I’ve recently begun reading about Aristotelean-Thomistic philosophy. In A-T metaphysics, the doctrine of divine simplicity has a central place. This is the doctrine that God has no parts, be they physical or metaphysical. From this it follows that he is identical to his nature, to his existence, and to each of the divine attributes. Now this may sound really strange to some, but I recently read the SEP article on Divine Simplicity, and the distinction between constituent and non-constituent ontologies is both informative and helpful in making sense of divine simplicity. Worth a read.