In Our Time - The Ontological Argument

Episode Date: September 27, 2012

Melvyn Bragg and his guests discuss the Ontological Argument. In the eleventh century St Anselm of Canterbury proposed that it was possible to prove the existence of God using reason alone. His argument was ridiculed by some of his contemporaries, but was analysed and improved by later thinkers including Descartes, Spinoza and Leibniz. Other philosophers have been less kind, with the Enlightenment thinker David Hume offering one possible refutation. But the debate continued, fuelled by interventions from such heavyweights as Immanuel Kant and Kurt Gödel; and it remains one of the most discussed problems in philosophy.With:John Haldane Professor of Philosophy at the University of St AndrewsPeter Millican Professor of Philosophy at the University of OxfordClare Carlisle Lecturer in Philosophy of Religion at King's College LondonProducer: Thomas Morris.

Thanks for downloading the In Our Time podcast. For more details about In Our Time and for our terms of use, please go to BBC.co.com.uk forward slash radio four. I hope you enjoy the program. Hello, in the late 11th century, a man called Anselm, an Italian prior at a monastery in northern France, who became Archbishop of Canterbury in 1093, started to wrestle with a philosophical problem.

He wanted to prove the existence of God. In a revelation of inspiration at Matinsworn morning, he saw the solution and wrote it down in a work known today as the discourse. It's the ontological argument. Anselm believed he had found a single argument which demonstrate that God exists. It's a simple line of reasoning which has proved enduring, although in the last 900 years many philosophers have had a go to disprove it. Descartes, Hume and Kant all wrote important works about it,

and the young Bertrand Russell experienced a philosophical epiphany on a trip to the tobacconist, declaring great God in boots the ontological argument is sound. We need to discuss the ontological argument are John Haldane, Professor of Philosophy at the University of St Andrews, Peter Milliken, Professor of Philosophy at Hartford College, Oxford, and Claire Carlyle, lecturer in philosophy of religion at King's College London. Peter Milliken, philosophers, as I understand it, recognise three main types of argument for the existence of God. Would you begin by outlining what these three are? Yes, certainly. These are the three sort of most famous kinds. There are others, but they're the ontological argument. the cosmological argument and the design argument. The design argument is probably the most familiar one. That look around the world, see how wonderfully designed it is, all these animals, plants, maybe the laws of nature beautifully attuned to produce this kind of world.

They're all signs of intelligent design. So that's the design argument, also called the teleological argument. Then the cosmological... So there must be a designer in that argument. Exactly. There's intelligent design, there must be a designer. Exactly. Then there's the cosmological argument,

which relies on much sparser premises about the world, like just that there is anything. The fact that there is anything at all rather than nothing requires an explanation or an original cause. We find everything has a cause. If we trace back the chain of causes, then ultimately we must come to a first cause.

And that, for various reasons, is God. So a cosmological argument as opposed to a design argument goes from very general facts about the world. That there's a world at all, that there are causal relations in things at all. Now, the ontological argument starts from even less. It just takes a definition of God. God is the most perfect being. Existence is a perfection. Therefore, God must exist. That's a very crude parody, something like the argument that Descartes used. But you can see that whereas the design argument is appealing to quite rich facts about the way the world is organized, the cosmological argument is appealing to the fact that there is a world at all. And that the causes go back to

the first cause? Yes, that's right. It standardly involves these kinds of arguments that you can't have an infinite regress. There must be a first cause of everything. But the ontological argument is what we call a priori. That is, it aspires to argue from no empirical premises, no premises about the way the world is at all. It just starts from a definition or an understanding of what God is, a most perfect being or something like that. Can you tell us a bit about Anselm, who first formulated what became known later,

actually, by Kant as the ontological argument? That's right, yes. Well, Anselm, as you said, he had been in the Abbey of Beck in Norman. and he became abbot there, and then in 1093 he was appointed as Archbishop of Canterbury. He was actually the second Archbishop following the Norman conquest. But earlier than that, he had published the work commonly known as the Prozlogon, in which he presented this neat argument, and it seems to be original with him. Now, it's a bit more complicated than Descartes' argument.

I mentioned Descartes basically says God is a perfect argument. being the existence is perfection. What Anselm wants to do is focus on the concept of God as something than which nothing greater can be thought. So God is by definition something so great that you can't possibly think of anything greater. Can I turn to John Holden now? Did this come, as we read that it came in a revelation, how did it happen before this notion? Had somebody had the idea before? Well, I think that, I mean, just to pick up on what's been said,

Prior to this proslogion text, he's got another text in which he outlines various arguments of the sort that have been mentioned earlier. And he's struck by the thought that in some sense it ought to be simpler than this. Is there a master argument, a single idea, all these elaborate arguments about design and one thing and other? That's all very well. But is there some single idea that will do it. And what he is very struck by, and this is a very profound thought, I think, is that there is some connection between certain sorts of ideas and there being a reality to which they can. correspond. Now that thought is a very ancient one. I would trace this back to pretty much the

beginnings of philosophy or at Henry very early on, five centuries before the common era, in particular I think are Parmenides. And Parmenides wrote some massively long poem of which we only have some remaining fragments. But in that he says, how is to inquire, how is inquiry to go on? But we can either think about what is not, but that makes no sense, or we can think about what is. So this is what he calls the way of being. And very early on in that, he argues that only what is can be thought, right? That there's some tight connection between the possibility of thinking clearly, as it were, thinking truly, and what is. So I think that the roots of this... Would you include the word exists? Yeah, yeah. Being or exists and so on. So what

he would say is this, only what is can be thought to be, right? That's the sort of central idea here. Now it's a very mysterious thought and it could be elaborated in various ways. It doesn't seem very plausible but Parmenides addresses that. But this thought resonates down through the centuries. It gets picked up by Plato, who sees a tight connection between thinking and being. It gets picked up by somebody called Plotinus

who's a principal influence in the development of Neoplatonism and it's picked up again by Augustin in the Christian tradition and it becomes a thread within Augustinian thinking. That is to say that strand of Christian thought whose origins, philosophical origins, lie with Plotinus and Plato. And the interesting thing is this,

those people who are impressed by the ontological argument, I mean, historically, who take it up and so on, all more or less stand in one way or another in that Augustinian-Platonic tradition. So, for example, Descartes is very impressed by Augustine. Anselm is Augustinian in his formation and so on. So I think there's a deep root here, which is the thought that if you can think of something clearly and distinctly and so on,

that is in some sense a guarantee of its reality, of its truth. And what he does is applies that to this super concept, the concept of a supreme being, and thinks if you can think that, then in a sense there must be one. So what you do is you make a statement, which is a standing start and the basis for logical development into a conviction. because he talks about God being that than which nothing greater can be thought. So that seems to me he's just making an assertion a declaration, isn't he?

Well, no, I think he's picking up on something that has been said through this period. For example... Yeah, but it's still a declaration, isn't it? Sorry. It is, but, I mean, Augustine, for example, 700 years or 600 years before this, has a similar phrase. He says, God is that than which nothing greater can be. or be thought. So this idea that God is the supreme ultimate reality. Now, for any reader or listener in this intellectual world to which Anselm is speaking, they would agree with that. That's it. They'd say, yes, that's right. God is the supreme being. Sorry, can I, because it's the next question I was going

to ask you, John. He's talking about this in the context in which people would accept this as a proposition, whereas many people now would simply not accept it as a proposition to begin with. Well, that's probably what we're going to explore because I think it's a definition. Can we talk about Anselm's medieval world? and why he made so much impact. You've talked about Feminides and Augustine. You brought it forth. But what was in his world

in the 11th century that allowed it to be welcomed so much into philosophical discourse and continue there till this day, till now? Well, remember after the sort of decline of the Western Empire, after the decline of Rome and so on, the cultures, where the high culture

retreats into the monasteries. And those monasteries are Benedictine. And he, of course, is a Benedictan. from Monte Cassino of St. Benedict and so on, all the way through. So the monasteries are the places in which, where learning has been preserved. After about 1,000 Western Europe is being rebuilt. Civil administration through the church and so on is being rebuilt. The monastery schools attached to these Benedictine monasteries

become extremely important because knowledge is going to flow back out into culture and so on. Their high prestige, there seem to be places of great learning and so on. Anselm was really the first great figure of the high Middle Ages because he develops a technique as it were of a reasoning and argument that is highly systematic, very precise, highly dialectical and so on. He's a powerful figure, but it's almost as if there's re-released into the wider culture

those centuries of learning that have simply been sat upon or reflected upon and so on. And I think it's taken up very quickly. And of course, as Peter mentions, he ascends to a position of some ecclesial power in being Archbishop of Canterbury and so on. There's prestige with the office, but I think he's seen as being a very important figure

for the re-establishment, as it were, of public discourse around questions of learning and knowledge and theology. And what you've said is that the monastery is doing the thinking. Exactly. They're doing the thinking. Yeah, this is really before the development of the universities. Yes.

And so his idea would play, well, no, my husband, get on with it. His idea would play very easily, as it were, to the intellectuals who would be reading him or listening to. Yes, though as we'll probably come to, he's immediately criticized by one of his confreras, somebody called

Garnello, who responds to Anselm's argument. So it's not as if he gets an easy run at this. I mean, somebody comes back and says, look, this can't be right. We can talk about that, perhaps, if you'd like to, but... Clerk Arlal... Well, we're going to talk about it now. But I'm going to switch to Claire Carly, if you don't mind. One of Ansel's first and immediate critics,

there's another Benedictine monk, Guanilo, and what did he, we've been led in that direction. What were his objections? Well, one of the clever things about Anselm's argument is that he begins with a concept of God that than which nothing greater can be thought, which he thinks that even a person who denies God's existence has to assent to. So even if you say that God doesn't exist, in order to say that, you have to have a concept of God in order to deny that he exists. And so Anselm begins by talking about the fool

who in his heart says there is no God. That's in the Psalms, isn't it? That's right, yes. And so Garnello wrote a reply to Anselm entitled On Behalf of the Fool. So it's a kind of defence of the fool who denies the existence of God. And I guess Garnello is playing devil's advocates here

because I'm sure he would have agreed with with Anselm's conclusion, but he wanted to question the logic of Anselm's argument. So one move that Anselm has made is to say that God is that than which nothing greater can be conceived. Things can either exist in the mind only. For example, something like a unicorn is something that only exists in the mind. Or things can exist both in the mind and in reality. so I can have an idea of John. It's in my mind, but John's also here today.

And Anselm's basic point is that it's greater to exist both in the mind and also in reality than to exist just in the mind. And so if God is that than which nothing greater can be conceived, he can't exist only in the mind because there's something greater than that, which is existing in the mind and in reality. So that's really his basic argument. and Garnillo takes issue with this reasoning. So first of all, he attacks the premise of Anselm's argument,

which is that this concept of God exists in the understanding. And Garnela says, well, just because I hear the words, that than which nothing greater can be thought, that doesn't mean that I actually have that concept. There's a difference between just sort of hearing those words and really having the idea in my mind. So that's one criticism he here. has. He also says that in fact God's reality cannot be conceived at all, that God's reality is

something that's beyond human thought, beyond human understanding. And he also says that it's possible that the idea of God could be in his understanding, but it's just a false idea, like any kind of idea, like the idea of a unicorn or something like that, that we have all sorts of ideas in our mind, but they might be false. And the idea of God might be something like that. But actually, I think Garnello's most significant objection and most ingenious objection is a counter-example that he offers to Anselm's argument. And he says, well, what about the idea of a perfect island, the most excellent island? You know, I've got this idea of an island, it's better than any other island that I can conceive. If this existed only in my mind, there'd be a greater island which also existed in reality.

So according to your reasoning, Anselm, you know, I could prove the existence of this perfect island. I could prove the existence of all sorts of perfect things, most excellent things. And that really is quite a sort of striking criticism to the logic of Ansel's argument. But Anselm then wrote a response to Garnillo. and in responding to Garnelot's counter-example of the Perfect Island, I think he really brings to light what is most important in the ontological argument. And that is to say that what Anselm's argument really expresses is the uniqueness of God and the fact that God is something completely different from anything else.

Because Anselm doesn't even bother to, he just sort of rejects this counter-exam. example is something quite absurd because he says, well, no, God is the only being that the ontological argument can apply to. Only God is that than which nothing greater can be conceived, and that's the only concept that really we can define into existence in that sort of way. And Anselm insists that when the thing is printed again, not printing again, published again, that his argument and the other are both included. Thomas Aquinas brought his guns against it. Can you briefly tell us how, briefly what he said

and how that sort of stopped the argument for a few centuries? Yes, well Aquinas has two objections to Anselm's argument or rather to the ontological argument. I'm not sure whether he was actually engaging with Anselm directly. First of all, he questions Anselm's assumption that his definition of God is something that's universally accepted. Aquinas says, no, we don't all agree. on a concept of God.

We don't all share this concept. So that's his first point. But then he says perhaps more significantly, okay, let's say that we do accept this concept of God. It doesn't tell us that God exists in reality. All it tells us is that when we think of God, we have to think of him as existing. So the argument tells us something about what we must think

and how we must think of God. But this slide from the realm of thought to the realm of actual existence is illegitimate and it doesn't tell us about God's actual existence. Peter Milliken, as I say, Aquinas sort of seems to have suppressed the argument for a while because of his power as a thinker. Descartes came up with his own version

which you actually alluded to at the very beginning of the programme. What was that version? And why did he have that version instead of Ansel's version? Because you make it quite clear. You think his version is cruder and weaker than that of Ansel. Well, I think it's crude. and less subtle. I think Anselms has sufficient logical complexity

that you can tease out a lot, a lot more clever ways of trying to defend it. Whereas Descartes wanted an argument which one could simply see by an immediate, clear and distinct perception. Within his philosophical system, famously he starts from skepticism. And to refute skepticism, he comes out with this famous,

I think, therefore I am. as something certain. But to get beyond... That he stands on that. That's where he stands. That's right. And because he clearly and distinctly perceives his own existence, he then concludes that anything that he comparably

clearly and distinctly perceives must be true. And to get beyond his own thought to the external world, he wants to vindicate belief in God, because if he's been created by a perfect God, then his faculties can ultimately be relied on and so on. So the ontological argument fits into day, Descartes system as a very simple argument that can be perceived as it were by a clear and distinct perception. God is that which is most perfect, by definition, the perfect being.

Descartes sees clearly and distinctly that existence is a perfection and therefore God must exist. Can I go to John Holden now? Descartes has been called the first modern philosopher. How did he, as it were, turn the argument so the modern world continued to pursue it? Well, can I just, I mean, I pick up from where Peter's speaking. Look, I think one thing is this, that in Anselm's argument, among the premises, is a claim about something existing, namely the idea of that than which nothing greater can be conceived existing in the mind, all right?

So that's where we start from, and then the ideas, but there's some greater existence, which is outside of the mind and so on. Descartes' argument doesn't start from a claim about anything existing. It simply starts from a definition, right, of the idea of God. but what it seems to me is problematic about Descartes is that he slips existence into the definition of God. Now it's not clear that Anselm actually does that, but we can perhaps debate this, but he certainly does. And a way of seeing both the power and the fallacy, if I can put it this way, and Descartes is this.

It would be like saying something like this. Look, think about the concept of a cat, right? The concept of a cat is the concept of a living thing. Fair enough. Well, something that's living is something that's alive, but you can't be alive unless you exist. So the concept of a cat guarantees the existence of cats. Now, you'd say, well, hang on a second, that can't be right, of course, the concept of a cat includes the idea that a cat is a kind of living thing,

but it's an open question whether or not there are, in fact, any cats. So he's slid, as it were, from living thing as being part of the definition of the idea of a cat to, therefore, there are these living things cats, and that's just obviously a fallacy. Now, the thing with Descartes, but Descartes, of course, he's a brilliant philosopher, So it doesn't emerge quite as crudely as that. But what he does, remember, he belongs to an age that is obsessed with the thought that by reason alone we can determine some fundamental facts about reality. This is going to be, of course, swept away and rejected by the British empiricist philosophers

who are going to say that the only reliable route to knowledge about reality is experience. But here we're dealing with the rationalists, the continental rationalists, and we'll hear later about perhaps Leibniz and Spinoza and so on. But what Descartes does is Descartes, I mean, it's bold and brilliant. Descartes thinks we can, look, if I just close my eyes and bring to bear the power of thought, I can disclose to you something far more profound than just what happens as it were to be in the room, the underlying structure of reality. And that is such a powerful and potent and exciting thought.

And he does it with such flair and brilliance, that there's a long period in which everybody is stunned by Descartes and they think he's proven the existence of the self, he's proven the existence of God and so on. One point to make here is that Descartes does face up to the so-called parody objection, which John has alluded to, the idea that you can just say, well, take the idea of a unicorn, an existing unicorn. Well, that contains the idea of existence, therefore there must be a unicorn.

And we don't think of that as a good argument. And Descartes wants to compare the idea of God with the idea of a triangle. So take the idea of an equilateral triangle. You can actually prove things about it. That shows that this idea has some reality to it. It's not just a dreamed-up concept. And he wants to say in the same way that the idea of God has a sort of natural unity to it. It isn't just an arbitrary idea that has existence pushed in there.

Claire, John Holden referred to Spinoza. Could you tell us how he, because this argument, is picked up by Descartes, although not directly connected with the ensemble, but it is the argument. And it keeps going on very steadily up to the present day from then on. So can you tell us what Spinoza brought to bear? Yes, that's right. I mean, I think it's probably debatable whether Spinoza has an ontological argument,

and that's because he tends to twist or invert traditional, both religious and philosophical ideas. So in his ethics, at the end of, towards the end of the 17th century, in his ethics, he has a kind of reversed version of the ontological argument. So Spinoza begins the ethics with a concept of substance. And substance is something, it really signifies existence. It's just a concept of existing and crucially existing independently, so not being dependent on anything else.

So substance is really the most basic concept of existence. And then Spinoza goes on to say that many of the traditional divine predicates, apply to this concept of substance or existence. So substance is eternal, infinite, all-powerful, all-knowing, because it contains all thought and all understanding within itself, it's self-causing and the cause of all other things. So instead of starting with the concept of God and saying that it must exist, Spinoza rather starts with a concept of existence,

a certain concept of existence, and says that, well, this must be God. So we still have in Spinoza the linking together of a concept of existence and necessary existence and then the divine attributes. So as I say, it's a kind of reversal, quite an ingenious reversal of the ontological argument. You mentioned John Holden, you mentioned the German thinker Leibniz, who reinforced the argument or took the argument of Descartes on. Can you take it on for it? Yes. Leibniz says, look, this is a very interesting argument. This is the Descartes argument.

By the way, Descartes doesn't acknowledge Anselm's. being the source of his argument. Leibniz, however, does characterize Descartes's argument as having its origins in Anselm. So whether or not Descartes was being disingenuous, who knows. But at any rate, Leibniz says, look, this argument is pretty good, but it omits something, there's something it hasn't considered, and that is the possibility that, in fact, the idea of God is incoherent or has some contradiction contained within it. Okay. So what Descartes really needed to do, first of all, was to show that the idea of God contains no contradiction, and it includes this idea of perfect existence and so on,

and then we're off. But you first of all have to show there is no contradiction in the idea of God. See, otherwise it might be, I might run an argument about, say, you know, square circles or something of that sort, and somebody might say, well, look, this argument can't possibly work because there couldn't be square circles. There couldn't be something that was both four-sided and round, basically. So what Leibnett says is we have to make sure, first of all,

that there is no possible source of contradiction in the idea of God. And once we've eliminated that, we see that the idea of God, a non-contradictory concept of God includes existence and then we're off. And that's the argument. So what he says is this, and he says, look, to show that there's no contradiction in God, we just have to show that the various predicates or attributes or characteristics that are ascribed to God, none of them is incompatible with any other one. And since they're primitive, they're brute, they're simple, they couldn't be. They're not things that have a sort of an elaborate structure where we could use. show there was some kind of internal contradiction. Could you rerun that?

All right, okay. So, for example, supposing somebody is wondering whether or not a certain kind of thing could exist or not, one way of showing them that it isn't worth investing money on a search to go and discover one would be by showing there just couldn't be anything of that sort. So, I mean, if scientists wanted to get vast sums of money to go and explore some far reaches of the world

to discover whether or not there are squads. circles, as somebody at the Research Council would say, look, we don't need to invest money in this, because straight off by definition we can see there's a contradiction in that. So no amount of investigation is going to discover a square circle. So what Leibniz is saying is, before we can work out whether or not there could be a thing of this sort, we need to make sure that there's no contradiction involved in the idea of God. Now, later philosophers famously wanted to argue against the existence of God precisely on the grounds that there is some internal contradiction in the very idea of God.

So to illustrate, supposing somebody says, God is an agent, God acts, indeed God acts everywhere in the universe, but God is also an immaterial being. Some people have thought there's a contradiction in that. In order to be able to act, you have to be, let us say, physically present. If you're immaterial, you have no physical body, you can't be physically present. So they're going to argue there's a contradiction in the idea of an immaterial agent. There's a contradiction.

So what Leibniz says is, let's look at the attributes that is traditionally assigned to God, that he's all powerful, that he's all good, that he's all knowing, so on and such like. If we look at each of those, none of them implies any contradiction with any other one. So the idea of God is a coherent idea. And, moreover, it includes the idea of existence. Descartes reminded us of that, and so we're off. So all that Leibniz is doing is really clearing away a possible objection from the idea of God to the existence of God

an objection that would say the very idea of God is an incoherent or contradictory one. No, it isn't, so off the argument goes. Peter Milliken, as I understand in 18th century, David Hume comes in extremely powerfully against the whole thing. A point of view that perhaps our listeners will be relieved to hear arrives on the scene.

It doesn't destroy the argument, it goes on for another 200 years or so. It's still going on. But he makes a powerful case against the ontological argument. And he starts underneath, blazes down, and he plunges it in and blows it up as far as he is concerned. Now, can you tell me what it does? Yes, I think Hume's way of looking at the ontological argument

has been very influential, particularly in the 20th century. I mean, it was taken further by Kant and Fregear in various ways, but essentially Hume's thought is this. If you think of an object and then think of the object existing, those are just the same thing. To think of a unicorn is to think of a unicorn as existing. So existing doesn't add anything to the concept. The concept of a unicorn already includes.

So the idea that the concept of God leads to the existence of God, he is saying no. He's saying take any object at all, God or anything, thinking of it is thinking of it as an existing thing. It's not adding an extra property to it. So it exists in the mind and that's where we are. Yeah, but that kind of talking, of course, is apt to lead to problems because you...

Well, that's what you're about you. Which is why the ontological argument is so interesting. Let's not talk about existing in the mind at the moment, because we're thinking of David Humes, who's a very kind of down-to-earth, straightforward philosopher, you've got the idea of God in the mind. Let's not talk about God existing in the mind. The idea of God is the idea of God existing,

just like the idea of a unicorn is the idea of a unicorn existing. And Hume says, whatever you can think of existing, you can also think of it not existing. So one way of putting that would be this. You take the concept of the object, the thought that you have of it, and then the question of whether there really is one is a quite distinct question. But to think of a unicorn is just to think of it existing, and God is no different in that sense.

So Hume wants to say quite generally that any kind of thing we can think of, we can think of it as either existing or not existing, unless of course it's a contradictory concept like a round square. Can you, Kant, as I understand the German, think it was very influential and was influenced by Hume, wasn't he, in this? And we're coming into the nature, coming to the iron world existence now. So can you, and the property or the weight that existence has, can you take us there? Yes, that's right.

I mean, as you say, in a way, Kant gives a slightly different expression to Hume's basic thought that Peter's just outlined. But Kant expresses it in a very clear way, which many people have taken to be a pretty definitive rejection of the argument, or defeats the argument. And he says that existence

is not a predicate. Now, what he's doing there is, well, first of all, he's actually responding to Descartes version of the argument. So Descartes, remember, says that God is the most perfect being, therefore he possesses every perfection, including things like

being eternal and knowing everything and being all powerful and also he also of course has the perfection of existing and so what Descartes is doing there is really treating existence as one kind of property that things can have so you know existence is just treated like something like being big or being blue or being furry or whatever and Kant says no existence is not like that existence is not a property or a predile

at all. So predicates tell us what something is like. So if you put a group of predicates together, then you get a concept of something. You mean tall? Yes, exactly. Exactly. Yeah. So, you know, the concept of Claire is being female and having blonde hair and having blonde hair and being a certain height and weight and so on. And that's the concept. But existence isn't, doesn't tell us more about Claire. This is, this is, this is, this is, this is, this is, uh, Kant's, claim that to say that something exists is not to tell us about what that thing is, it's just to make a judgment that there are such things in reality. John Holden, we've got Hugh and we've got Kant, where does that leave the ontological argument before we move closer to our own time? Well, it focuses on this question of existence. This is what's really come on to the scene now.

If I could just sort of gloss what Claire said, I mean, a very simple way of what was putting this is it's not part of the definition of anything that it exists. I mean, if you just had a very simple encyclopedia, let us say, that just define the natures of things and so on. It could define the nature of all of these things, but it's never part of the definition of the nature of a thing that it actually exists. So you might say, oh, tell me about these things, you know, such and such. And then it's a further question, are there any? whereas and the objection is that what Descartes and what others have done with the ontological argument is made existence part of the definition of a thing.

But existence is never part of the definition of a thing. So they've treated it as if it was part of the definition of a thing. But for anything that you define, you can always ask the question, well, thank you. You've told me what they are, but now tell me, are there any? So that's the burden of where the thing goes now is over this question of whether or not it makes sense perhaps uniquely in the case of the definition of God to say that existence is part of the definition.

Of course it's not part of the definition of cats or dogs or mice or rats that they exist. Of course they do exist, we wouldn't be interested in defining them if they didn't. But you could come up with the definition of something and then it would be an open question. Scientists do this all the time. You know, here would be a definition of a kind of particle, right? Are there any, right?

So then they go off and do the experiment. So they defined what the characteristics of the Bosan might be and then they go off and they do that, CER, and they do their work, and they find out whether or not there are any. But the argument is this, or the argument becomes this, might it be the case that, with regard uniquely to this one kind of thing, namely God, that existence really is part of the definition or part of the understanding of God?

And one way in which that is put is to say, look, sure, existence, ordinarily speaking, isn't part of the definition of anything, but necessary existence. it being impossible that such a thing not exist might be part of the essence or definition of God and I guess you might say that in one way or another the revival of the ontological argument in modern times I mean in the last sort of 50 or 100 years and so on

has really been around this dialectic this argument to or fro as to what it is legitimate to put into the definition Peter Milliken the man described as the greatest mathematician of the 20th century Kurt Gödel was on the side of the ontological argument. Can you say, can you tell us what he's, how he reinforced it, added to it? Yes.

Well, in the early 70s he circulated amongst Friends, a manuscript which was never actually published. But essentially, Gerdl's thought moves on from Leibniz's. He has the notion of a positive property. a property, we can think of this as a property that is necessary for and compatible with perfection. So if you say these are properties that are perfect being would have to have. And he gives a formal proof that thus conceived these positive properties ought to be compatible with each other. He asserts, as John has said, that necessary existence is a positive property, and he draws the conclusion that a being characterised by these properties,

must necessarily exist. So essentially what you've got there is a general, very abstract conception of a positive property. And then he's arguing that a being thus characterized must exist. Can we go to this man called Alvin Plantinga, John Holden, in the 60s? Again, we're still 800 years on, whatever it is, re-examining this ontological argument. Although in general, it is dying way. fewer and fewer people are believing it. I think it's very interesting.

Some think it's a joke. They think it's a necessary part of the way that they learn logic in philosophy, but it's losing its sting. Well, maybe. We'll come back. There's a final question. With regard to Plantinga. So Planting is an American philosopher who's very interested in what's called modality,

and that is this business of what is possible, what is necessary, and so on. So if you remember, Peter said about Hume, what Hume thinks is that anything that can be might not. be. So what exists is an entirely contingent matter, as it were, right? There's nothing that must be, there's nothing that's impossible to, let's just say, nothing that's in reality

impossible to be and so on. Whereas Plantinga says, look, and along with a number of other modern philosophers and logicians, he says, look, this isn't the totality of things, as well as what is, there is what cannot fail to be and what cannot possibly be. Now that's called modal logic or

model metaphysics, thinking about ways and what being possibly necessary. and so on. And he says this, let's just define the idea of God as being that which is maximally excellent. It has all of these attributes of being all good or powerful, all knowing, etc. and so on. That's maximal excellence. Now let's say that something is maximally great if it exists necessarily, as it well, right? Now the way in which he does that is through the talk of possible worlds, impossible worlds and so on. That gets a little bit detailed. But, Basically what he's saying is this.

Again, it's kind of Cartesian, that the idea of God takes us to the idea that God must necessarily exist. And he uses these techniques of modal logic, of playing around with notions of possibility and necessity and so on. And basically the line is this, God couldn't be the kind of thing that might or might not exist. God is the sort of thing that must exist if it exists at all.

Peter, and then I want to come to Clarke. Yes. I mean, one problem with that kind of argument is that it is vulnerable to the same kinds of parodies. I mean, suppose, for example, I define an N-unicorn as a unicorn that necessarily exists. Then by exactly the same kind of argument, you can say that such a being is either necessary or impossible.

Now, in fact, most of us would say, that's impossible. A unicorn isn't the sort of thing that can necessarily exist. So an atheist, faced with Plantinga's argument, is actually going to draw the conclusion that God necessarily doesn't exist. as Plantinga has defined him. Can I come to you for the beginning of the sort of summary here, Claire Carlisle. Is it any more than an intellectual, interesting, intriguing intellectual puzzle at the moment,

or does it have any real power, do you think, as an argument for a belief in God? Well, I personally don't think that there is a successful argument for the existence of God. However, I don't think that the ontological argument is just, a sort of intellectual game or puzzle either because I think it expresses something quite profound I think it has a religious significance and that's to say that particularly Anselm's version actually I mean I would I would always want to go back to Anselm

as still the most interesting proponder of the argument and what Anselm does in his text is take a very important aspect of belief in God, which is a religious idea that God is great, that God is either beyond what we can conceive or right at the edge of human understanding, and also that God is a unique kind of being. He cannot be conceived not to exist,

and so he has more being than anything else. And what that thought gives you is a sense of the difference between God and all other things. So it's a difference between creator and created things. It's a difference between God and everything that depends on him. And that ontological difference in the sense between the being of God and the kind of existence that belongs to all other things is a profound and important theological idea.

And Anselm very cleverly gives a logical and philosophical expression of this, even mystical and certainly religious concept. John Holden, what would your position be on the question I asked? I think there is something very deep here going on. I think that the objections to the argument in terms of existence and building in existence and so on, I think those are well-founded. But that raises the question as to whether or not Anselm has something else in mind, which I suspect you may have.

But basically, the key thought to dwell on is the idea of something that is the greatness of God, right? and wonder whether God's being doesn't flow from that. And finally, I'm afraid briefly, Peter. What resonance does it have for you? Well, I think it's a fascinating argument. It raises all sorts of interesting questions. We've talked about existence. But those discussions still go on.

We do want to say there's a difference between something being fictional or legendary or being real. I think it's a very interesting puzzle. Thanks very much, Claire Carlis, Peter Milliken and John Haldane. Next week, it's the medieval chronicer Gerald of Wales. Thank you very much for listening. If you've enjoyed this BBC podcast, why not try others such as The Forum, the discussion program about global ideas? To find out more, visit BBCworldservice.com slash forum.