freely chose to create’?
I don’t think it does. Let us say with Pruss that even Libertarian-Free acts have sufficient explanations, such that if Susie Libertarian-Freely chose A, then the sufficient reason for Susie’s choosing A is just the set of all reasons Susie had for choosing A. Therefore, we can explain God’s Libertarian Free choice to create the world in terms of all the reasons God had for Libertarian-Freely choosing to create. These reasons, however, will all be purchased from God’s Nature (which, recall, is identical to God). Thus, the sufficient reason for God’s Libertarian-Freely choosing to create is found in God’s nature (i.e., in God), and in this manner the ultimate explanation of why the world exists traces back to God without tracing back to anything ‘behind’ God (since God lies behind the Libertarian-Free decision to create).