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Welcome to Defenders, the teaching class of Dr. William Lane Craig. Today an excursus on Natural Theology, Part 24. For more resources from Dr. Craig, go
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to reasonablefaith.org Last time we introduced the concept of possible worlds in order to help us better understand the ontological argument for God's existence. And I emphasize that possible worlds are not any sort of concrete object, a planet or a universe. The easiest way to think about a possible world is just as a list of statements, a sort of massive conjunction. P and Q and R and S and so on. So that this massive conjunction includes every proposition or its opposite. And thus it yields a maximal description of reality. Nothing is left out. And that's what a possible world is. It's just sort of a maximal description of. Of reality. And reality could have been different ways. So different descriptions will make different possible worlds. For example, P and not Q and not R and S and so on. Or you could have. So we'll label that in W1, and this will be W2. Here's W3. That could be, say, not P and Q and R and not S and so on. W4. Yet another world could be not P and not Q and not R and S and so on. So that you have various descriptions of the way the world could have been and the description which has only true conjuncts, that is to say, the description, every conjunct of which is true, will be the description of the actual world. That will be the true description, that will be the actual world. And so what the ontological argument wants to do is to show that if God's existence is possible, if God exists in one possible world, then he exists in all of them. Now, last time Bob raised the idea that maybe these other worlds really aren't possible. Maybe there's only one possible world, and that's the actual world alone. I think that's a mistake. But suppose we, for the sake of argument, agree there is only the actual world. How would that affect the ontological argument? Would that mean that the ontological argument doesn't work if there's only one possible world? Well, in fact, if you think that there's only one possible world, what that really implies is that the ontological argument goes through with a vengeance. Why is that? Well, remember, the ontological argument wants to prove that if God exists in one possible world, then he exists in all of them. So if there is only one possible world, it follows immediately that if God's existence is possible, then it's actual, because that's the only world there is. The actual world. So far from invalidating the ontological argument, this view actually makes the ontological argument all that much easier. The challenge in the ontological argument for the person who thinks that there are lots of possibilities is how do you get from the fact that God exists in one possible but non actual world, like say W5, to existing in the actual world? That's a challenge. How do you get from God's existing in some possible but non actual world to the actual world? But if you think there is only one world, there's only the actual world, then that obstacle no longer presents itself, does it? Then the inference is immediate. If God's existence is possible, then God actually exists because there is only one possible world, namely the actual world. So I think that if you do hold to that view, the ideological argument should be very congenial to you and would be one that you would readily support. Now, when we talk about possible worlds, as I said in response to Brad last time, these various conjunctions need to be not only compossible, that is to say, they need to not only be possible together, but each one of them individually needs to be possible as well. For example, take the proposition the Prime Minister is a prime number. That proposition isn't even possibly true. The Prime Minister is a concrete object, a flesh and blood human being, and therefore it is impossible that he could have been a prime number. There's no way that a prime number could be the prime minister. And so that means that no possible world will include that statement as one of its conjuncts, because it's impossible. That will be false in every possible world. It's necessarily false. So a proposition which is necessarily false will be one that is false in every possible world. Now, by contrast, the proposition George McGovern is the president of the United States is false in the actual world. But there are possible worlds in which it's true. McGovern could have been elected President of the United States. And so that is a possible proposition, and it will be a conjunction in some possible worlds. So just to say that McGovern is the president of the United States in some possible world is simply to say that there's a maximal description of reality that has that relevant proposition as one of its conjuncts. Now, that isn't the actual world. That would be a non actual possible world, a possible world which isn't actual one in which that conjunct is true. And Leibniz's insight into the ontological argument is that the argument assumes that the proposition God exists, or a greatest conceivable being exists or a perfect being exists is possibly true. That is to say that God exists in some possible world. In some possible world, that statement that conjunct God exists, a maximally great being exists, a perfect being exists. That proposition is true. In some possible world, if the concept of God is incoherent or impossible, then God would be like that prime minister, that is a prime number. It would be a metaphysical impossibility. He would not exist in any possible world. The word God in that case, if the concept of God is incoherent would refer to nothing any more than the words a square circle refers to something. In both cases, the words a greatest conceivable being or a square circle would just be an incoherent combination of words. They don't refer to anything. So as Leibniz says, the ontological argument assumes that the concept of God is a coherent concept, that it's possible for God to exist. Now, in his version of the argument, Alvin Plantinga, whose version we are examining, Alvin Plantinga conceives of God as a being which is maximally excellent in every possible world. God is defined as a being which is maximally excellent in every possible world. Now what does he mean by that? Well, by maximal excellence, Planting it takes this to entail such excellent making properties as being, all knowing, all powerful, and all good. A being which has those properties will be more excellent than a being which is limited in knowledge or strength or goodness. And so a maximally excellent being will be one that has omnipotence, omniscience and moral perfection. A being which has maximal excellence in every possible world has what planning calls maximal greatness. So there's a difference between maximal greatness and maximal excellence. Maximal excellence is the property of being, all knowing, all powerful, all good. Maximal greatness is the property of having maximal excellence in every possible world. Now, Plantingus says the property of maximal greatness is possibly exemplified, that is to say, this is a coherent concept. There's a possible world in which a maximally great being exists. But if a maximally great being exists in every possible world, then if he exists in one possible world, he exists in all of them, including the actual world. And therefore God exists exists. Now, although Plantinga thinks that the ontological argument is a sound and non question begging argument for God's existence, initially at least, he did not regard it as a quote successful piece of natural theology, unquote. Why not? Why isn't this a successful piece of natural theology? Well, he said it's because the key premise of possibly maximal greatness is exemplified can be rationally denied. You can be rational and deny that maximal greatness is possibly exemplified. Or in other words, you can be rational and deny that it's possible that a maximally great being exists. But Plantinga later confessed that he had set the bar for quote unquote, success in natural theology unreasonably high. This is what he later came to I employed a traditional but wholly inappropriate or improper standard. I took it that these arguments are successful only if they start from propositions that compel assent from every honest and intelligent person and proceed majestically to their conclusion by way of forms of argument that can be rejected only on pain of insincerity or irrationality. Naturally enough, he says, I joined the contemporary chorus in holding that none of the traditional arguments was successful. I fail to note, he says, that no philosophical arguments of any consequence meet that standard. Hence the fact that theistic arguments do not is of less significance than I thought. So Planting says he initially thought to be a successful piece of natural theology, these arguments had to compel assent from any rational person, and he came to see that if you hold that standard, then there are no sound philosophical arguments for anything, or no good philosophical arguments for anything. Platting a now believes, and I quote, the ontological argument provides as good grounds for the existence of God as does any serious philosophical argument for any important philosophical conclusion. End quote George Mavrodis, who was a professor of philosophy at the University of Western Michigan, rightly remarked on planning his assessment. If natural theology can be that good, as good as the best arguments anywhere in serious philosophy, why should we not put forward these powerful arguments as proofs of God? End quote now we can formulate planning a version of the ontological argument as on your handout Step one. It is possible that a maximally great being exists, or in other words, maximal greatness is possibly exemplified. It's possible that a maximally great being exists. 2. If it's possible that a maximally great being exists, then a maximally great being exists in some possible world. 3. If a maximally great being exists in some possible world, then it exists in every possible world. For if a maximally great being exists in every possible world, then then it exists in the actual world. 5. If a maximally great being exists in the actual world, then a maximally great being exists, from which it follows therefore, a maximally great being exists. Now you might be surprised to learn that premises 2 through 5 of this argument are relatively uncontroversial. The real point of contention is premise one, that it's possible that a maximally great being exists. This is the principal question which needs to be settled with regard to planning as version of the ontological argument. What warrant exists for thinking that this key premise, it's possible that a maximally great being exists, is true? Now, in dealing with this issue, it's very important that we keep firmly in mind the difference between what we could call epistemic possibility and metaphysical possibility. Epistemic derives from the Greek word episteme, or knowledge, and epistemic possibility indicates what is possible with respect to your knowledge. So in response to the ontological argument's key premise, one is tempted to say, well, it's possible that God exists, and it's possible that God does not exist. And that is true only with respect to epistemic possibility. What you're saying there is, for all I know, God exists or he doesn't exist. It's possible. With respect to what I know, it's epistemically possible. I don't know which is right. For all I know, God may or may not exist. But if God is a maximally great being, then his existence, if it's metaphysically possible, it will be metaphysically necessary. This type of possibility has to do with what is actualizable or what is real independently of what you think about it. And in God's case, his existence is going to be either necessary or impossible. It can't be merely contingent. It will not be true to say, well, it's possible that God exists or it's possible that he doesn't. That that would be to say God exists in some possible worlds, but he doesn't exist in other possible worlds. And that would be metaphysically incorrect. The concept of a maximally great being is such that it either exists in all possible worlds or it exists in none of them. But you can't say it exists in some of them and it does not exist in others of them. Let me give an illustration of this difference between epistemic possibility and metaphysical possibility that will help to make the point clear. There is a metaphysical or there's a mathematical proposition known as Goldbach's Conjecture that remains unproven in mathematics today. Goldbach's Conjecture says that every even number greater than two can be expressed as the sum of two prime numbers. So take any even number greater than two, any even number greater than two that will be equal to the sum of two prime numbers. And although Goldbach's Conjecture has been tested to enormous lengths, no mathematician has ever been able to prove it or disprove it. We don't know whether Goldbach's conjecture is true or not. And so in this epistemic sense, one can say epistemically. Well, Goldbach's conjecture could be true or it could be false, we just don't know which. But as a piece of mathematics, you see, Goldbach's conjecture is either necessarily true or necessarily false. So that it is either necessary that Goldbach's conjecture is true, or it's impossible that it's true. It cannot possibly be true and possibly be false. In this metaphysical sense, it is either impossible or necessary, one or the other, but cannot be both possibly true and possibly false. It's necessarily true or necessarily false. And in the same way, although the key premise of the ontological argument could be epistemically uncertain, we don't know whether it's possible that a maximally great being exists or not. Nevertheless, the epistemic entertainability of the key premise, or of the denial of the key premise doesn't guarantee that it's metaphysically possible. So the question we're asking here is, is it metaphysically possible that a maximally great being exists? Not is it epistemically possible? Which it I think certainly is. But is it metaphysically possible? Well, think about it. The concept of a maximally great being being seems, intuitively speaking, a coherent idea and therefore possibly instantiated. The idea of a being which is all knowing, all powerful, all good, in every possible world seems to be a perfectly coherent idea and therefore possibly instantiated. In order for the ontological argument to fail, the concept of a maximally great being would have to be logically incoherent. It would need to be like the concept of a married bachelor. The concept of a married bachelor, when you think about it, is not a strictly or explicitly self contradictory concept, as would be, say, the concept of a married unmarried man. That would be strictly contradictory, a married unmarried man. But nevertheless, once you understand the concept or the meaning of what a bachelor is, you can see that it's impossible that there could be something corresponding to that concept, that that concept could be possibly exemplified, or that property possibly instantiated. And by contrast to that, the concept of a maximally great being doesn't seem at all incoherent. Quite the contrary, it seems perfectly coherent to talk about a being which is maximally excellent in every possible world. And that would go some distance, I think, to warrant the first premise that it's possible that a maximally great being exists. Now, some of you might be thinking, well, but doesn't this lead to a kind of Ontological overkill. One of the most important strategies that detractors of the ontological argument adopt is to provide parodies of the ontological argument that would lead to all sorts of absurdities that nobody would think exists. And these go back to Anselm's fellow monk, Guanillo. You remember Anselm was asking the question, why does the Scripture say the fool hath said in his heart there is no God? Why does the scripture call the atheist a fool? And Anselm's answer to that was, well, because once you properly understand the concept or the word God, you can see that God must exist, and therefore the fool is saying something incoherent in saying God does not exist. Well, Guanillo, his fellow monk, wrote a treatise called On Behalf of the fool in which he criticized Anselm's argument. And the way he did so was to construct parodies of the argument where you would try to construct parallel ontological arguments for absurd conclusions. For example, it's been suggested that you could prove that a most perfect island exists in this way by saying a most perfect island must have all of these properties in every possible world, and that's possible. Therefore, a most perfect island actually exists, or a necessarily existent lion. A lion that has the property of necessary existence would exist in every possible world, and therefore there must be a necessarily existent lion. Those seem to be coherent concepts, and yet they would lead to the postulation of entities which nobody would accept. In my debates on the existence of God, some of my opponents have suggested, for example, the idea of a necessarily existent pizza or a most perfect pizza would be one that exists in every possible world. And therefore, if the ontological argument is sound, we should believe in the existence of the most perfect pizza or necessarily existent pizza. Now, what might the defender of the ontological argument say in response to these parodies? Well, quite a bit, I think. I think that the proponent of the ontological argument can plausibly claim that the concept of God differs from these supposedly parallel concepts, like a most perfect island or a necessarily existent lion, or necessarily existent pizza, for one thing. Firstly, the properties that go to make up maximal excellence that Plantinga talks about have intrinsic maximum values. For example, omniscience is the property of knowing only and all truth. You can't get any more knowing than that if you know all the truths there are. So there's an intrinsic inherent ceiling on this property of omniscience. Similarly for the other properties like moral perfection and omnipotence. But that's not the case with things like islands Islands don't have sort of intrinsic maximal properties, as planting says, there could all be be more palm trees and native dancing girls to improve the island. So it really is an incoherent concept to talk about a most perfect island in a way that isn't incoherent to talk about a maximally great being. Secondly, it's far from clear that there really are objective excellent making properties of things like islands. Are there really objective properties that go to make up the excellence of islands? Well, it seems not. That's a very subjective thing dependent upon your personal preference. Do you prefer a desert island or one that is crowded with the finest resort hotels? Well, it depends on your tastes. Which one of these you think is the better island? Right. So there really aren't these sort of objective excellent making properties that go into islands in the way that omniscience, omnipotence and goodness seem to be objective great making properties. So with respect to the parity of the island, there are two problems. The lack of intrinsic maximum value the and then the lack of the objectivity of there even being excellent making properties of islands. As for the idea of something like a necessarily existent lion or a necessarily existent pizza, this also, when you think about it, I think, is incoherent. For as a necessary being, such an animal would have to exist in in every possible world that we can conceive. But any animal which would exist in a possible world in which the universe is comprised of a single infinitely dense space time singularity, just is not a lion. That is not what you mean by a lion. Similarly, it's not a pizza either. By contrast, a maximally excellent being could be immaterial and therefore transcend the physical limitations of space and time, and so could be necessarily existent. It could exist in a possible world in which the universe is a space time singularity. And lest you think that that a pizza, say, could be immaterial, that wouldn't be very satisfying, would, wouldn't satisfy your appetite. A pizza is something that you can eat and you can't eat an immaterial object. So again, the idea of a necessarily existing pizza, a necessarily existent lion, upon closer reflection, really does turn out to be incoherent and therefore doesn't exist in other possible worlds. Now, perhaps the greatest challenge to the appeal to our intuitions to justify premise one, and by appeal to intuition, what I mean is that it just seems clear that it's possible that maximal greatness is exemplified. This looks coherent to us. This looks like a coherent idea, and therefore one that is possibly exemplified. The greatest challenge to that appeal, I think, would be to say that it is intuitively coherent in exactly the same way to conceive of what we might call a quasi maximally great being, that is, say, a being with which is in every other respect maximally excellent, except that in one of those excellent making properties it's a little deficient. For example, imagine a being which is morally perfect, omnipotent, but it's not quite omniscient. It doesn't know future contingents. It's the God of open theism who knows all past and present propositions, but he doesn't know the truth value of future tense propositions about contingent events. Why is the premise of the ontological argument more plausible than a parallel argument that says it's possible that a quasi maximally great being exists? If we're warranted in thinking that a maximally great being exists, wouldn't we be equally warranted in thinking that it's possible that a quasi maximally great being exists? And if you think that, then you've got to think that such a being does exist. It wouldn't deny the existence of God per se, but it would mean that in addition to the maximally great being, you're going to populate your world with all sorts of quasi maximally great beings. And that would surely be implausible and undesirable. So if the key premise of the ontological argument is possible or is true, isn't it also true that it's possible that a quasi maximally great being exists? Well, I'm not so sure. I think not. Because maximal greatness, I want to argue, is logically incompatible with quasi maximal greatness. Think about it. A maximally great being is by definition an omnipotent being. It's all powerful. That's part of what goes to make up maximal greatness. So no concrete object could exist in independently of its creative power as an omnipotent being, a maximally great being would have to have the power to freely refrain from creating anything at all. And therefore there must be possible worlds in which nothing but the maximally great being exists. But that entails that if maximal greatness is possibly exemplified, then quasi maximal greatness is not. Now, there might be quasi excellent beings in many worlds, worlds in which the maximally great being has chosen to create quasi excellent beings. Maybe they would be like angels, that would be supernatural, superhuman, but not like God. But those beings would lack necessary existence. They would be created by the maximally great being, and therefore they would not be quasi maximally great. They could be quasi excellent, but they wouldn't be quasi maximally great because they wouldn't exist in every possible world. So if maximal greatness is possibly exemplified, which I think is intuitive, that means that quasi maximal greatness actually turns out to be impossible. Because a quasi maximally great being would be a being that has necessary existence and therefore would exist in every possible world. He would be outside the omnipotent power of the maximally great being. So our intuition that a maximally great being is possible possible is not undermined by the claim that a quasi maximally great being is also intuitively possible, because the latter intuition, the intuition that quasi maximal greatness is exemplified, depends upon the assumption that a maximally great being cannot possibly exist. And that would beg the question, so long as maximal greatness is possible, then it would follow that quasi maximal greatness is not. Now still, skeptics might insist that we don't have any way of knowing a priori or in advance whether it's maximal greatness or quasimaximal greatness, which is possibly exemplified. The argument that I've just given shows that it can't be both. You can't have both, both a maximally great being and a quasi maximally great being. They would be incompatible with each other because one would escape the omnipotence of the other. So you can't have both. But the skeptic might say, we don't know if either one is possible. Our intuitions about modality are unreliable guides. Now, I do think we can say here that the intuition that a maximally great being exists trumps any intuition that we might have that quasi maximal greatness is possibly exemplified. You only arrive at the idea of quasimaximal greatness by subtracting something from the concept of maximal greatness. And so, in a sense, it's parasitic on the concept of maximal greatness. So if quasimaximal greatness seems possible, all the more so maximal greatness would seem possible. And that would give reason, then for thinking that priority should be given to maximal greatness and not quasi maximal greatness. But could we say anything more in defense of the ontological argument's key premise? Can we say something more than just modal intuitions, that it seems intuitive that this is a coherent concept? Well, planting, I think, provides a clue when he says that if we carefully ponder the key premise and the alleged objections to it, if we, quote, consider its connection with other propositions we accept or reject, and we still find it compelling, than we are within our rational rights in accepting it. Now, that's a far different story than the sort of a priori speculation that the skeptic denounces, even if you cannot determine a priori, that is, say, in advance whether or not maximal greatness is possibly exemplified. What planning is suggesting is that we could come to believe that it's possible that a maximally great being exists on the basis of a posteriori considerations, that is to say, on the basis of evidence and argument, independent of our modal intuitions. And so what I want to do next time is to look at some of those considerations that might lend support to our modal intuitions that maximal greatness is indeed a coherent concept. And if that's the case, then the basis for affirming premise one will not simply be our modal intuitions that this is a coherent concept or idea, but that we also have some extra additional reasons for thinking that premise one is true. All right, well, that brings us to the end of our time. We'll have time for discussion of these considerations before we begin our next class. Next week, David Sherrill is going to be teaching for me as I'll be out at Arizona State University. And so I think that should be very interesting as we always appreciate the things David has to share. Well, let's end with a word of prayer. Father, thank you for the opportunity to have been together this morning and to consider these things. We pray, Lord, as we think about them and reflect on them, that you would increase our understanding of your greatness and who you are. And so repose more confidence in your sovereign direction in our lives throughout the week. In Christ's name we pray. Amen.
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The copyright for the content of this recording is held by Dr. William Lane Craig. For more go to reasonablefaith.org.