Early in my monastic life, when I wanted to know everything, I read the Summa Theologiae of St. Thomas Aquinas (1225-1274), a thinker who knew everything, or seemed to. Many of Thomas’ insights and speculations continue to nourish me. The insight that I dwell upon and dwell in more than any other comes in Question 14, article 9.
Thomas has been enumerating what God knows, which, not surprisingly turns out to be everything. In article 9, however, Thomas poses the question of whether God knows everything that has never existed, does not presently exist, and never will exist. One might think that this, at least would stump God, but Thomas blithely insists that God knows these things as well. Huh?
Basically, Thomas says that God knows everything that could exist. That includes everything which God does bring into being as well as everything which God does not bring into being. This is an important point. We take our own existence and the existence of the things in the world for granted. God takes nothing for granted. God chooses some things to exist out of an infinitude of possibilities.
So what about unicorns and all else that allegedly do not exist? What does God have against them that God did not bring them into being? The answer is God has nothing against anything. The deeper answer is that God leaves many things to our imaginations. We can’t imagine horses; they are already here. But we can imagine unicorns and dragons and creatures from other planets that may or may not exist. What I find so awesome about Thomas’ insight is that God invites us to enter into God’s imagination to glimpse a few of the infinite number of beings that will never exist. God encourages us to welcome into this life many creatures we otherwise would never see and get to know. Not only do we get to pet the cats who live at our monastery, but we get to ride dragons through the air!
It is because God has invited me into small visions of the divine imagination that I can introduce you to Korniel, Pandara, Merendael, and many others. If you wish to meet them for yourself, you can read Creatures We Dream of Knowing and From Beyond to Here. Knowing them has enriched my life. I hope it will enrich yours as well.
Imaginary Visions of True Peace 
Not sure I agree. God’s omniscience has a tendency to cause certain logical problems. Like, does he know what will happen tomorrow? My philosophy is a bit rusty, but I think there was a paradox there. Anyway, it’s fascinating philosophical material.
Hi, Thank you for commenting on my post. Thomas Aquinas reconciles omniscience of the future & free will by suggesting God foresees all free choices. Einstein’s theory of relativity posits simultaneously differing time frames which makes this possibility thinkable but certainly doesn’t prove it. If the future is, as some theologians suggest, absolutely unknowable, then God’s omniscience is not compromised since God still knows everything that is knowable, including all future possibilities. The Harry Potter books deal with this paradox (without bringing God into it) with a prophecy whose fulfillment depends on how it is interpreted by those named in it and what free choices they make in relationship to it.