My thesis, then, is that classical theism is a type of idealism; it is onto-theological absolute idealism. If everything concrete is created originally and sustained ongoingly ex nihilo by a purely spiritual being, an Absolute Mind, and by purely spiritual activity, then this is better denominated 'idealism' than 'realism.' Is that not obvious?
This brings to mind Exodus 3: 14. When Moses asks God who he shall tell the Israelites sent him, God answers: “I AM WHO I AM. This is what you are to say to the Israelites: ‘I AM has sent me to you’” This has always struck me as philosophically centuries ahead of its time, the sort of thing that no one at that time could have made up. (I studied scholastic philosophy and existential phenomenology under a great and wise Jesuit; so I am at least philosophically literate.)