Is This a Good Argument for Atheism?

Kevin Harris: Hey, it's Kevin Harris. Before we get into today's podcast, I want to let you know about something really special that we're doing this month at Reasonable Faith. Spoiler alert, it's free! We've put together a brand new resource called the Daily Defender. It's a 31-day reader based on Dr. Craig's Defenders class. Each day provides a Scripture, walks you through a short reading about who God is, his attributes, his greatness, his love, and it ends with a short prayer for reflection. Now, I don't know about you, but personally I have found that resources like this really keep me on track in the spiritual disciplines and my personal walk with God. There are so many distractions in our lives. That's why prayer apps and things like that have become very popular. So we're really excited about the Daily Defender because you not only get that extra boost in your daily prayer and study, but you get the benefits of Dr. Craig's lifelong work in ministry. It will strengthen your faith and your understanding of God one day at a time. Download the Daily Defender for free at ReasonableFaith.org/dailydefender and follow along with thousands of others throughout this month and even beyond. It's our way of saying thank you and giving back to the community during our fall matching grant campaign, which is going on now, by the way, and is fast coming to an end. Dr. Craig has more on that at the end of the podcast. We hope you'll join us in reading the Daily Defender this month. Download it from the website. Now, let's go to the studio with Dr. Craig.

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Kevin Harris: Well, Bill, I must be a glutton for punishment wanting to talk about the ontological argument. I'm fascinated by this argument, as a lot of people are. And if any of our listeners are not familiar with it, you're going to find out just how fascinating it is. We're going to take a look at a new ontological argument for atheism from Joe Schmid, who is a doctoral student in philosophy at Princeton, and a couple of his colleagues. They published a paper on this argument, and we have some clips from an interview with him. Now, Bill, sometimes people ask if you've ever changed your mind on an argument or a theological view, and you've replied that the ontological argument is an example of that. What changed?

Dr. Craig: Well, I became convinced that the argument was not simply valid, but that it was sound – that the premises of the argument are true and that there are good grounds for believing the premises to be true. After being skeptical of the ontological argument for many years, I came to believe that this is a sound argument for God's existence.

Kevin Harris: And we'll define it a little further as we go, so everybody hang with us. Now, here's the first clip from Joe in a YouTube interview^[1] with Phil Halper. Joe gives a brief overview of the ontological argument. Clip number one.

Joe Schmid: So, ontological arguments are really a family of arguments for God's existence. They all seek to show that God exists purely from the armchair, or purely a priori, as philosophers say. That just means that their premises are supposed to be justified independently of sensory experience. They typically try to derive God's existence from reflecting on the concept of God, or the nature of God, or the nature of perfection, or stuff like that.

Kevin Harris: So there's not just one ontological argument, Bill. There's a family, and it's a reflection from the armchair. I suppose that it's something that you can sit on your couch and work through. Expand on his comments.

Dr. Craig: Well, this is the traditional understanding of the ontological argument, and I too used to think that it was a purely a priori argument, but I've changed my mind about that. I think that we can give evidence a posteriori—experiential evidence—in support of the key premise that it's possible that God exists. For example, let me share with you what Josh Rasmussen calls the value argument in support of the key premise of the ontological argument. It's very simple, and it goes like this.

1. Some degree of value can be instantiated. We know that from moral experience. We experience moral value. And if moral value actually is instantiated, then it follows that some degree of value can be instantiated.
2. If some degree of value can be instantiated, then each degree of value can be instantiated. There's nothing about grades of value that would make some possible and some impossible. So if some degree of value can be instantiated, then each degree could be instantiated.
3. Therefore, each degree of value can be instantiated.
4. Maximal greatness is a degree of value. That seems intuitively right. It's the supreme value, the greatest degree of value there could be. From which it follows...
5. Therefore maximal greatness can be instantiated. That is to say, it's possible that maximal greatness obtains – is instantiated. And that is the key premise of the argument.

So I think this is a remarkable argument that Rasmussen gives in support of the key premise of the ontological argument. Rather than say that the ontological argument is an a priori argument, I think perhaps it's better to characterize the argument by saying that it's an argument that holds that if it's possible that God exists, then God exists.

Kevin Harris: By the way, we'll put a link to the paper if you want to check out Joe's paper. It's free, and you can read it. Next, he gives a more detailed definition of the ontological argument for God. Clip number two.

Joe Schmid: Now, you asked about the original version. I think it's typically credited to Anselm, but I wouldn't be surprised if people pinpointed it in Augustine or even others before him, but typically it's credited to Anselm.

Kevin Harris: Let's stop right there. Bill, is Anselm most often credited with this argument?

Dr. Craig: Yes, and properly so. Anselm is the originator of the argument, and it is found in his treatise Proslogion, written in the year 1078.

Kevin Harris: Let's continue the definition, clip number three.

Joe Schmid: Now, the simplified version of the modal ontological argument that I tend to give to people on the airplane: the first premise is that God possibly exists. The second premise is that God's existence is either impossible or necessary. And from those two premises, it follows that God necessarily exists and hence he exists. Because if God's existence is either impossible or necessary, and as the first premise says, it's possible, then it's not impossible, so it must be necessary. And if God's existence is necessary, then he must exist. But here's the more rigorous and precise canonical version of the argument. The first premise is that necessarily, if God exists, then it's necessary that God exists. The second premise says possibly God exists. And the conclusion that's supposed to follow from those, at least in certain systems of modal logic, is that God exists. Think of that first premise as saying that in any possible world in which God exists, God is a necessary being in that world. It belongs to the very nature of God that he's a necessary being. So for any world in which there's a God, go to that world, God's a necessary being. The second premise then says that there is some possible world in which God exists, and from those it follows that there's some possible world in which a necessary being exists, and in which that necessary being is God. So from those it follows that it's possibly necessary that God exists, because there's some possible world in which a necessarily existent God is real.

Kevin Harris: Well, what do you think about his more detailed definition, Bill?

Dr. Craig: I think that my formulation of the ontological argument is much clearer than Joe's. They amount to the same thing, but I think that most of our listeners would find his formulation unnecessarily difficult to follow. Here's my formulation of the argument that I think is clearer. Premise one: It's possible that a maximally great being exists; that is to say, it's possible that God exists. Two: If it's possible that a maximally great being exists, then a maximally great being exists in some possible world. Three: If a maximally great being exists in some possible world, then it exists in every possible world. Four: If a maximally great being exists in every possible world, then it exists in the actual world. Five: If a maximally great being exists in the actual world, then a maximally great being exists. Six: Therefore a maximally great being exists. Seven: Therefore God exists.

Kevin Harris: Is that basically the argument that's in Philosophical Foundations for a Christian Worldview?

Dr. Craig: As I recall, yes. This is basically Alvin Plantinga's version of the ontological argument simplified to make it more accessible.

Kevin Harris: Up next, Joe begins to distinguish what philosophers mean by modal logic. This is something that many may not be familiar with, so we'll talk about it. Here's clip number four.

Joe Schmid: A little bit of context: philosophers more recently have kind of distanced themselves from Anselm's version of the ontological argument, mainly because notions of conceivability—at least the ones he employed—are a little bit slippery. It's a lot easier to work with notions of possibility and the kind of formal systems that we've recently developed to think very rigorously and logically about modality. Modality just concerns possibility, necessity, and impossibility. So those are all modal distinctions, or distinctions in the mode or way in which something could be true or perhaps exist.

Kevin Harris: Well, just when I thought I was getting the basic laws of logic down, I started hearing about modal logic. Is there a difference between modal logic and regular logic, Bill?

Dr. Craig: Yes, indeed. Our regular non-modal logic doesn't deal with propositions that are possible or necessary or impossible. So a special modal logic has to be developed in order to deal with propositions of that sort.

Kevin Harris: Before we get to this ontological argument for atheism, I think it'd be helpful to define what is meant by symmetrical arguments. From what I understand, one can look at an argument and try to use the same premises to come to an opposite conclusion. To make an argument stronger, we must break the symmetry to show which argument is superior. Am I on the right track?

Dr. Craig: Well, no. I don't think so. Think about it. If you use the same premises, then it's the same argument and yields the same conclusion. Rather, you change a key premise while leaving the other premises the same. For example, in my argument, you would replace premise one—that it's possible that a maximally great being exists—with a different premise—it's possible that a maximally great being does not exist. And then you would run your bizarro ontological argument for atheism.

Kevin Harris: Okay. So here Joe outlines the ontological argument for atheism in this next clip. Here's clip number five.

Joe Schmid: Here's the airplane version of the reverse modal ontological argument for atheism. God possibly doesn't exist—that's the first premise. The second premise is the exact same as the original modal ontological argument’s second premise, namely, God's existence is either impossible or it's necessary. And from those it follows that God's existence is impossible, and hence God doesn't exist. Because if God possibly doesn't exist, that's to say that God's existence is not necessary. And given the second premise—that God's existence is either impossible or necessary—and it's not necessary, it follows that God's existence is impossible, and hence God doesn't exist. So that's the airplane version. But remember, I gave a more precise formulation, which makes clear the relevant contentions about God's nature, etc. Again, it has the same first premise, what we can call the necessity premise, which basically says that in any world in which God exists, God's a necessary being. More precisely, it is necessarily the case that if God exists, then it's necessary that God exists. The second premise then says possibly God doesn't exist, which is just like the second premise of the original modal ontological argument that possibly God does exist. And from those two premises it follows that God doesn't exist, at least in the standard systems of modal logic that defenders of the original modal argument use to validate their argument. In other words, they tend to operate in certain logical systems which make their argument valid, and in those same systems, this reverse argument is valid.

Kevin Harris: One of the first things we usually look for when somebody critiques the ontological argument for God is whether they're presenting a parody of the argument. I couldn't detect that here. What do you think about the reverse ontological argument that he sketched out, Bill?

Dr. Craig: Well, it's not a parody of the ontological argument. As I explained a moment ago, it's just a denial of the first premise. And so our listeners need to decide, with respect to this argument, which is more plausibly true: that it's possible that God exists, or that it's possible that God does not exist. If it's possible that God exists, then he exists necessarily. If it's possible that God does not exist, then God necessarily does not exist. So you can't say, “Well, I'm agnostic; it's possible that he exists, and it's possible that he doesn't exist.” That's true only in an epistemic sense—you don't know which one of those is true. But nevertheless whichever one is true is necessarily true. So you've got to decide: do you think it's possible that God exists, or do you think it's impossible that God exists? The atheist has to maintain not simply that God does not exist—the atheist has to maintain that it's impossible that God exists. And I think that my version of the argument, as well as the reverse argument, is much clearer than Joe's.

Kevin Harris: I tried to synopsize a very complicated paper from Joe Schmid in this interview, and when considering this as a topic for a podcast, I started learning a little about stronger versus weaker forms of modal logic. Bill, you're still going to have to hold my hand here. My understanding is that one can add more axioms to a logical system to make it stronger, or use less axioms to make it weaker. And weaker is preferred because it uses less controversial axioms. The more axioms that you add to the whole formula, the more controversial the whole system becomes. So am I close on this?

Dr. Craig: No. That would be a mistake to think that the axiom system with fewer axioms is less controversial and that the more axioms a system includes, the more controversial the whole system. That's just completely wrong. You need to understand, Kevin, that these axiom systems are just uninterpreted formulas that have no meaning. They are just marks on paper, and therefore they cannot be controversial because they're meaningless. They only become meaningful when you add semantics to these uninterpreted modal systems. Then the question that you must ask is: which modal system, when interpreted, yields a logic that enables us to make the inferences that we intuitively want to make? And by far the axiomatic system called S5 is preferred as best capturing our modal intuitions, and therefore is the preferred modal axiomatic system that will be used in, for example, metaphysics.

Kevin Harris: So the upshot is that Schmid and company argue in this paper that the weaker modal logic systems—and S5 is one example—actually favor the atheistic version. At least that's what they're claiming. Check out clip number six.

Joe Schmid: There is a logical asymmetry between the reverse modal ontological argument and the original. The reverse argument for atheism just requires KT, and that's extremely uncontroversial. The original modal ontological argument requires a logic which is more controversial, and so there is a decided advantage in favor of the reverse modal ontological argument. And that is just the core of our paper, I mean that’s it distilled into like two sentences.

Kevin Harris: He mentioned a logic system there called KT in that clip, Bill. And there are various modal systems with names like T and KT and KT4 and S5 and so on. You can add these axioms to the modal system. Joe says the reverse ontological argument only requires KT, for example, but the original ontological argument for God requires not only KT but additional axioms to work. Therefore, the reverse ontological argument is less controversial and is to be preferred. Is that what you're getting from that clip?

Dr. Craig: Well, if that is what he's saying, then I think the argument is fundamentally misconceived. If his argument depends on rejecting S5 as the preferred modal system, then his argument is hopeless, because it would mean we're dependent just upon the inferences that KT would permit. That would be far too emaciated a modal logic to enable us to draw the kinds of inferences that we want to. So that kind of anorexic modal system would just be hopeless. Now, if he says, “Oh, no, no, I'm not denying S5. I still will accept those axioms, but I just don't use them,” then what that implies is that the ontological argument is valid. You can get K systems that he refers to by adding axioms to the system called S4, but these K systems are not even included in S5. They are not a subset of S5; they are independent modal systems. So is that what the reverse ontological argument requires—not a weaker system, but a different one? Well, if that's the case, then again, it's just hopeless, I think. Now, I want to say as well that in a sense all of this is really beside the point. The question in assessing the ontological argument or its reverse is not which modal axiomatic system is best. Rather, the question is the truth of the premises. It doesn't matter what axiomatic system you use if your premises are false. And so what we want to ask ourselves is: which premise is true? Is it possible that God exists, or is it impossible that God exists? And I like to simply leave this question with unbelievers rather than decide it for them. I say, “I think it's possible that God exists. What do you think? Think about it a little bit. Do you really believe that the concept of a maximally great being is like a married bachelor or a square circle? Do you think that it's incoherent? Or is this a coherent concept—that of maximal greatness?” And let them chew on that a little bit. Don't try to prove too much. Just leave them with the argument that if it's possible that God exists, then it follows that God does exist.

Kevin Harris: And by the way, they admit at the end of this paper that even if their argument and conclusions go through, we could still discard the ontological argument and look for evidence for God in other arguments. So in conclusion, Bill, I suppose this is all just an interesting exercise in modal logic, and we can wait and see whether there are any academic responses besides yourself to this paper. Maybe we'll do a future podcast. I can do some more homework on it and get my stuff down. But from what you've heard, do you think the ontological argument is in danger of being undermined?

Dr. Craig: Oh, not at all. I think this is really a very poor response. And in general, I'm not very impressed with the reverse ontological argument. When I ask myself about my own modal intuitions—is maximal greatness possibly instantiated?—I think we have positive modal intuitions in support of the truth of that premise. And we have these a posteriori considerations, like Josh Rasmussen's value argument, in support of the key premise of the ontological argument. We have no such intuitions or arguments in support of the key premise of the reverse ontological argument.

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