William Lane Craig CV


Existence of God (part 24)

Transcript of William Lane Craig's Defenders 2 class.

Excursus: Natural Theology
§ V. Ontological Argument
Lecture 2

We have been talking about the Ontological Argument. It basically shows that if it is possible that God exists, then it follows that God exists. So the principal issue that needs to be settled with respect to this argument is the first premise – that it is possible that a maximally great being exists. The other steps of the argument are relatively uncontroversial. The really controversial premise is – is it possible that God exists?

The Argument Examined

Epistemic vs. Metaphysical Possibility

In dealing with this issue we need to keep in mind the difference between what we could call epistemic possibility and metaphysical possibility. What do I mean by those terms? Epistemic possibility just means “for all we know, something is possible.” Take some complicated mathematical equation that we might write out on the blackboard – say, the square root of 176 is 14 or something like that. We might say, for all we know, that might be true. But if it is true, it is necessarily true, whereas if it is false, it is necessarily false. Mathematical equations are either necessarily true or they are impossible. But epistemically, that is to say, as far as we know, it is possible. We look at that and say it is possible that it is true, and it is possible that it is false. That is correct to say in an epistemic sense. But in a metaphysical sense, it cannot really be false if it is true, and it can’t be true if it is false. Metaphysical possibility and necessity would mean the way something can actually be. Can something actually be that way or is it actually impossible?

With respect to this first premise, we should resist the temptation to say, “Well, it is possible that God exists or it is possible that he doesn’t exist!” That is true epistemically. “For all we know, it is possible that God exists or doesn’t exist!” But, if a maximally great being exists, he exists necessarily in this metaphysical sense. Therefore, God’s existence is either possible or impossible. So the atheist has to maintain that God’s existence is metaphysically impossible in order to avoid this argument, whereas the defender of this argument thinks that God’s existence is not merely epistemically possible (“for all we know he exists”), rather he thinks that God is metaphysically possible as well.

Coherence of a Maximally Great Being

So the question is, do we have any reason to think that the existence of God, a maximally great being, is metaphysically possible, as opposed to just epistemically possible? Is there any reason to think this first premise is true in a metaphysical sense of possibility? I think there is reason for that. Intuitively, the idea of a maximally great being is a coherent idea. When you think about the notion of a being that is all-powerful, all-knowing, and all-good in every logically possible world, that seems to be a perfectly coherent idea. In order for the Ontological Argument to fail, the concept of God needs to be metaphysically impossible. It needs to be logically incoherent, like the idea of a married bachelor or a round triangle. Those things clearly are metaphysically impossible because they are incoherent. But when you think about the idea of a maximally great being, there is nothing in that concept that appears to be even remotely incoherent. Indeed, I think we have a positive grasp of that concept as a coherent idea. If that is correct, that provides some intuitive basis for thinking that this first premise is true, that it is possible that a maximally great being exists.1

Parodies of the Argument

One of the main reasons that is often given for doubting the first premise of the Ontological Argument – and this is a very ancient strategy – is that if this type of reasoning is correct, then we ought to be able to think up parodies of the argument – thinking of other sorts of things that would then have to exist. For example, the idea of a most perfect island would be one that exists in every logically possible world and has all of the great-making properties that make up a perfect island, and therefore there must exist something like this. Or the concept of a necessarily existing lion would be the concept of a lion that exists in every possible world, and so therefore a necessarily existent lion must exist. These notions must also seem coherent, and therefore, if it is possible there is a necessarily existent lion, then there must be one. Or if it’s possible that there is a maximally great island, then there must be one. But this is absurd.

The argument’s proponent can defend his argument against these sort of parodies by arguing that these supposedly parallel notions aren’t really analogous to the idea of a maximally great being. For one thing, the properties that go to make up maximal greatness have intrinsic maximal values. Things like being all-knowing means knowing all truth. There is a kind of maximum quality there that you can’t get beyond – you know all truth. Being omnipotent is being able to do anything that is logically possible. Or being all-good. These have intrinsic maximal values. By contrast, something like a most perfect island or a maximally great island doesn’t seem to have those kind of intrinsic great-making properties. In the case of islands, for example, there could always be more palm trees and more hula girls to increase the greatness of the island. It is not even obvious what the intrinsic properties of a greatest possible island would be. That seems relative to your interests. You can think a great island is a remote desert island where you can be by yourself or is one that is bursting with fine resort hotels and all sorts of entertainment. It is relative to the interests of the vacationer. The idea of a greatest island or a most perfect island really turns out not to be a coherent idea. There aren’t intrinsic maximal values or even objective properties that go to make up the excellence of islands.

The idea of a necessarily existent lion, as well, is also incoherent. Just think about it. In order to be such an animal, this beast would have to exist in every logically possible world. But that would mean that in a world in which the universe consisted of nothing but a singularity, just a point of infinite spacetime density, pressure, curvature, that there would be this necessarily existent lion. Anything that could exist in a universe which consisted of a simple singularity just isn’t what we mean by a lion. A lion is a sort of big cat having certain properties, and it couldn’t exist in a universe like that. So, clearly, a lion is subject to certain sorts of physical limitations in order to be a lion and therefore cannot be coherently conceived to be necessarily existent.

This can become almost ludicrous at times. In my debate with Victor Stenger at Oregon State University, in response to the Ontological Argument, he attempted to parody the argument by saying maybe there is a maximally great pizza, the greatest possible pizza, and therefore that would have to exist as well. And what I pointed out was the greatest possible pizza would have to exist in every logically possible world and that would mean that it couldn’t be eaten! Right? Because it is metaphysically necessary. Therefore, it would not be a pizza because a pizza is something you can eat. Again, it just turns out these parodies are often incoherent ideas that don’t really match the intuitively coherent notion of a maximally great being, one that is all-powerful, all-knowing, and all-good in every logically possible world.2


Question: Are there arguments or disagreements on what God’s characteristics must be? God has certain characteristics (omnipotence, omniscience, aseity, etc.) and if God exists and necessarily has those characteristics, then that would imply that we would all need to agree with that he has those characteristics or else that would not be the maximally great being. Is he simple, for instance? Would someone who wants to argue against the Ontological Argument say that a maximally great being might not have some characteristics that we think God has?

Answer: You are absolutely right that there is dispute in this case as well as to what makes for a great-making property in God’s case. That is why Plantinga cashed the argument out in relatively uncontroversial properties like being all-powerful, all-good, and all-knowing. But he doesn’t say, for example, that the greatest conceivable being would be timeless rather than temporal or simple rather than complex. It is certainly true that some of those properties are less intuitively clear in terms of whether they are really great-making properties. Is a being that exists timelessly greater than one that exists temporally? I think that is far from obvious. So that is why the argument is couched simply in terms of these three properties. If there is such a being, then we need to examine further whether or not we have any reasons to think that this being is temporal or timeless, simple or complex. Has he revealed himself in the world or has he not? Those can be issues, then, that can be further explored or maybe even known on the basis of divine revelation. Those would still be in some cases perhaps necessary attributes of God, but it is just that we wouldn’t have any clear intuitions about that. So the argument is couched simply in terms of those that are pretty indisputable as being great-making properties, and we leave it an open question as to what other properties this being has.

Question: I can’t share your enthusiasm for this argument. I am going to have to reject premise one on what I consider contradictory attributes. Let me first say Dr. Plantinga has defined himself to victory by saying this maximally great being exists in all possible worlds. This is of course a possible world, so by definition here he is, and there is really no debate. Similarly, I have a problem with this logically possible worlds argument anyway, because I don’t believe there is any world that is logically possible other than the one that we have.

Answer: I don’t think you really believe that. There has to be a misunderstanding. You don’t think that everything that happens happens logically necessarily – that you have no free will, for example, that it would be logically impossible for you to lower your hand right now.

Followup: Maybe we have different ideas of what a possible world is. I am saying from my understanding of this possible worlds idea is any world that you can conceive of this being would have to exist in. I don’t believe there can be another world besides what we have. The world that we have has various turns and different futures, but how can there be another universe or reality other than the one that we have?

Answer: Let’s answer that question by your choosing to do something different. In this world, you will get up and go to lunch in a few minutes. But you have freedom of the will, I believe, and you could choose instead to just remain seated. And then a different world would exist than the one that will in fact exist.

Followup: I would say that is the same world. We all have different choices within the same world.

Answer: It is not the same world in the sense that different events occur and so, if a world is simply a description of the way reality is, those are not the same description. They have different events in them and so they are different descriptions, and that is all a “world” means here – a maximum description of reality.3

Followup: Maybe I am not looking at it quite the way you do. But I believe there are contradictory attributes in Plantinga’s maximally great being. First, he says he is maximally great and therefore maximally good. Then he says he exists in all possible worlds. I don’t think those two things go together. If you have a maximally great being, there is no way he is going to exist in but a very small minority of all the worlds that we can conjure up because they would be abhorrent to him.

Answer: This is a very good point that you are making here. A very good point! Intuitively, we would think that it is logically possible that there would be a world in which there would be no higher life forms than, say, rabbits who are diseased and sick and exist in a state of continual pain and suffering. That seems to be logically possible. But I think you are quite right in saying God would never permit such a world. He is too good and wouldn’t create such a world. So what that means is, if God does exist, that envisioned world of animal pain and suffering isn’t really logically possible at all. What is implied here is that if you believe in God as a metaphysically necessary being, this is going to radically affect your view of what is possible or impossible. Certain things that look as if they are possible turn out really not possible at all. Another example would be a world in which every human being rejects Christ and goes to hell. I think that is incompatible with the goodness of God – God would not create such a thing. What this means is that isn’t really a possible world. That really is a logically impossible or incoherent state of affairs. You are quite right in your intuition here that certain sorts of states of affairs are going to be incompatible with God and his existence. But I think most Christian philosophers would do, rather than deny that God is metaphysically necessary (which would make God a contingent being, and we don’t want to say that), is prefer to revise their view of possible worlds. They would do that rather than revise their concept of God as being metaphysically necessary and all good. You have got to revise something, and I think most of us would say you revise your concept of what is really logically possible rather than revise the concept of God, so that he is no longer the greatest conceivable being. This is a very thought provoking question.

Question: I am also not enthusiastic about this argument either. How do you rhetorically get around the idea that somebody feels that you are loading the dice in your favor from the get-go? In a debate, it looks like in this argument you are saying, “If you can even conceive of God, I win.”

Answer: I think the way you do it is by making this distinction between epistemic and metaphysical possibility. And to affirm that something is metaphysically possible is making a significant truth claim. It would not be significant if we were just talking about epistemic possibility. In that case, you are just saying, “Well, yeah, for all we know he exists or he doesn’t exist!” But you are making a significant claim here. You are saying it is logically possible that there be a maximally great being having this description of these properties. That is a significant truth claim, to say that that is coherent. But then if you admit it is possible, then the rest just follows.

Followup: So you don’t have an issue at all with building on a metaphysical pragmatism just constructing an ontology of God by way of . . .

Answer: Why do you call it pragmatism?

Followup: Because of what you are forced to do by way of your mental or noetic faculties.

Answer: I don’t have any problem with that at all. There is nothing circular about this argument because you are not saying that you believe premise (1) is true because you believe that God exists.4 That would be circular. You are saying, “As I think about this idea of a being that is all-powerful, all-good and all-knowing in every possible world, that is an intuitively coherent idea. It is not like a married bachelor or a necessarily existent lion or a maximally great pizza – which are all incoherent. This is a coherent idea and therefore something that possibly exists.” That is a significant truth claim to say that such a thing is possible; but what follows from that is: if it is possible, then it is necessary. Like that mathematical equation – if it is possibly true, it is necessarily true.

Let me put it this way (and this is how I presented it in the debate): at the very least what the argument shows is that if God’s existence is possible, then God must exist. That is a conditional claim. You don’t have to defend that it is possible that God exists – just leave that up to your audience. That is what I did in the debate. I didn’t try to prove that it is possible that a maximally great being exists. All the argument shows is that if it is possible, then God must exist. So what do you think? Do you think it is possible that God exists, as I do? Then you should agree that God exists. If you do not think that God exists, then you have got to say that the concept of God is logically incoherent. You have to affirm that it is impossible. Not just that he doesn’t exist but that he is impossible to exist. So the conditional statement of that argument is still very powerful. If it is possible God exists, if the first premise is true, then God exists. That in itself is an important insight.5


1 4:53

2 10:02

3 15:12

4 20:02

5 Total Running Time: 22:07