William Lane Craig CV


Existence of God (part 14)

Transcript of William Lane Craig's Defenders 2 class.

Excursus: Natural Theology
ยง III. Teleological Argument
Lecture 1

We have been talking about arguments for God’s existence. We have just finished the Kalam Cosmological Argument, and are now going to discuss the Teleological Argument.

Let’s take a step back and get the big picture of where we are. We began the survey of Christian doctrine with the Doctrine of Revelation. Then we moved to the Doctrine of God, and we first had a lengthy examination of the attributes of God, in which we talked about what God is like. Then we began a section on what is called Natural Theology, which explores what we can know about the existence and nature of God apart from divine revelation in Scripture but through human reflection and human reason alone.

In our excursus on Natural Theology that we have embarked upon, we first looked at the Contingency Argument for God’s existence that G. W. Leibniz defended. Then after the Contingency Argument we looked at the KalamCosmological Argument, which has a rich Jewish and Muslim history as well as a Christian background. Having now completed the Kalam Cosmological Argument, we are ready to turn to our new argument, which is the Teleological Argument.


This comes from the Greek word “telos” which means “purpose” or “end” or “goal.” This is the famous argument for design – it is an argument for a cosmic Designer of the world. This is one of the oldest arguments for God’s existence. The ancient Greek philosophers Plato and Aristotle each defended versions of the Teleological Argument. According to Plato, there are two things that lead people to believe in God: the argument from the existence of the soul, which we have not looked at, and then, he said, the argument from “the order of the motion of the stars and of all things under the dominion of the mind which ordered the universe.” Plato referred to this mind that orders the cosmos as “the maker and father of all,” “the King,” who is the source of the rational cosmos in which we live.

His pupil Aristotle has an even more splendid statement of the argument for design. Aristotle imagined what it would be like if there were a race of men who lived underground all their lives in a cave and who suddenly, through an earthquake or something, managed to escape and come out and see the external world. This is how Aristotle describes the impact that seeing the world would have upon these men:

When thus they would suddenly gain sight of the earth, seas, and the sky; when they should come to know the grandeur of the clouds and the might of the winds; when they should behold the sun and should learn its grandeur and beauty as well as its power to cause the day by shedding light over the sky; and again, when the night had darkened the lands and they should behold the whole of the sky spangled and adorned with stars; and when they should see the changing lights of the moon as it waxes and wanes, and the risings and settings of all these celestial bodies, their courses fixed and changeless throughout all eternity – when they should behold all these things, most certainly they would have judged both that there exist gods and that all these marvelous works are the handiwork of the gods.1

In his book The Metaphysics, Aristotle goes on to argue that there must be one, First, Uncaused Cause, a Prime Mover, a First, Uncaused Cause which he refers to as “God” – “a living, intelligent, immaterial, eternal and most good being” who is the source of order in the cosmos.2

As you read the works of these ancient Greek philosophers like Plato and Aristotle you cannot help but think of Paul’s letter to the church in Rome, where in Romans 1:20 he says, “ever since the creation of the world, God’s invisible nature, namely, his eternal power and deity has been clearly perceived in the things that have been made.”3 From the earliest times, men who were totally ignorant of biblical revelation have looked at the order and beauty in nature and inferred that there must be a designer and God who has created the universe.

The Fine-Tuning of the Universe

Today many astronomers are coming to a similar conclusion. Scientists used to think that, whatever the initial conditions of the universe might have been, eventually, given enough time and some luck, intelligent creatures like us would evolve somewhere in the cosmos. But, in fact, as a result of discoveries over the last 40 or 50 years, what has happened is that we now know that that assumption was wrong. In fact, the exact opposite turns out to be true. What astronomers have discovered is that the initial conditions of the universe in the Big Bang had to be finely tuned to a precision and delicacy that literally defies human comprehension if intelligent life forms are to evolve anywhere in the cosmos.

This delicate balance of initial conditions present in the Big Bang has come to be known as the “fine tuning of the universe.” From its earliest inception, the universe appears to be fine tuned for the existence of intelligent life with a precision and delicacy that are literally incomprehensible. There are two kinds of fine tuning. The first involves what are called the constants of nature, and the second involves certain arbitrary quantities that characterize the universe. Let me say a word about each of these.

Constants of Nature

First, the constants of nature. What is a constant? When the laws of nature are expressed as mathematical equations, you find appearing in them certain symbols which stand for unchanging quantities. For example, the force of gravity – the gravitational constant. Or the electromagnetic force. Or the subatomic weak force. Take Newton’s gravitational law. To calculate gravitational force, you take the gravitational constant G, and you multiply this by the masses of the two bodies that are attracting each other. If you have two masses, say, m1 and m2, to figure out the gravitational force between them, you take the gravitational constant times the mass of those two objects divided by the distance between them squared, which we can symbolize as r2. This can be written as G(m1m2/r2). Of course the masses of the objects may vary. They may be two planets, two billiard balls, or a billiard ball and a planet. Those can vary. The distance obviously varies depending on how far apart the objects are. But G is a constant. It always has the same value.

The values of these constants are not determined by the laws of nature. There could be universes that are governed by exactly the same law – you can have the same force law – , but G could take some other value. The value of G is independent of the law of nature in which it occurs. G could have any of a wide range of values, and the law would still be the same. You would have a different kind of universe, obviously, if you changed the value of G. So you can have universes which are governed by the same law but have different values of the constants. And these universes would look very different from our universe. So the actual value that G has is not determined by the laws of nature. It is independent of the laws of nature. Depending on what value these constants take, the universe will look very different.4

Initial Conditions of the Universe

In addition to these kinds of constants there are also these arbitrary quantities that are just put in as initial conditions on which the laws of nature operate. You have certain initial conditions, and then you apply the laws of nature to them to predict certain outcomes. Because these quantities are arbitrary, they are also not determined by the laws of nature. You could have different initial conditions, and then the laws of nature would predict different outcomes. For example, one quantity would be the amount of thermodynamic disorder, or entropy, in the early universe. You remember when we talked about the second law of thermodynamics, we talked about how it predicts that entropy will increase over time as things become more and more disordered thermodynamically? The amount of entropy is just put in the Big Bang as an initial condition. Then the laws of nature take over and determine how things will develop from there. If the initial quantities had been different, then the universe would look very different today. It would predict the evolution of a quite different universe if you alter the initial conditions.

As I say, initially, and for a long time, scientists thought it doesn’t really matter what the initial conditions and constants were; they could take a wide range of values, and things still might evolve to produce complex life forms. Instead what they have been stunned to discover is that these constants and quantities must all fall into an extraordinarily narrow range of life-permitting values in order for complex life forms to evolve and exist anywhere in the universe. This is what is meant by the term the “fine tuning of the universe.” It refers to the fact that these constants and quantities have to fall into this very narrow range of life-permitting values if life is to exist.

It is important to understand that the term “fine tuning” does not mean “designed.” Otherwise, the argument from fine tuning would be question-begging if you said the universe was fine tuned for our existence and that means it was designed for our existence. No, design is one of the explanations of fine tuning. But fine tuning doesn’t mean designed. It is meant to be a neutral term. Fine tuning just means that the range of life permitting values of these constants and quantities is exquisitely narrow. If the values of these constants and quantities were to be altered by even less than a hair’s breadth, the life-permitting balance would be destroyed, and the universe would be life-prohibiting instead of life-permitting.


Question: Is it safe to say that fine tuning is fact? Is it universally accepted that the universe is fine tuned?

Answer: Yes, I think that this is really uncontroversial among those who understand the term. I will say something more about this and give some examples of fine tuning. But as a neutral term, that is, not a synonym for design, fine tuning is just a fact. It is just a scientific fact that the constants and quantities have to fall into this very narrow range or the universe would not be life-permitting.

Question: It is a little hard to ponder how fine tuning of the constants and the arbitrary quantities can be embedded into a singularity. For example, it is a little hard to imagine how a singularity could have any entropy at all. Have astrophysicists gotten far in how this works?

Answer: No. In fact, what we are talking about here, when I talk about the early universe, I do not mean the singularity. Some of these constants and quantities result from quantum phase transitions that the universe goes through very, very early. You have first this unified theory – some sort of a quantum theory of gravity – in which there are not separate gravitational particles or electromagnetic forces and so on. You just have a unified force. Then you have this so-called “GUT Era”5 where you have a grand unified theory where gravity breaks loose from the other three fundamental forces of nature, and that will then involve this fine tuned gravitational constant. Then you have it break down further into the fundamental forces of nature like gravitation, electromagnetism, the weak force, and the strong force. As the universe goes through these quantum phase transitions, what happens is these finely tuned values just fall out one after another – inexplicably because these are supposed to be indeterminate phase transitions. When I said “from the beginning,” I didn’t mean from the singularity. I meant from the very, very early universe; but in fact they do fall out serially as the universe goes through these phase transitions.

Question: Why the difference between fine tuning and design? Didn’t these constants and these quantities have to be part of a design also?

Answer: We will see that these are not synonymous terms at all. This isn’t just a quantitative difference. There are other explanations for the fine tuning. For example, chance would be one. The Many Worlds hypothesis – there are parallel universes where the constants and quantities take every possible value in some universe. Or some people will try to bite the bullet and say it is physically necessary that the universe exists with these values of the constants and quantities. So there are other explanations for the fine tuning than design, which underlines the fact that it isn’t synonymous with design. Design will be one explanation of the fact that in order for life to evolve and exist in the cosmos, these constants and quantities all have to fall within this very, very narrow range.

Question: Wouldn’t the fact that you can represent these quantities and constants mathematically be evidence for design?

Answer: I do not think that simply the ability to represent them mathematically requires design. For example, take this constant G. Suppose you could show that G could take any of a wide range of values and life would still exist. That wouldn’t really be finely tuned in that case. So it is not just that it can be represented mathematically, but it is the precision of these values for life that is really at issue here.

Question: Victor Stenger says this is not very imaginative. We can only observe our local area of the universe, but we need to contemplate that it is possible these constants could be different in other parts of our own universe. How would you respond?

Answer: These constants and quantities characterize the early universe. These are cosmic values; they are not local to our galaxy or the Earth or our galactic cluster. These are cosmic conditions. Therefore, this completely evacuates of any force an appeal to the size of the universe as an explanation for how life could exist somewhere by chance. These are cosmic conditions that must be present for life to evolve and exist anywhere in the universe. The only way to get around that would be to posit other universes. We will talk about that later on – that is the so called World Ensemble hypothesis or multiverse hypothesis. But when you are just talking about the size of the universe, this argument circumvents that because we are talking about cosmic initial conditions.

Question: I noticed you said “necessary for life;” you don’t say “life as we know it.” Are there other forms of life that could exist?

Answer: I will address that question in a minute, and you are correct and very perceptive to see that. When you say, “life as we know it” people then go, “Oh well, then if the constants and quantities had been different, little green men with pointy ears might have evolved!” – or slime molds or something of that sort. That would be totally misleading.6 It is life that would not exist in this universe if the constants and quantities were different. As we will see, if these constants or quantities are altered even a little, what happens is you wouldn’t even have chemistry or matter, much less planets and stars that could serve as places for life to evolve. That kind of response simply doesn’t understand the catastrophic consequences of altering these constants and quantities.

Followup: Is life defined as some living, breathing, biological form?

Answer: Right; again I will say something more about that in a little bit. But by life, scientists just mean something like this: the ability of an organism to take in energy, metabolize it, and reproduce after its own kind. Anything that can do that is called life. It doesn’t have to be anything of a form familiar to us. It just has to fill that very generic definition of being able to do something of that sort.

Question: Is this particular issue specific to one particular cosmogony, or is it something that basically any cosmogony model needs to address?7

Answer: It is one that any cosmological model needs to address. These finely tuned conditions are independent of whether you are talking about the standard Big Bang model, or an inflationary model, or some ekpyrotic model, or even a steady state model. These conditions are conditions that are necessary for life to exist in the universe.

Let me give some examples of fine tuning because physics abounds with examples of fine tuning. But before I do so, let me give you some numbers to give you a feel for the delicacy of the fine tuning because otherwise the numbers are so large they become meaningless to us. The number of seconds in the history of the universe, from the very beginning of the universe, is about 1017. That is a 1 followed by 17 zeroes. Just an incomprehensible number – but that is the number of seconds in the universe. The number of subatomic particles in the entire known universe is around 1080.

With those numbers in mind, consider the following. The atomic weak force which operates within the nucleus of the atom is so finely tuned that an alteration of even one part out of 10100 would have rendered the universe life-prohibiting. In order to permit life, the weak force has to be fine tuned to one part out of 10100. Similarly, the so called cosmological constant, which drives the acceleration of the universe, has to be fine tuned to within one part out of 10120 in order for the universe to be life- permitting. Here is a real corker: Roger Penrose of Oxford University has estimated that the initial entropy condition – the entropy level of the early universe – has to be fine tuned to one part out of 1010(123) – a number which is so incomprehensible that to call it astronomical would be a wild understatement.

It is not just one of these numbers that must be fine tuned but all of them. So you multiply these probabilities together until our minds are just reeling in incomprehensible numbers. Having an accuracy of even one part out of 1060 would be like having a range the size of the entire visible universe – 20 billion light years across – and in order for life to exist, a randomly thrown dart would have to land in an area one inch square. And that is just one part in 1060! We are talking about numbers that are just unimaginably greater than that.8

These are just some of the examples of fine tuning. The examples of fine tuning are so many and so various that they are unlikely to disappear with the further advance of science. Like it or not, the fine tuning of the universe for life is just a scientific fact which is well-established.


Question: At what number does it cease to be a probability and become a certainty?

Answer: That is a very, very interesting question actually. When do probabilities become so great that you say this is an impossibility? It is meaningless to talk about one chance out of 1010(123). William Dembski is an expert in mathematics and probability theory. He wrote a book called The Design Inference in which he raises this question to try to determine what is a reasonable probability bound. Dembski takes the number 1 chance out of 1080 to be the probability bound beyond which things are impossible. Anything that has a probability that is less than one out of 1080 becomes impossible and will never happen. So that is the bound that Dembski adopts in that book.9

Question: How exactly is that value determined? It seems arbitrary.

Answer: It wasn’t arbitrary. The reason why Dembski picked it is because it is the number of all subatomic particles in the universe, so you couldn’t have any more events, in a sense, than that. Therefore anything that exceeds that in terms of its improbability is, for all intents and purposes, impossible. He bases it on the number of particles in the universe.

Question: (inaudible)

Answer: You are asking if the strong force is fine tuned? I do not recall seeing anything in the literature about the strong force. Not all of these constants and quantities are fine tuned to the same exquisite degree. Some of them have a greater range. For example, gravity doesn’t need to be as finely tuned as the weak force. You could alter the gravitational constant somewhat and still have life. But after a while it would get too strong, and animals would collapse because they could not sustain themselves; their bodies would collapse if gravity gets too strong. If gravity gets too weak, then matter would never coagulate into planets, and everything would just drift apart. So gravity has to have a finely tuned range; but it is not nearly as exquisitely narrow as some of these others. I do not remember where the strong force falls. You might take a look at a book on this question like Barrow and Tipler’s book The Anthropic Cosmological Principle where they discuss these various fundamental forces of physics. I do not think that the strong force is one that is used as a typical illustration of an exquisitely fine tuned constant.10

Question: (inaudible)

Answer: They do talk about that. Barrow and Tipler’s book is primarily a discussion of these constants and quantities, but they also have sections in which they look at the nature of water and the extraordinary properties that water has that enable the universe to be life-permitting. They do talk a little bit about those, but not to the same degree that they talk about the constants of physics. People who are proponents of the Teleological Argument will often go beyond the fine tuning of the cosmos to talk about how special the Earth is as well. You need to have a moon, for example, to create tides. You need to have a Jupiter in your solar system to act as a kind of vacuum cleaner that will pull away meteors, asteroids, and comets to keep them from pummeling Earth and destroying it. You need to be a certain distance from the star in order to have the right heat that permits life without incinerating it, but not be so cold as to prohibit life. There are any number of those things as well. But this argument from fine tuning alone just does an end run around all of that, and it goes right back to the very initial conditions. If this argument works, then all of those other things will simply layer on more improbability and more evidence for design.11


1 Aristotle, On Philosophy

2 5:01

3 Dr. Craig mistakenly referred to this as Romans 1:19

4 10:02

5 15:03

6 20:01

7 A “cosmogony” is defined as a theory of the origin of the universe.

8 25:25

9 Dr. Craig’s memory fails him here; he corrects himself in the next lecture.

10 Robin Collins does list the strong force as an example of a finely tuned constant. See http://home.messiah.edu/~rcollins/Fine-tuning/FINETLAY.HTM (accessed April 11, 2012). In fact, he references Barrow and Tipler’s book when he states, “Calculations indicate that if the strong nuclear force, the force that binds protons and neutrons together in an atom, had been stronger or weaker by as little as 5%, life would be impossible.” This is footnoted with John Leslie, Universes (New York: Routledge, 1989). pp. 4, 35. as well as John Barrow and Frank Tipler, The Anthropic Cosmological Principle (Oxford: Oxford University Press, 1986). p. 322.

11 Total Running Time 31:15

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