Existence of God (part 23)

March 13, 2011     Time: 00:38:51


The Ontological Argument.

Excursus: Natural Theology
§ V. Ontological Argument
Lecture 1


The Ontological Argument for the existence of God was originated by a Benedictine monk in the 11th century named St. Anselm, who was the Archbishop of Canterbury. Anselm had been working on arguments for the existence of God – he was a natural theologian. But he was frustrated because he wanted to find a single argument that would prove that God exists with all of God’s superlative attributes. And he had nearly given up on this quest when he came upon the concept of God as the greatest conceivable being. God, he said, must be the greatest conceivable being because if you could conceive of anything greater than God, then that would be God. By definition, the concept of God is the concept of the greatest conceivable being.

Anselm believed that once a person came to truly understand this notion of a greatest conceivable being, then that person would see that such a being must exist – the existence of God follows from the very concept of God. That is why Anselm believed the Scriptures say that “The fool has said in his heart there is no God” – because once you understand the concept of God, you will see that God must exist and, therefore, anyone who asserts that God does not exist is uttering a logically incoherent statement.

Anselm’s argument came to be known as the Ontological Argument from the Greek word “ontos” which means “being.” The thing that makes an ontological argument an ontological argument is that the argument attempts to deduce the being, or the existence, of God from the very concept of God. Once you understand the concept of God, then you will see that God exists.

The argument has gone through a long history of revision and development, and the version that I want to share with you in this class is one that has been developed by a man who is widely regarded as the greatest living Christian philosopher: Alvin Plantinga. In order to understand Plantinga’s argument, it is helpful to have a little bit of philosophical background so as to grasp the argument.

Philosophical Background

Possible Worlds

Plantinga’s version of the argument appeals to the language of “possible worlds.” What do we mean when we talk about possible worlds? We are not talking about planets or even another universe. Rather, by a “possible world” one simply means a sort of maximal description of reality. I think maybe the best way to think of a possible world is to think of it as a conjunction of true propositions. Let’s imagine some propositions p, q, r, s, and so on. These would be statements like, “Joe Jones teaches at Georgia Tech,” “Georgia Tech campus is in Atlanta,” “Bob Smith attends Defenders class at Johnson Ferry Baptist Church.” These are all just various truths or various propositions. You can imagine a possible world as just a huge conjunction of such propositions:

p & q & r & s & . . .

so that all of the propositions that are true are included in that conjunction. We can alter some of these propositions – we can negate them – to arrive at a different world. For example, a series of possible worlds might be:

World #1 could be: p & q & r & s & . . .

World #2 could be: not-p & q & not-r & s & . . .

World #3 could be: not-p & not-q & r & s & . . .

World #4 could be: p & not-q & not-r & not-s & . . .1

Each one of these will represent a different possible world – a maximal description of the way reality might be. When we are talking about possible worlds, we are not talking about parallel universes or other sorts of worlds that exist, populated with actual people and things. We are just talking about abstract descriptions, maximal descriptions, of the way reality might be.

Since each one of these worlds has to be a possible world, that means that the propositions that make up the conjunction need to be able to be true together. They need to be able to be true individually, and they need to be able to be true conjunctively – that is, together. For example, take a proposition like “The prime minister is a prime number.” That is not even possibly true. A prime minister could not be a prime number because a prime number is a sort of mathematical abstract object, which couldn’t fill the role of a prime minister. So that proposition will not be even possibly true. It is not a member of any description of reality. That proposition will be false in every possible world. It will be necessarily false that the prime minster is a prime number. So that proposition will be false in every possible world.

But by contrast, take a proposition like “Hillary Clinton is the President of the United States of America.” That proposition is not true, but it is possibly true. There is a possible description of reality in which Hillary Clinton is the President of the United States. So that proposition is true in some possible worlds. There are descriptions of reality in which that proposition is true. To say that Hillary Clinton is the President of the United States in some possible world just means that there is a description of the way the world might be which includes that proposition in it.

To say that God exists in some possible world is simply to say that the proposition that God exists is true in one of these possible worlds. To say that God exists in a possible world is simply to say that that proposition is true in one of these descriptions of reality.


Question: Some would say that God does not exist in this real world that we live in. I am having difficulty how to calculate that into what you said.

Answer: If a person says that God doesn’t exist in the actual world, that is to say that this proposition is false in the description that is the actual world. In other words, one of these worlds that we have mentioned here is the actual world. The actual world is a possible world. Let’s call the actual world, say, Alpha, and maybe it is World #3. So World #3 is the actual world, and these other worlds are not actual. And in this actual world the atheist is claiming the proposition “God exists” is false. As theists, we disagree – we think that that proposition is true in the actual world, that God exists, but the atheist disagrees. He’ll say that proposition is false in the actual world.

Question: I thought about this argument for some time and to me it is about 99% question begging. [Dr. Craig interjects and says that he hasn’t presented the argument yet and don’t poison the well before we drink!] I don’t buy the argument and the first reason I don’t buy it is this #2. [Dr. Craig interjects again and says we haven’t got to #2 yet – we are still just defining our terms!]. OK, then forget the numbers and let’s continue with what you just said. The idea of possible worlds is a bogus concept or one I don’t get. You said there is a world in which Hillary Clinton is President of the United States. Yes, there is and I would call that Wonderland.2 That is a fantasy world; that is not a real world [Dr. Craig interjects and says, “Right, I agree!”]. So, if something possibly exists – first of all, you said it is not given; it is only a possibility that it exists – so if it is a possible proposition such that something exists in some possible world. Well, yeah, but that world is perhaps a fantasy world, so what good is it? We can all imagine a world where anything can happen – we can have giant bunnies and a one hundred foot Sta-Puff marshmallow man or anything we want. But as long as it is possible, how does that relate to truth? And you said this is a description of reality? That is no description of reality. There is no reality in which Hillary Clinton is President of the United States.

Answer: I largely agree with what you say. These other worlds, you can call it “Alice In Wonderland World,” or “Fantasy World,” or anything like that, that is fine. All that these are are maximal descriptions of the way reality might be, not the way reality is. We have already said the actual world is described by one set of propositions. But those propositions are not necessarily true – they could have been false. And if they were, you would have another description of the way the world is. That doesn’t mean that just anything could be. As I said, it is impossible that the prime minister be a prime number – there is no possible world in which that is true. There is no possible world in which there are married bachelors or where there are round triangles and things of that sort. So this idea of possibility and necessity is definitely an important idea, especially when we are trying to sort out nonsense from what is meaningful. Very often people will assert self-contradictions, and they need to be told that that isn’t even possible. There is no possible world, for example, in which God is evil and creates people that go through unremitting suffering and never have a chance to experience good. That is an impossibility – there is no possible world like that.

Followup: One other thing. The phrase “reality might be” – but reality is. And there is no conditions to reality – when you say reality might be, you are having a conditional voice. But reality is, and it is one thin little set, and then everything else is not reality.

Answer: Yes, that is right, but there is this idea here that I think we need to get a handle on of what is called modality. Modality is what is concerned with possibility and necessity.3 You are right: whatever is, is real. Or, whatever is real, is. That is the way things are de facto. But not everything that is, is necessarily. Things could be different, and not everything you can just imagine in your mind is really possible. There are some ways reality could not have been. Self-contradictions, for example. So we are asking questions here not just about the way things are but about the way things could have been, or the way things might be. That is really significant. This idea of the modes of existence is very important. Whether something is possible, whether something is impossible, whether it is necessary, whether it is contingent – these are important questions to ask and intelligible.

Question: Maybe a simple layman’s view of saying this is, “This is the reality of today, but things could change, and then tomorrow we could have a different reality.”

Answer: This raises an interesting question. This is really a knotty problem; and that is, how do you introduce time into these worlds? – because things change over time. So p maybe true today, like “Obama is the President of the United States.” But that hasn’t always been true, and it won’t always be true, so reality itself is changing. So what you would have to do would be to outfit these propositions with times and dates, so that their truth value doesn’t change. You would say, “Barack Obama is President of the United States in 2010.” That is always true if it is ever true. In 40 B.C, it is true that Barack Obama is President of the United States in 2010. And it would be true long after he is dead and gone.

So we are talking here, not just about the way the world changes over time – you are quite right that the world does change over time – , but we are talking here about the way things might have been but never will be.4 For example, God might never have created the world. As Christians, that is what we believe. We believe that creation was a free act of God – that is, there was no compulsion. There is a possible world in which all of the propositions about the things that we see around us, they are all false. What is true in that world is “God exists alone” – there is no universe, there is no time, there are no people, there is no space. You would just have propositions about God and what he does and is and so forth. That is a possible way reality might have been. You see what I mean? We are talking here, not just about change over time, but about totally different ways reality might have been. That is often the way philosophers define possible worlds. They will often say a possible world is just “a way things might have been.” I like the concept of conjunctive propositions because it helps you to make it more concrete – to think of a possible world as just a conjunction of all these propositions that describe the way the world is.

Question: Is this somewhat related to God and middle knowledge?

Answer: It is related in that, if you remember our discussion on God’s omniscience, we said that God is all-knowing and so he knows all possible worlds before he creates this world. He knew the range of possibilities that were open to him to create, and he chose which possible world would be the actual world.

Followup: That affects us because he knows, based on our free will, what we could have chosen and he also knew what we did choose, right?

Answer: I would affirm that, yes. Now here we are getting a little off on a tangent, but you are recalling what we talked about when we talked about the attributes of God. God knows what we could have done had some other world been actual. He knows that I could have been a firefighter, say, or a farmer, or something of that sort, had one of these other worlds been actual. What middle knowledge says is even more radical than that. What it says is God also knows what I would have done, had I been in some other circumstances. Not merely what I could have done, but what I actually would have done. That is even more radical – to suggest that God knows something like that. But that isn’t presupposed in what we are talking about here. So you can just leave that to the side. What we were just talking about here is that when people talk about possible worlds they don’t mean that there are these other mysterious realities out there. These are just imaginary. They are ways the world might have been.

Maximal Excellence and Maximal Greatness

Plantinga’s argument appeals to the idea of God as a maximally great being. What does Plantinga mean by that? First, he talks about what it is to be a maximally excellent being. Plantinga says a being that is maximally excellent would have such attributes as being omniscient, or all-knowing, he would be omnipotent, and he would be perfectly good. If a being is maximally excellent, he’ll be omnipotent, omniscient, and omnibenevolent. A maximally great being will be a being which is maximally excellent in all possible worlds. It would be a being which has omnipotence, omniscience, omnibenevolence in every possible world. That is what it means to be maximally great. That would be the greatest conceivable being, this idea of a maximally great being.


Question: Why does he necessarily have to be omnibenevolent?

Answer: To be loving, to be good, is a great-making property. You are greater if you are loving and have this virtue, than if you are hateful or even cold or somewhat indifferent. These are what are called great-making properties. A being which has them is greater than one which doesn’t, and therefore a maximally great being would need to have these properties.5

Lest you think that this material is so difficult to understand that it is of no value whatsoever, I want to share with you a letter that I just got two weeks ago from a man in Australia who teaches a Sunday school class of children. This is what he wrote:

Dear Dr. Craig,

Greetings from South Side International Church in Brisbane, Australia. I would like to express my appreciation for your excellent ministry, which has been very useful to our church. I am a Sunday school teacher with a class of wonderful students ages 8 to 10 years old. For a while now I have been teaching, and I have used material from your website to prepare Sunday school lessons in apologetics. Your ministry is helping us to teach them a defense of Christianity. For example, one of the students liked the lesson so much that she went home and shared it with her non-Christian father. He previously had thought Christianity was silly, but after reading her worksheet, he said that actually makes sense. I have found the students to be so intelligent that they were taught the Cosmological, Moral, Teleological, and even Ontological Arguments. Not only did they find the lessons enjoyable, most of them even seemed to understand it. I have attached a copy of their Sunday School worksheet so you can see for yourself. (...and then he includes these worksheets...) God is using your work to help these children to become strong in the faith. With God’s grace they will grow up to become mature, intelligent, and active Christians through your work. Perhaps some of them will even decide to become an apologist like yourself when they are older. All of us at South Side International Church again say thank you for the work that you do.

And then the teacher and children sign it.

Here is the Sunday school worksheet that these children work on the Ontological Argument [he shows the class the worksheets].6 And it starts off talking about how to understand the word “possible.” He differentiates possibility of knowledge and possibility of existence. What possibility of existence means is what could exist or what could be real. For example, I could have been fat. Me being very fat is possible. I could have had five sisters. Me having five sisters is possible. I could have been a prince or princess. Me being a prince is possible. You can see from the doodles that the children have filled in all of these worksheets on the Ontological Argument with incredible depth of understanding about these notions of maximal excellence, maximal greatness, possibility, and so forth.

So I get really impatient with adults who depreciate themselves and say, “I am too stupid to understand this.” Nonsense! You are not too stupid to understand this. This is stuff that an 8 or 10 year old can get, and you can get it, too. That is a real encouragement to all of us to see that this material really is graspable.


Question: I am trying to understand that if there are certain attributes that God does have, is he under certain obligations due to having those attributes?

Answer: I don’t think that follows from this. These are further questions that one could ask. For example, you might say, is a being who is omnibenevolent morally obligated to do certain things or not? That will raise really difficult questions. When I talked about the Moral Argument for God’s existence, when we talked about the goodness of God, when we looked at the attributes of God – I don’t think God has any moral obligations. I think moral obligations stem from God’s commands.7 Our moral duties are constituted from his commands, and he doesn’t issue commands to himself. So he doesn’t have any moral obligations. But does that mean God can do just anything and create a world in which, say, children are tortured unremittingly with no hope of escape? No, because that would be incompatible with his character, which is his omnibenevolence. It is not that he has a moral obligation to do something, but it is just that he is too good for some of those things to be possible. I would say that is an impossible situation – there is no possible world in which children are unremittingly tortured with no means of escape.

Followup: Specifically, in certain passages in the Bible, God does obligate himself. For example, in Genesis where he swears by himself when he promises Abraham what he is going to do. When he does that, he seems to obligate himself to do certain things.

Answer: That would be a matter of God’s making a promise. What one would say is that God is faithful and therefore keeps his promises. But he is not under any sort of obligation to make that promise. But again we are starting to go off on a tangent that is interesting and important, but it is not really relevant to the argument that we are considering right now. What we want to make sure we understand now is: do we understand the idea of different possible worlds, different ways reality might have been, and do we understand what it means to be maximally great, which is to be maximally excellent in every possible world?

Question: Isn’t omnibenevolence based on what our idea is of what is good? A societal type of thing? Because in some societies, they would go with the omnipotent and omniscient, but being good would not be part of it. He may be a strong, mighty warrior – that would be more valuable.

Answer: I think that that is open to discussion. That we would have to talk about. Do you think being loving is a great-making property? And it is not clear that all of the attributes that are normally ascribed to God are great-making properties. For example, take the question of God’s eternity. Is it greater to be timeless than to be everlasting throughout time? I do not think we have any clear sense of that. Some people think it is greater to be outside of time, that the greatest conceivable being must be timeless because he would transcend time. But others would say, no, it is greater to be active and dynamic and interacting with things, and therefore it is greater to be temporal but to be everlasting throughout time. There I think we just don’t have any clear sense of which is the greater way. Maybe they are neutral. Maybe they are fifty-fifty or something of that sort. But with regard to other properties, I think we can say that it is clearly better. For example, morally, it is better to be morally loving and kind and generous. Or at least if you don’t like omnibenevolence, replace it with moral perfection. God must be a morally perfect being as well as omnipotent and omniscient.

Question: I think omnibenevolent is an assumption, but it rests on objective moral values which you already addressed. The other thing is: knowing and their being possible are two different things. To me I think you can go from this argument that the maximally great God exists to imply that he is a God of the maximally great reality, which is not perceived now, and everybody struggles with evil.

Answer: Hang on to those thoughts. I thought you were going to go somewhere else with them. But you are quite right there is a difference between knowing something is possible and its really being possible. We will pick that up again later.

Question: I can see where this characteristic of benevolence can be the tripping point because some people can say, “How in the world can this God be maximally benevolent when he told the Israelites to just wipe out certain nations?”8 In more recent history, how can you say he was benevolent when he allowed the Holocaust to take place and didn’t intervene to stop it?

Answer: That really wouldn’t be relevant to this argument because all that would show is that the Christian God isn’t the true God. The God of the Bible isn’t the real God; the real God is this maximally great being which has been distorted by the Christian religion or something of that sort. So we are not arguing for the God of the Bible, we are arguing here for the notion of the greatest conceivable being. If you don’t like that notion of omnibenevolence, let’s just substitute “morally perfect” for that.

Followup: I do like it. I think he is, but these are questions people have.

Answer: Right, but those questions are not relevant to this argument. Those questions are relevant to whether or not the God of the Bible is maximally great. That will be discussed when we get to things like the problem of evil and suffering and things of that sort.

Alvin Plantinga’s Version

With those concepts in mind, here is Plantinga’s argument:

1. It is possible that a maximally great being (God) exists.

2. If it is possible that a maximally great being exists, then a maximally great being exists in some possible world. (Why? Because that is just what it means to be possible.)

3. If a maximally great being exists in some possible world, then it exists in every possible world. (Why? Because that is the way maximal greatness is defined. Maximal greatness means you have maximal excellence in every possible world.)

4. If a maximally great being exists in every possible world, then it exists in the actual world. (Why? Remember we said earlier that the actual world is one of the possible worlds, namely, it is the one possible world that is actual. So if he exists in every possible world, then he exists in the actual world.)

5. If a maximally great being exists in the actual world, then a maximally great being exists.

6. Therefore, a maximally great being exists.


Question: For #1, it says it is possible. OK, possibly. But the second one says it does exist, is that correct?

Answer: No, notice what it says. It says it exists in some possible world.

Followup: OK, but it does exist in some possible world. I am lost because I do not understand if it possibly exists, why then does it exist? Just because it is possible, what makes it happen?

Answer: It is because that is what we defined “possibly true” to mean. Remember I said, when we say that something is possibly true, like Hillary Clinton is the President of the United States, that just means there is a possible description of reality that could be true that has that proposition as part of the description. So don’t think of existence in a possible world as some sort of mysterious form of existing somewhere. It just means that that proposition is true in one of these descriptions of the way that the world could be.

Question: It seems this whole argument really rests on #3, and I don’t at the moment see why #3 follows. I think I could buy something similar to #3, which would say “If a maximally great being exists in some possible world, and if that possible world is the actual world, then it exists in every possible world.” As stated, I don’t see why #3 follows.9

Answer: The reason #3 follows is by the definition of “maximal greatness.” Maximal greatness means that it exists in every possible world. So if, in some world, there is a being which is maximally great, then that means that that being exists in all of the worlds. Otherwise, it wouldn’t be true that it is maximally great. So, imagine some other world, say W10. In W10, imagine there is a maximally great being. That means that in W10, if you look out at all the other worlds, that being is in all those other worlds, too. So the very definition of maximal greatness means that if it is in one, it is in all. So the controversial premise is not actually #3. The really controversial premise is #1. That is the controversial premise.

Question: I used to have trouble with this, but now I think I understand this. Let me phrase it my way and tell me if I understand it correctly. The reason why #3 follows is because if there is a possible world where there is a being possessing qualities like omnipotence, omnibenevolence, etc. but this being exists in only one possible world (not every possible world), then that would not be a maximally great being. It would only be one possibility. If we say there is one that possesses these qualities in one possible world, we can say that is an excellent being. If it is in three worlds, it is more excellent. If it is in all possible worlds, then it is maximally great.

Answer: Yes, that is exactly right! Imagine you have possible worlds. And let’s imagine that in one of them, there is a maximally great being. As you said, to be maximally great means he has maximal excellence in every possible world. So that means it must exist in all of them. So it is either all or nothing. If the being is maximally great, he can’t just exist in one world, or it wouldn’t be maximally great. The definition entails that it must be in all of them.

Followup: Am I correct in saying that a maximally great being is equivalent to a necessary being?

Answer: Not equivalent, but it entails his necessary existence. He is not just necessary, he is also omnipotent, omniscient, morally perfect, and all the rest. But it would imply he has necessary existence.

Followup: So a maximally great being cannot not exist.

Answer: Right! See, that is what Anselm said. He said once you understand the concept of God, you can see that God cannot not exist. That is what the atheist is going to have to say, is that premise #1 is false.

Let me wrap up by saying that contrary to expectation, steps (2) to (6) in this argument are really uncontroversial. Steps (2) to (6) just follow by definition. What is really controversial is premise #1 – is it possible that God exists? We need to look at what warrant exists for thinking that the existence of God is possible.10


1 5:16

2 10:08

3 A formal definition of modality can be worded as follows: “a classification of propositions on the basis of whether they claim necessity or possibility or impossibility”

4 15:17

5 20:03

6 This material has actually now been published as both a student workbook and teacher handbook. See William Lane Craig and Joseph Tang, The Defense Never Rests: A Workbook for Budding Apologists (CreateSpace, 2011) and William Lane Craig and Joseph Tang, The Defense Never Rests: Teacher’s Handbook (CreateSpace, 2011)

7 25:03

8 30:01

9 34:57

10 Total Running Time: 38:50