Ipsum esse subsistens

I suppose many people imagine that Christians think of God as some sort of Super-Being among the many beings and realities his science studied. But that is exactly wrong. God, as Christians ought to know (and preach, and teach), is not the supreme instance of the class of beings known as superheroes in Marvel comic books. No, as Thomas Aquinas taught more than seven centuries ago, God is ipsum esse subsistens: God is sheer Being itself, which makes it possible for everything else “to be.”