Introduction by Bob Pasnau

Thomas Aquinas says: “Objection. [E]verything known by God must necessarily be, because even what we ourselves know, must necessarily be; and, of course, the knowledge of God is much more certain than ours. But no future contingent things must necessarily be. Therefore no contingent future thing is known by God. On the contrary, It is written (Psalm 32:15), "He Who hath made the hearts of every one of them; Who understandeth all their works," i.e. of men. Now the works of men are contingent, being subject to free will. Therefore God knows future contingent things.”

Original Latin

Defining Omniscience

Almost any conception of God, and certainly any Christian conception of God, accepts that God is all-knowing, or omniscient. But it is not as easy as it might seem to explain just what omniscience involves.

As a first approximation, to be omniscient would seem to consist in knowing everything that is true. But this raises tricky questions about the future, especially events in the future that are contingent - events that may or may not occur. Does God know them?

One reason to think God might not know future contingents is that they might seem not even to be true yet. For instance, there just seems no fact of the matter, yet, about what you will have for breakfast tomorrow. This way of thinking of the problem would let us say that God is omniscient - knows everything that is true - and still does not know the future. But this is a conclusion Christian theologians like Aquinas have not wanted to embrace, because it does not seem consistent with God's providence - that is, God's active role in directing events in the world for the best. To do this, it would seem, God must know the future, and even know contingent future events.

Is the future pre-determined?

But if this is so, then a problem looms: for God to know that these future contingent events will occur, it must be true that these events will occur -- only truths are known, after all. Yet, if it is true, then it seems no longer to be contingent at all, but to be necessary. This is highly problematic. For one thing, it simply does not match our conception of how the world is, since we take many events in the future to be contingent.

Perhaps more seriously, it also seems to threaten human freedom. If God already knows what we will do, then it is hard to see how we do it freely. This is an old philosophical problem, going back well before Aquinas. In the excerpt here, Aquinas offers one of the best known attempts to reconcile human freedom with divine foreknowledge.