If God is omniscient, that means God is all-knowing. There are many questions we could ask about omniscience. We could ask if we know for sure that God is omniscient. We could ask why it's supposed to be important to believe that he is. We could also ask how a being that doesn't have a body could know things about the physical world. All of those questions might be worth pursuing, but they aren't what we'll be worrying about. Our main topic will be whether the idea that God is omniscient actually makes sense.

The problem is this: leave aside necessary truths, like the truths of mathematics. Since we can learn these by reasoning, presumably God could do the same. The really puzzling question is how God could know contingent truths. Contingent truths include the laws of nature, the fact that there's a world at all, things that happen as outcomes of mechanical processes and a good deal else that's not too puzzling. After all, if God made the world, he presumably knows its laws and its original condition. That would let him figure out at least some things by doing the math, so to speak - using the laws and the original conditions to make prediction sin the manner of a sort of super-scientist. But contingent truths also include things like the decay of a radon atom or the free choices made by beings like you and me. We might wonder how God could know about those things before the event happen.

We'll start our discussion with Aquinas. Aquinas's essay is not easy to follow. These notes tell you what you need to know for purposes of exams and such.

Aquinas begins with three objections to the very idea that God is omniscient. Each objection gives a reason for thinking that God doesn't know contingent truths. It's useful to keep in mind that when Aquinas talks about contingent truths, he has in mind things that depend on other things: things that are contingent upon other things. That helps make sense of some of his points. Other things he says don't depend on this restricted interpretation of "contingent." They would apply even to things that just happen, without depending on anything (assuming there are such things.)

Objection 1: We could call this the objection from causation. God's knowledge is the cause of what God knows. (Why this should be so isn't clear, but let's assume it.) God's knowledge is necessary. That implies that it isn't contingent. But then what God knows must be necessary as well because if a cause is necessary, so is the effect. So what God knows can't be contingent. If we assume, as Aquinas seems to, that some things are contingent, it follows that there are things God doesn't know.

Objection 2: We could call this the objection from conditionals. Consider a true "if-then" statement - a true conditional. In fact, since this seems to be what Aquinas has in mind, assume that the conditional is not just true but necessarily true. If a necessarily true conditional has a true "if" clause, then the "then" cause must be true as well. Aquinas doesn't prove this, but it's correct, and we will simply accept it for our purposes.

Now take the special case "If God knew that this thing will be, then it will be." The objection holds that this is true, and necessarily so. The objection also holds that the "if" clause is necessarily true. (The reason is that "it is eternal and because it is signified as past." The point, in part, is supposed to be that what is past isn't subject to change; it must be true. But you can ignore the reason.) Therefore, the "then" clause is necessary as well. But once again, this would mean that what God knows is necessary and not contingent. And once again, if we assume, as Aquinas does, that there are contingent facts, we would have to conclude that there are things that God doesn't know.

Objection 3: We could call this the objection from the nature of knowledge. Suppose I know that there are diamonds in South Africa. If I really know this, it must be true; knowledge of false things isn't possible. So what I know must necessarily be so. However, the same goes for God, and so what God knows must necessarily be so. But contingent truths about the future aren't necessary. So, the objection concludes, God can't know future contingent things.

You should be able to give a brief statement of any one of these three objections: the objection from causation, from conditionals, of from the nature of knowledge.

There are two key ideas behind Aquinas's replies. First, we can look at a contingent thing in two ways: as it is "now" (i.e., when it happens) and "in itself" or as it is in relation to its causes. Looked at in the first way, when the thing isn't considered in its relation to its causes - we don't see it as contingent. Looked at in the other way, it is considered as contingent - contingent on its causes. Things known through their causes are known by conjecture; they're not known with certainty. And that how we view future contingent facts.

What about God? In time, contingent things come into being successively. But God doesn't see things from inside time. God knows things not just through the succession of causes. He also see things from eternity and so he knows them as they are in themselves. We are left to conjecture when it comes to contingent things. Not so for God.

That's the general idea. Now we turn to the replies.

Reply 1: Aquinas agrees that God's knowledge is the first cause. He also agrees that God's knowledge is necessary. But since things like the sprouting of a seed also have "proximate causes" (rain, warming by the sun...) these things are contingent with reference to their proximate causes. In other words, the ultimate cause really is necessary, but the proximate causes aren't. And the contingent things are contingent by reference to their proximate causes.

There's room to wonder about this reply. If God's knowledge is the ultimate cause, and God's knowledge is necessary, it's not clear why the chain of more proximate causes doesn't inherit this necessity, all the way down to the proximate causes of seeds sprouting or human choices.

Maybe Aquinas's point is that we can know future contingents only by way of their proximate causes, and so they are contingent from our point of view. We don't have access to God's knowledge. This would mean that whether a thing is contingent or not depends on the point of view it's seen from. All you need to remember is this:

Even if God's knowledge is the ultimate and necessary cause of everything, many things also have proximate causes. When we say the things are contingent, we mean that by reference to these proximate causes.

How does this help? Aquinas says that when we're talking about things in relation to the mind or soul, we're talking about them not as they are in themselves, but as they are "in the mind." When we say "If God knew this future thing, then it will be", we are talking about the future thing as it falls under God's knowledge - as it is in God's mind. From that point of view, it's known as something present to God's mind, and hence as necessary. But the thing itself can still be contingent qua physical thing with proximate causes.

This is not very easy to evaluate or even to understand, but all you need to remember is this:

When the "if" clause of a statement refers to God's knowledge, then we aren't talking about the thing known as it is in itself, but as an item of God's knowledge. In that sense what God knows is necessary and in that sense the "then" clause is necessary too. But the thing known is also contingent considered not as it is "in God's mind" but in relation to its proximate causes.

Reply 3: The objection was that what we know must necessarily be. But this also applies to God. Since no future contingents must necessarily be, and since what God knows must necessarily be, God can't know future contingents. The reply points out that when we know something, we don't make it necessary in itself. If I know right now that there is a noise in the background (because I hear it), then because I can't know false things, the noise "must" be there. But once again, this is only relative to my knowledge. The noise is still contingent relative to its proximate causes.

Unlike us, God sees everything "at once" from the perspective of eternity. That means God knows things that are future and contingent from our point of view. The fact that he can know them at all is a result of his eternal nature - his position "outside time." For our purposes, this is the most important idea in Aquinas's discussion.

God can know things that are future and contingent from our point of view because God "sees" everything at once, from outside time. This is why God can know future contingents even though we can't. These future contingents are not contingent qua items of God's knowledge, but considered in relation to their proximate causes, they are contingent.

In the next set of notes, we consider some further issues about God's knowledge. Later we will also need to talk more about what it means to say that God is outside time. for now, however, we have a story about how God can know things that are genuinely contingent.

- Allen Stairs