Thursday, March 21, 2019

If classical theism rules out open theism, then classical theism rules out presentism

If presentism and most, if not all, other versions of the A-theory are true, then propositions change in truth value. For instance, on presentism, in the time of the dinosaurs it was not true that horses exist, but now it is true; on growing block, ten years ago the year 2019 wasn't at the leading edge of reality, but now it is. The following argument seems to show that such views are incompatible with classical theism.

  1. God never comes to know anything.

  2. If at t1, x doesn’t know a proposition p but at t2 > t1, x knows p, then x comes to know p.

  3. If propositions change in truth value, then there are times t1 < t2 and a proposition p such that p is not true at t1 and p is true at t2.

  4. It is always the case that God knows every true proposition.

  5. It is never the case that anyone knows any proposition that isn’t true.

  6. So, if propositions change in truth value, then there are times t1 < t2 and a proposition p such that God doesn’t know p at t1 but God does know p at t2. (by 3-5)

  7. So, if propositions change in truth value, God comes to know something. (by 2 and 6)

  8. So, propositions do not change in truth value. (by 1 and 7)

I think the only controversial proposition is (1). Of course, some non-classical theists—say, open theists—will deny (1). But non-classical theists aren’t the target of the argument.

However, there is a way for classical theists to try to get out of (1) as well. They could say that the content of God’s knowledge changes, even though God and God’s act of knowing are unchanging. The move would be like this. We classical theists accept divine simplicity, and hence hold that God would not have been intrinsically any different had he created otherwise than he did. But had God created otherwise than he did, the content of his knowledge would have been different (since God knows what he creates). So the content of God’s knowledge needs to be partially constituted by created reality. (This could be a radical semantic externalism, say.) Thus, had God created otherwise than he did, God (and his act of knowledge which is identical to God) would have been merely extrinsically different.

But exactly the same move allows one to reconcile the denial of (1) with immutability. The content of God’s knowledge is partially constituted by created reality, and hence as created reality changes, the content of God’s knowledge changes, but the change in God is merely extrinsic, like a mother’s change from being taller than her daughter to being shorter than her daughter solely due to her daughter’s growth.

I agree that denying (1) is compatible with God’s being intrinsically unchanging. For a long time I thought that this observation destroyed the argument (1)-(8). But I now think not. For I am now thinking that even if (1) is compatible with immutability, (1) is a part of classical theism. For it is a part of classical theism that God doesn’t learn in any way, and coming to know is a kind of learning.

Here is one way to see that (1) is a part of classical theism. Classical theists want to reject any open theist views. But here is one open theist view, probably the best one. The future is open and propositions reporting what people will freely do tomorrow are now either false or neither-true-nor-false, but tomorrow they come to be true. An omniscient being knows all true propositions, but it is no shortcoming of omniscience to fail to know propositions that aren’t true. Then, our open theist says, God learns these propositions as soon as they become true. This is all that omniscience calls for.

Now, classical theists will want to reject this open theist view on the grounds of its violating immutability. But they cannot do so if they themselves reject (1). For the presentist (say) classical theist can reject (1) without violating immutability, so can our open theist. Indeed, our open theists can say exactly the same thing I suggested earlier: God changes extrinsically as time progresses, and the content of God’s knowledge changes, but God remains intrinsically the same.

So, what do I think the classical theist should say to our open theist? I think this: that God doesn’t come to know is not just a consequence of the doctrine of immutability, but is itself a part of the doctrine of immutability. A God who learns is mutable in an objectionable way even if this learning is not an intrinsic change in God. But if we say this, then of course we are committed to (1), and we cannot be presentists or accept any other of the theories of time on which propositions change in truth value.

I think the best response on the part of the classical theist who is an entrenched presentist would be to deny (1) and concede that classical theism does not rule out open theism. Instead, open theism is ruled out by divine revelation, and revelation here adds to classical theism. But it seems very strange to say that classical theism does not rule out open theism.


Sean Killackey said...

Do you have a brief resource to explain the B theory of time, such am essay?

Also, why does it seem as if the present lasts for a brief while (assuming presentism is true), if the present can't be extended in time? What do presentists say? I've always wondered how long the present is; a while back I found some notes I wrote while I was still in high school, if even then. My conclusion was not very enlightening, though I did speculate that there was no real present as over and above the past and present.

Unknown said...

Dr. Pruss

I was just wondering if you have a Facebook? There is a group called: The Thomism Discussion Group filled with many academics, philosophers and graduate students that discuss a lot of relevant topics that you are interested in. Some members currently include: Dr. Patrick Lee, Dr. Eleonore Stump, Dr. Robert C. Koons, Dr. Robert T. Anderson among others. I think your thoughts would be a welcome addition to the group.

Unknown said...

Does this presuppose that we should think of God’s knowledge as involving a relationship between His mind and a proposition?

If so, I feel like Alston has some pretty straightforward arguments for why we shouldn’t think this is the case. (

Alexander R Pruss said...


I don't know. Maybe:

I think the evanescence of the present is a problem for presentism.


I have a Facebook account, but I almost never use it. The main exception is if I need to look at information regarding a business or organization that doesn't have a proper website.

Mr. Davis:

I don't think the argument presupposes that. It does require that God knows propositions--i.e., God knows that the sky is blue, that 2+2=4, and so on--but whether that knowledge is constituted by a relation between God and the proposition is a separate question.

Alexander R Pruss said...

Mr. Davis:

One way to avoid the metaphysical questions about how God's knowledge works is to just substitute a particular proposition in for p in the argument, as well as particular times t1 and t2. For instance, we can suppose that p = "There exist horses", t1 = 100 million years ago, t2 = now. Then if presentism is true, it was true at t1 that God doesn't know p, and it is true at t2 that God knows p, so God gained a piece of knowledge, which is contrary to classical theism.

JohnD said...

Based on the definition of "comes to know" given in (2), I think a denial of (1) is plausible.

God can "come to know" in this very thin sense without the content of his knowledge changing. In other words, it can both be true that A) he knows all true propositions in one eternal vision and B) he "comes to know" a particular proposition that was neither true nor false until a particular time t*.

Classical theists can reject the open theist view if they have a stronger version of omnipotence that includes all true propositions that will ever be true.


Alexander R Pruss said...
This comment has been removed by the author.
Alexander R Pruss said...

I don't see how this can happen "without the content of his knowledge changing". If a proposition wasn't true at a time t0<t* and was true at t*, then at t0, that proposition wasn't in the content of God's knowledge, and at t*, it was in the content of God's knowledge. This sure seems like a change in the content of God's knowledge.

Sean Killackey said...