William Lane Craig CV


Existence of God (part 1)

Transcript of William Lane Craig's Defenders 2 class.

Excursus: Natural Theology
ยง I. Contingency Argument
Lecture 1

We now want to interrupt our study of Christian doctrine and take a little excursus, a little side trip, to look at some apologetic issues raised by the subject of God’s existence.

Up to this point, what we have been doing might be called “revealed theology.” We have been studying the nature and attributes of God on the basis of his revelation in Scripture. But what I would now like to do for several weeks is what is called “natural theology,” that is to say, arguments and evidence for the existence of God that are not taken from Scripture but are taken from the data of human experience independent of God’s self-revelation in Scripture. Natural theology was once the high point of much of medieval philosophical thought. But since the Enlightenment, natural theology, as a project, has been largely eclipsed until the late 20th century. Now it has started to enjoy a renaissance of interest. One manifestation of this would be the recent Blackwell Companion to Natural Theology, published in Oxford by Blackwell. It contains defenses of some 11 different arguments for God’s existence. Among contemporary philosophers, there is a tremendous movement in natural theology to re-defend and refurbish various arguments for the existence of God. What I would like to do is to look at five such arguments for God’s existence that I have worked on myself and that I find persuasive. I think these are good reasons to believe that God exists.

What Makes For A Good Argument?

Before we begin to do that, however, let me say a word about what makes for a good argument. By an argument, I don’t mean a quarrel or a fight. Rather when philosophers talk about an argument, what they mean is a series of statements, or premises, which logically lead to a conclusion. The arguments that I am going to be giving are deductive arguments. What are the conditions for an argument to be a good deductive one?

First of all, a good argument must obey the rules of logic. That is to say, its conclusion must follow from the premises by the rules of logic. If it doesn’t, then it is not a good argument; the premises don’t prove the conclusion. A good argument would be one in which the conclusion follows from the premises by the rules of logic.

Secondly, the premises need to be true. It is not enough to have good logic; you also need to have true premises. Those are the two conditions for an argument being a “sound” argument. A sound argument will be one that has true premises and obeys the rules of logic. If the premises are true and the argument obeys the rules of logic, then the conclusion will follow necessarily from the premises.

But it is not enough for an argument to be sound. There is one more factor that needs to be included. The premises need, in some way, to be evident to us. They need to be, in some way, supported by the evidence, so that they are not simply true, but we somehow know them to be true or we have good reason to think that they are true. If they are true, but nobody has any idea that they are true, then this isn’t really a good argument. So the third condition that is required is that the premises are more plausible than their opposites or negations. In other words, the premises are more plausibly true than false. That is important because it means that in a good argument, the premises do not need to be certain; you don’t need to have 100% certainty that the premises are true. The premises simply need to be more plausible than their negations. Even if it is just, say, 52% versus 48%, you should go with the one that has the greater plausibility.1 That would be a good argument.

The arguments that I am going to share with you, I believe, meet all three of these conditions. They are logically valid, they have true premises and, I think at least, that the premises are more plausibly true than their negations. You can feel free to disagree with me. Unlike revealed theology, natural theology doesn’t fall from heaven. These arguments are human constructs. I could be wrong. I may have made a mistake. If the argument is unconvincing to you, that is just fine. I think they are good arguments, and I hope you will, too. But feel free to assess them in your own right, and if you think that one fails to meet one of these conditions, then you can say that it is not a good argument.


Question: Isn’t it a problem that the non-believer or atheist doesn’t follow this notion of plausibility but instead puts the test on it that it has to be 100%? If it’s 52% vs 48%, then it’s nothing because it is not 100% certain.

Answer: That is true, that very, very often unbelievers do that. But what you could point out to them is that, insofar as they hold knowledge to that high a standard, they will be sceptical about virtually everything. There is virtually nothing that we know with that kind of certainty. When you think about it, we don’t even have 100% certainty that the external world is real. You could be a brain in a vat of chemicals wired up with electrodes by a mad scientist to think you are here listening to this lecture. The scientist could even be stimulating your brain to think that it would be crazy for you to think that you are a brain in a vat! That kind of standard is simply unrealistic, and the unbeliever doesn’t hold himself to that standard. For example, these sorts of arguments work in everyday life. Here would be an argument: If it is Sunday, the library is closed. It is Sunday. Therefore, the library is closed. That would give you a good reason for not going to try to return your book today to the library, knowing that it is Sunday. And yet it is not absolutely certain that it is Sunday. Maybe somehow you got mixed up on the days, or maybe the library is having a special opening on Sunday. So maybe it is not true that it is closed. So everything that we do is going to be based upon weighing the evidence for and against something and then making a judgment. Rationality would require us to go with the judgment that is the more plausible of the two. It would be irrational to go with the less plausible judgment. We simply need to help the unbeliever to see that this is not something that we are constructing just for arguments for God’s existence. These are general conditions for living life. There is no special pleading about this for natural theology.

Question: Why do you need #2 and #3? It seems that if you got #2 covered, then why do you need more than that?

Answer: Because the premises could be true, but it would be true unbeknownst to you. For example, it may be true that on April 5, 1805, Napoleon Bonaparte spat in a puddle. That could be true, but I have absolutely no idea whether it is true or not. It is not enough just for the premise to be true; you have to have some kind of warrant for believing the premise in order for the argument to be a good one. That’s the idea. Now how much warrant does it need to be? Does it need to be 100% certain? Obviously not; then we would be sceptics about everything โ€“ we couldn’t even live life. Does it need to be plausible? I don’t think it even needs to be plausible. It simply needs to be more plausible than its negation. It needs to be more probably true than false. That would give you warrant for believing that it is true. That would be why you need both of those.2

Question: Restating this, we are setting up what ought to be convincing; we are not going for 100% certainty.

Answer: This is meant to be practical and realistic and has nothing to do with theology. These are just general conditions for a good argument. It can be an argument for having a BBQ, an argument for going to the grocery store, or watching a movie. If our lives are to be guided by reason, then we can’t set the standard so unreasonably high that we don’t have good reasons for doing anything. We need to have realistic standards for rationally guiding what we believe and how we behave. I think this provides that.

Why Is There Something Rather Than Nothing?

With that in mind, let’s turn to the first argument that I would like to talk about, which is a version of the Cosmological Argument for God’s existence. Sometimes this is called the Argument From Contingency. When I was a boy growing up in a little town in Iowa, you could look up at the sky at night and see the stars brightly lit against the black sky. As I would look up at the stars, I had a deep sense inside that all of this had to come from somewhere. As I looked at the universe, I thought, “Why does this exist? Where did it come from? There must be an explanation for why all of this exists.” Therefore, for as long as I can remember, I have always believed in God as the Creator of the universe. It was only many, many years later, as I began to study philosophy, that I discovered that my childish insight was one that is also shared by many of the world’s greatest philosophers. For example, Gottfried Wilhelm Leibniz, who was a prodigious intellect of 17th century Europe โ€“ he was the inventor of infinitesimal calculus and one of the world’s great thinkers โ€“ Leibniz said, “The first question which should rightly be asked is, ‘Why is there something rather than nothing?’” This is the most fundamental question in Leibniz’s view. Why is there something rather than nothing? In other words, why does anything at all exist? Leibniz, like me, came to the conclusion that the answer is to be found, not in the universe of contingent things around us, but rather in God. God exists necessarily and is the explanation for why anything else exists.

We can put Leibniz’s thinking into the form of a very simple argument that goes like this:

1. Every existing thing has an explanation of its existence.

2. If the universe has an explanation of its existence, that explanation is God.

3. The universe is an existing thing.

Now what follows from these simple premises? If everything that exists has an explanation of its existence, as premise 1 states, and the universe exists, as premise 3 states, then it follows that the universe has an explanation of its existence. From that statement, along with premise 2, it therefore follows that:

4. Therefore, the explanation of the existence of the universe is God.

From this very simple argument, we derive the existence of God as the explanation for the existence of the universe. This is a logically airtight argument. That is to say, it obeys the rules of logic. If the premises are true, then the conclusion follows necessarily. It doesn’t matter if you don’t like the conclusion; it doesn’t matter if you have other reasons for thinking the conclusion is false. As long as the premises are true, it follows logically and necessarily that God is the explanation of the existence of the universe. The whole debate comes down to the question, are the premises true? Are they more plausibly true than false?3

Premise 3 is undeniable for anybody who is a sincere seeker after truth. Again, we are not talking about academic scepticism; we are talking about someone who is really wanting to find out the truth about the world. That the universe exists is obviously true. So it comes down to premises 1 and 2. Are premises 1 and 2 more plausibly true or false? If you think they are more plausibly true than false, then this will be a good argument for God’s existence.


Question: In premise 1, doesn’t that still leave open the possibility that the universe exists just because of its own nature?

Answer: Yes, and I will talk about that later on. We will explore that possibility.

Question: With the talk about plausibility, it seems you are avoiding absolute truth. Are you dealing with absolute truth here or not?

Answer: I am dealing with absolute truth in the sense of objective truth. Something is either true or it is false, independent of whether you think so or not. But when I am talking about something being plausibly true, I am talking about what we have good reason to think is true. For example, if Dave were to write some quantum mathematical equation on the whiteboard, it might be true, but we wouldn’t have any idea whether or not that equation is true. We might not have a clue. You can have objective truth but be ignorant of it, and you might say, “Well, if Dave says it’s true, that makes it plausible that it is true because he would not say otherwise, and he is skilled at mathematics. So if he says it is true, that gives me a good reason to think that this is true. Therefore, it is plausibly true.” Obviously, that is not to say that the truth isn’t objective; it is to say you have some plausible reasons for thinking that it is true. Maybe we could reword it: instead of saying, “It is plausibly true,” we can say, “Plausibly, it is true.” That is what I mean. I do not mean to say that it is a different kind of truth. The adverb there, when we say, “Plausibly, it is true,” is modifying the word “is” not the word “true.”

Question: How would you respond to a sceptic that says #2 begs the question?

Answer: We will get to that. I am going to look at the objections to each of these premises and then attempt to answer how the typical atheist would respond to this argument.

Question: I can imagine Richard Dawkins turning up his nose at #2.

Answer: Well, I think you might be surprised at that. I think you might be surprised to learn that Dawkins would likely agree with #2. I will hold off on that.

Question: From the argument’s standpoint, why aren’t #3 and #2 reversed? It looks to me that the sequencing is off.

Answer: Very good question! In an argument, it doesn’t matter what order you present the premises in. So you could start off with premise 3, then present premise 2. The order is irrelevant. I probably did it this way simply because premise 3 is so obviously true that you just kind of throw it in at the end, and the real debate is going to hang on these first two. But the order is irrelevant. The rules of logic will simply say, “From 1 and 3 it follows that 4” or “From 2 and 3 it follows that 5” or something of that sort. It doesn’t matter what order they are in. You just apply the rules to the premises, and you derive your conclusion.4


1 5:10

2 9:55

3 15:41

4 Total Running Time: 21:16