“If God is omniscient He must have known what Abraham would do, without any experiment; why, then, this needless torture? But as St. Augustine points out, whatever God knew, Abraham at any rate did not know that this obedience would endure such a command until the event taught him; and the obedience which he did not know that he would choose, he cannot be said to have chosen. The reality of Abraham’s obedience was the act itself; and what God knew in knowing that Abraham “would obey” was Abraham’s actual obedience on that mountain at that moment. To say that God “need not have tried the experiment” is to say that because God knows, the thing known by God need not exist”
God wills to know the actual, lived-out reality of our preference for Him over all things. And He wills that we have the testimony of our own authenticity through acts of actual preference of God over his gifts. Lewis is right that God may as well not have created the world, but only imagined it, if his knowing what “would be” is as good as his knowing it in the very act. God wills that He have an experiential-knowing, an actual seeing-knowing, a watching-knowing. A real lived-out human act of preference for God over his gifts is the actual lived-out glorification of God’s excellence for which He created the world.
taken from “A Hunger for God”