FROM THOMAS FLINT, PROFESSOR OF PHILOSOPHY AT THE UNIVERSITY OF NOTRE DAME: Perhaps the first thing to note about the question “How could God know the future?” is that it could be taken in two very different ways. First, by emphasizing the "How,” one might think the question is asking for an explanation of something that we know occurs—i.e., as asking, “Given that God knows the future, what accounts for or explains God's knowledge?” So understood, the question is akin to asking of a magician, “I know you made her disappear, but how did you do it?” Alternatively, by emphasizing the “could,” we might take the question as implicitly challenging the claim that God does know the future—as asking, rhetorically, “Why on earth think that God knows what’s going to happen?” Understood in this second way, the question is similar to reacting to a friend’s suspicions by asking plaintively, “How could I betray you?” On the contemporary philosophical scene, the question, taken either way, has been much discussed.
Those who call themselves "open theists" deny that God has comprehensive knowledge of the future. In particular, they deny that God can know what people will freely do. Some open theists think that there simply are no facts about future free actions; others say that, though there are such facts, there’s no way anyone can know them, or at least no way God can know them, since God's knowing now that I will do such-and-such tomorrow would entail that I’d have no alternative but to do such-and-such tomorrow, and thus wouldn’t do it freely. All open theists, though, agree that God’s knowledge of the future is quite limited, and hence that God needs to take risks in interacting with creation.
Open theism, though, is very much a minority view among those engaged in philosophical theology. The far more traditional view—that God, being omniscient, has perfect and complete knowledge of the future—is still dominant. But traditionalists are hardly united in their explanations of how God knows the future.
One traditional explanation holds that God knows what will happen in time because God isn’t in time. The doctrine of divine eternity holds that God is not limited, as we are, by temporal or spatial boundaries. God's is a perfect life, not one balanced on the knife’s edge of the present, the barely existing dividing line between the no-longer-existent past and the not-yet-existent future. God’s being outside of time, these "eternalists" say, affords God perfect access to every moment in time, much as (to use a favorite eternalist metaphor) an observer on a mountaintop can see in one glance every member of a single-file troop marching below him, while those involved in the march have a much more limited perspective. According to eternalists, speaking of divine foreknowledge is at best misleading. God knows what, from our perspective in the march of time, is in the future—but it’s not future to God.
Many traditionalists, though, find the eternalist explanation of how God knows the future unsatisfying. The observational metaphor it employs, they argue, points to a God whose knowledge of the future is purely passive. But the God of traditional monotheism, they insist, isn’t one who just likes to watch: God’s an active creator, the providential sovereign whose world develops as it does because God planned that it so develop. So even if God is outside of time, we can’t use that to explain God's knowledge of the future.
Traditionalists who adopt this line have developed it in two very different directions. Some suggest that God knows the future because God determines everything that takes place. As the “first cause,” God has complete understanding of the causal ramifications, both short run and long term, of all that God does. Everything that occurs, then, can be traced back to God's own creative intentions; in knowing God's intentions, God knows our future. The metaphor of the author is sometimes used to explain how this divine determination is compatible with our freedom. An author decides how a character in her novel behaves, but in the world of the novel, the character can still be acting freely.
Other traditionalists find this account bizarre. If God is determining how we act, then we’re just fooling ourselves if we pretend that we have genuine freedom. God exists and acts in our world, not in a separate authorial plane. So if God’s causing us to act as we do, then we’re simply not free. The only way to reconcile God’s active foreknowledge with our genuine freedom, they say, is to see God's providence as acting through the knowledge of how we would freely respond if God were to put us in various situations. Knowledge of this sort is often called "middle knowledge," since, as knowledge of what would happen, it can be thought of as located between knowledge of what could happen (knowledge of what’s possible) and knowledge of what will happen (knowledge of what’s actual). A God who has middle knowledge and decides which situations we will be in, the advocates of this position contend, would know all that we will freely do—and know it without causing it, thereby safeguarding our freedom.
This “middle knowledge” answer to the question of how God knows the future has many advocates (including me), but also many critics, who charge (among other things) that there’s simply nothing in the world that could ground the sort of what-would-happen-if truths that middle knowledge requires.
So the issue of divine foreknowledge is one that is currently quite unsettled among philosophers and theologians. Where will this discussion head in the future? Only God knows. Perhaps.

Thomas Flint appears with Russell Stannard, John Polkinghorne, Ernan McMullin, Greg Boyd, and William Lane Craig in “How Could God Know the Future?” the 27th episode in the Closer to Truth: Cosmos, Consciousness, God TV series, hosted and created by Robert Lawrence Kuhn. The series airs Thursdays on the PBS HD network and many other PBS stations. Every Friday, participants will share their views on the previous day's episode.