Summary
Does God exist? This is one of the most important questions a person can consider. Your belief in the existence of God has enormous implications on your views of life, humanity, morality, and destiny. In this article, Dr. Craig offers three reasons why life would be meaningless without God and then presents five strong arguments for the existence of God, demonstrating the reasonableness of believing that God exists.
Does God exist? Here are five good reasons to think that God exists:
God makes sense of the origin of the universe.
God makes sense of the fine-tuning of the universe for intelligent life.
God makes sense of objective moral values in the world.
God makes sense of the life, death, and resurrection of Jesus.
God can be immediately known and experienced.
Does God exist? C. S. Lewis once remarked that God is not the sort of thing one can be moderately interested in.
After all, if God does not exist, there's no reason to be interested in God at all.
On the other hand, if God does exist, then this is of paramount interest, and our ultimate concern ought to be how to be properly related to this being upon whom we depend moment by moment for our very existence.
So people who shrug their shoulders and say, "Does God exist? What difference does it make?" merely show that they haven't yet thought very deeply about this problem. Even atheist philosophers like Sartre and Camus—who have thought very seriously about this problem—admit that the existence of God makes a tremendous difference for man.
Let me mention just three reasons why it makes a big difference whether God exists.
Three reasons why His existence makes a difference
Reason 1: Life is Ultimately Meaningless Without God
If God does not exist, life is ultimately meaningless. If your life is doomed to end in death, then ultimately it does not matter how you live. In the end it makes no ultimate difference whether you existed or not.
Sure, your life might have a relative significance in that you influenced others or affected the course of history. But ultimately mankind is doomed to perish in the heat death of the universe. Ultimately it makes no difference who you are or what you do. Your life is inconsequential.
Thus, the contributions of the scientist to the advance of human knowledge, the research of the doctor to alleviate pain and suffering, the efforts of the diplomat to secure peace in the world, the sacrifices of good people everywhere to better the lot of the human race—ultimately all these come to nothing.
Thus, if atheism is true, life is ultimately meaningless.
Reason 2: Without God We Live Without Hope
If God does not exist, then we must ultimately live without hope. If there is no God, then there is ultimately no hope for deliverance from the shortcomings of our finite existence.
For example, there is no hope for deliverance from evil. Although many people ask how God could create a world involving so much evil, by far most of the suffering in the world is due to man's own inhumanity to man. The horror of two world wars during the last century effectively destroyed the 19th century's naive optimism about human progress.
If God does not exist, then we are locked without hope in a world filled with gratuitous and unredeemed suffering, and there is no hope for deliverance from evil.
Or again, if there is no God, there is no hope of deliverance from aging, disease, and death. Although it may be hard for you as university students to contemplate, the sober fact is that unless you die young, someday you—you yourself—will be an old man or an old woman, fighting a losing battle with aging, struggling against the inevitable advance of deterioration, disease, perhaps senility. And finally and inevitably you will die. There is no afterlife beyond the grave. Atheism is thus a philosophy without hope.
Reason 3: If God Exists, You Can Know His Love Personally
On the other hand, if God does exist, then not only is there meaning and hope, but there is also the possibility of coming to know God and His love personally.
Think of it!
That the infinite God should love you and want to be your personal friend! This would be the highest status a human being could enjoy!
Clearly, if God exists, it makes not only a tremendous difference for mankind in general, but it could make a life-changing difference for you as well.
Now admittedly none of this shows that God exists. But it does show that it makes a tremendous difference whether God exists. Therefore, even if the evidence for and against the existence of God were absolutely equal, the rational thing to do, I think, is to believe in Him. That is to say, it seems to me positively irrational when the evidence is equal to prefer death, futility, and despair over hope, meaningfulness and happiness.
But, in fact, I don't think the evidence is absolutely equal. I think there are good reasons to believe in God. And today I want to share briefly five of those reasons. Whole books have been written on each of these, so all I have time to do is to present a brief sketch of each argument and then during the discussion time we can go more deeply into any of them that you'd like to talk about.
Does God exist? As travelers along life's way, it's our goal to make sense of things, to try to understand the way the world is. The hypothesis that God exists makes sense out of a wide range of the facts of experience.
God makes sense of the origin of the universe
Have you ever asked yourself where the universe came from? Why everything exists instead of just nothing? Typically atheists have said the universe is just eternal, and that's all.
But surely this is unreasonable. Just think about it a minute. If the universe never had a beginning, that means that the number of past events in the history of the universe is infinite. But mathematicians recognize that the existence of an actually infinite number of things leads to self-contradictions.
For example, what is infinity minus infinity? Well, mathematically, you get self-contradictory answers. This shows that infinity is just an idea in your mind, not something that exists in reality. David Hilbert, perhaps the greatest mathematician of the twentieth century, states, the infinite is nowhere to be found in reality. It neither exists in nature nor provides a legitimate basis for rational thought. The role that remains for the infinite to play is solely that of an idea.
But that entails that since past events are not just ideas, but are real, the number of past events must be finite. Therefore, the series of past events can't go back forever; rather the universe must have begun to exist.
This conclusion has been confirmed by remarkable discoveries in astronomy and astrophysics.
In one of the most startling developments of modern science, we now have pretty strong evidence that the universe is not eternal in the past but had an absolute beginning about 13 billion years ago in a cataclysmic event known as the Big Bang. What makes the Big Bang so startling is that it represents the origin of the universe from literally nothing. For all matter and energy, even physical space and time themselves, came into being at the Big Bang.
As the physicist P. C. W. Davies explains, "the coming into being of the universe, as discussed in modern science . . . is not just a matter of imposing some sort of organization . . . upon a previous incoherent state, but literally the coming-into-being of all physical things from nothing."
Of course, alternative theories have been crafted over the years to try to avoid this absolute beginning, but none of these theories has commended itself to the scientific community as more plausible than the Big Bang theory.
In fact, in 2003 Arvind Borde, Alan Guth, and Alexander Vilenkin were able to prove that any universe which is, on average, in a state of cosmic expansion cannot be eternal in the past but must have an absolute beginning. Vilenkin pulls no punches:
It is said that an argument is what convinces reasonable men and a proof is what it takes to convince even an unreasonable man. With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape, they have to face the problem of a cosmic beginning.
That problem was nicely captured by Anthony Kenny of Oxford University. He writes, "A proponent of the Big Bang theory, at least if he is an atheist, must believe that the universe came from nothing and by nothing."
But surely that doesn't make sense!
Out of nothing, nothing comes. So why does the universe exist instead of just nothing? Where did it come from? There must have been a cause which brought the universe into being.
We can summarize our argument thus far as follows:
Whatever begins to exist has a cause.
The universe began to exist.
Therefore, the universe has a cause.
Given the truth of the two premises, the conclusion necessarily follows.
From the very nature of the case, this cause must be an uncaused, changeless, timeless, and immaterial being which created the universe. It must be uncaused because we've seen that there cannot be an infinite regress of causes. It must be timeless and therefore changeless—at least without the universe—because it created time. Because it also created space, it must transcend space as well and therefore be immaterial, not physical.
Moreover, I would argue, it must also be personal. For how else could a timeless cause give rise to a temporal effect like the universe? If the cause were a mechanically operating set of necessary and sufficient conditions, then the cause could never exist without the effect.
For example, the cause of water's freezing is the temperature's being below 0˚ Centigrade. If the temperature were below 0˚ from eternity past, then any water that was around would be frozen from eternity. It would be impossible for the water to begin to freeze just a finite time ago. So if the cause is permanently present, then the effect should be permanently present as well. The only way for the cause to be timeless and the effect to begin in time is for the cause to be a personal agent who freely chooses to create an effect in time without any prior determining conditions.
For example, a man sitting from eternity could freely will to stand up. Thus, we are brought, not merely to a transcendent cause of the universe, but to its personal Creator. Isn't it incredible that the big bang theory thus confirms what the Christian theist has always believed: that in the beginning God created the universe? Now I put it to you: which makes more sense: that the Christian theist is right or that the universe popped into being uncaused out of nothing? I, at least, have no trouble assessing these alternatives!
God makes sense of the fine-tuning of the universe for intelligent life.
During the last 40 years or so, scientists have discovered that the existence of intelligent life depends upon a complex and delicate balance of initial conditions given in the Big Bang itself. Scientists once believed that whatever the initial conditions of the universe, eventually intelligent life might evolve. But we now know that our existence is balanced on a knife's edge. The existence of intelligent life depends upon a conspiracy of initial conditions which must be fine-tuned to a degree that is literally incomprehensible and incalculable.
This fine-tuning is of two sorts.
First, when the laws of nature are expressed as mathematical equations, you find appearing in them certain constants, like the gravitational constant. These constants are not determined by the laws of nature. The laws of nature are consistent with a wide range of values for these constants.
Second, in addition to these constants there are certain arbitrary quantities which are just put in as initial conditions on which the laws of nature operate, for example, the amount of entropy or the balance between matter and anti-matter in the universe. Now all of these constants and quantities fall into an extraordinarily narrow range of life-permitting values. Were these constants or quantities to be altered by a hair's breadth, the life-permitting balance would be destroyed and life would not exist.
For example, the physicist P. C. W. Davies has calculated that a change in the strength of gravity or of the atomic weak force by only one part in 10100 would have prevented a life-permitting universe. The cosmological constant which drives the inflation of the universe and is responsible for the recently discovered acceleration of the universe's expansion is inexplicably fine-tuned to around one part in 10120.
Roger Penrose of Oxford University has calculated that the odds of the Big Bang's low entropy condition existing by chance are on the order of one out of 10 10 (123). Penrose comments, "I cannot even recall seeing anything else in physics whose accuracy is known to approach, even remotely, a figure like one part in 1010 (123)." [5] And it's not just each constant or quantity which must be exquisitely finely-tuned; their ratios to one another must be also finely-tuned. So improbability is multiplied by improbability by improbability until our minds are reeling in incomprehensible numbers.
Now there are three possibilities for explaining the presence of this remarkable fine-tuning of the universe: physical necessity, chance, or design.
The first alternative holds that there is some unknown Theory of Everything (T.O.E.) which would explain the way the universe is. It had to be that way, and there was really no chance or little chance of the universe's not being life-permitting.
By contrast, the second alternative states that the fine-tuning is due entirely to chance. It's just an accident that the universe is life-permitting, and we're the lucky beneficiaries. The third alternative rejects both of these accounts in favor of an intelligent Mind behind the cosmos, who designed the universe to permit life.
Which of these alternatives is the most plausible?
The first alternative seems extraordinarily implausible. There is just no physical reason why these constants and quantities should have the values they do. As P. C. W. Davies states, Even if the laws of physics were unique, it doesn't follow that the physical universe itself is unique. . . . the laws of physics must be augmented by cosmic initial conditions. . . . There is nothing in present ideas about 'laws of initial conditions' remotely to suggest that their consistency with the laws of physics would imply uniqueness. Far from it. . . . . . . it seems, then, that the physical universe does not have to be the way it is: it could have been otherwise.
For example, the most promising candidate for a T.O.E. to date, super-string theory or M-Theory, fails to predict uniquely our universe.
In fact, string theory allows a "cosmic landscape" of around 10500 different universes governed by the present laws of nature, so that it does nothing to render the observed values of the constants and quantities physically necessary.
So what about the second alternative, that the fine-tuning of the universe is due to chance? The problem with this alternative is that the odds against the universe's being life-permitting are so incomprehensibly great that they cannot be reasonably faced. Even though there will be a huge number of life-permitting universes lying within the cosmic landscape, nevertheless the number of life-permitting worlds will be unfathomably tiny compared to the entire landscape, so that the existence of a life-permitting universe is fantastically improbable.
Students or laymen who blithely assert, "It could have happened by chance!" simply have no conception of the fantastic precision of the fine-tuning requisite for life. They would never embrace such a hypothesis in any other area of their lives—for example, in order to explain how there came to be overnight a car in one's driveway.
Some people have tried to escape this problem by claiming that we really shouldn't be surprised at the finely-tuned conditions of the universe, for if the universe were not fine-tuned, then we wouldn't be here to be surprised about it!
Given that we are here, we should expect the universe to be fine-tuned. But such reasoning is logically fallacious. We can show this by means of a parallel illustration.
Imagine you're traveling abroad and are arrested on trumped-up drug charges and dragged in front of a firing squad of 100 trained marksmen, all with rifles aimed at your heart, to be executed. You hear the command given: "Ready! Aim! Fire!" and you hear the deafening roar of the guns. And then you observe that you are still alive, that all of the 100 trained marksmen missed!
Now what would you conclude?
"Well, I guess I really shouldn't be surprised that they all missed. After all, if they hadn't all missed, then I wouldn't be here to be surprised about it! Given that I am here, I should expect them all to miss."
Of course not!
You would immediately suspect that they all missed on purpose, that the whole thing was a set-up, engineered for some reason by someone. While you wouldn't be surprised that you don't observe that you are dead, you'd be very surprised, indeed, that you do observe that you are alive. In the same way, given the incredible improbability of the fine-tuning of the universe for intelligent life, it is reasonable to conclude that this is not due to chance, but to design.
In order to rescue the alternative of chance, its proponents have therefore been forced to adopt the hypothesis that there exists an infinite number of randomly ordered universes composing a sort of World Ensemble or multiverse of which our universe is but a part. Somewhere in this infinite World Ensemble finely-tuned universes will appear by chance alone, and we happen to be one such world. There are, however, at least two major failings of the World Ensemble hypothesis: First, there's no evidence that such a World Ensemble exists. No one knows if there are other worlds. Moreover, recall that Borde, Guth, and Vilenkin proved that any universe in a state of continuous cosmic expansion cannot be infinite in the past. Their theorem applies to the multiverse, too. Therefore, since the past is finite, only a finite number of other worlds can have been generated by now, so that there's no guarantee that a finely-tuned world will have appeared in the ensemble.
Second, if our universe is just a random member of an infinite World Ensemble, then it is overwhelmingly more probable that we should be observing a much different universe than what we in fact observe.
Roger Penrose has calculated that it is inconceivably more probable that our solar system should suddenly form by the random collision of particles than that a finely-tuned universe should exist. (Penrose calls it "utter chicken feed" by comparison. [7]) So if our universe were just a random member of a World Ensemble, it is inconceivably more probable that we should be observing a universe no larger than our solar system.
Or again, if our universe were just a random member of a World Ensemble, then we ought to be observing highly extraordinary events, like horses' popping into and out of existence by random collisions, or perpetual motion machines, since such things are vastly more probable than all of nature's constants and quantities' falling by chance into the virtually infinitesimal life-permitting range.
Observable universes like those are much more plenteous in the World Ensemble than worlds like ours and, therefore, ought to be observed by us. Since we do not have such observations, that fact strongly disconfirms the multiverse hypothesis. On atheism, at least, it is therefore highly probable that there is no World Ensemble.
So once again, the view that Christian theists have always held, that there is an intelligent designer of the universe, seems to make much more sense than the atheistic view that the universe just happens to be by chance fine-tuned to an incomprehensible precision for the existence of intelligent life.
We can summarize this second argument as follows:
The fine-tuning of the universe is due to either physical necessity, chance, or design.
It is not due to physical necessity or chance.
Therefore, it is due to design.
God makes sense of objective moral values in the world.
Does God exist? If God does not exist, then objective moral values do not exist. To say that there are objective moral values is to say that something is right or wrong independently of whether anybody believes it to be so.
It is to say, for example, that Nazi anti-Semitism was morally wrong, even though the Nazis who carried out the Holocaust thought that it was good; and it would still be wrong even if the Nazis had won World War II and succeeded in exterminating or brainwashing everybody who disagreed with them. And the claim is that in the absence of God, moral values are not objective in this sense.
Many theists and atheists alike concur on this point.
For example, the late J. L. Mackie of Oxford University, one of the most influential atheists of our time, admitted: "If . . . there are . . . objective values, they make the existence of a God more probable than it would have been without them. Thus, we have a defensible argument from morality to the existence of a God." [8] But in order to avoid God's existence, Mackie therefore denied that objective moral values exist. He wrote, "It is easy to explain this moral sense as a natural product of biological and social evolution . . . ." Michael Ruse, a philosopher of science, agrees. He explains, Morality is a biological adaptation no less than are hands and feet and teeth. Considered as a rationally justifiable set of claims about an objective something, ethics is illusory. I appreciate that when somebody says "love thy neighbor as thyself," they think they are referring above and beyond themselves. Nevertheless, such reference is truly without foundation. Morality is just an aid to survival and reproduction . . . And any deeper meaning is illusory.
Friedrich Nietzsche, the great 19th century atheist who proclaimed the death of God, understood that the death of God meant the destruction of all meaning and value in life. I think that Friedrich Nietzsche was right. But we must be very careful here. The question here is not: "must we believe in God in order to live moral lives?" I'm not claiming that we must. Nor is the question: "Can we recognize objective moral values without believing in God?"
I think that we can.
Rather the question is: "If God does not exist, do objective moral values exist?" Like Mackie and Ruse, I don't see any reason to think that in the absence of God, human morality is objective. After all, if there is no God, then what's so special about human beings? They're just accidental by-products of nature which have evolved relatively recently on an infinitesimal speck of dust lost somewhere in a hostile and mindless universe and which are doomed to perish individually and collectively in a relatively short time.
On the atheistic view, some action, say, rape, may not be socially advantageous and so in the course of evolution has become taboo; but that does absolutely nothing to prove that rape is really wrong. On the atheistic view, apart from the social consequences, there's nothing really wrong with your raping someone.
Thus, without God there is no absolute right and wrong which imposes itself on our conscience.
But the problem is that objective values do exist, and deep down we all know it. There's no more reason to deny the objective reality of moral values than the objective reality of the physical world. The reasoning of Ruse at best proves only that our subjective perception of objective moral values has evolved. But if moral values are gradually discovered, not invented, then our gradual and fallible apprehension of the moral realm no more undermines the objective reality of that realm than our gradual, fallible perception of the physical world undermines the objectivity of that realm. Most of us think that we do apprehend objective values. As Ruse himself confesses, "The man who says that it is morally acceptable to rape little children is just as mistaken as the man who says, 2+2=5." [11] Actions like rape, torture, and child abuse aren't just socially unacceptable behavior—they're moral abominations. Some things are really wrong. Similarly love, equality, and self-sacrifice are really good. But if objective values cannot exist without God, and objective values do exist, then it follows logically and inescapably that God exists. We can summarize this argument as follows:
If God does not exist, objective moral values do not exist.
Objective moral values do exist.
Therefore, God exists.
God makes sense of the historical facts concerning the life, death, and resurrection of Jesus. The historical person Jesus of Nazareth was a remarkable individual. New Testament critics have reached something of a consensus that the historical Jesus came on the scene with an unprecedented sense of divine authority, the authority to stand and speak in God's place. That's why the Jewish leadership instigated his crucifixion for the charge of blasphemy. He claimed that in himself the Kingdom of God had come, and as visible demonstrations of this fact he carried out a ministry of miracles and exorcisms. But the supreme confirmation of his claim was his resurrection from the dead. If Jesus did rise from the dead, then it would seem that we have a divine miracle on our hands and, thus, evidence for the existence of God. Now most people would probably think that the resurrection of Jesus is something you just accept on faith or not. But there are actually three established facts, recognized by the majority of New Testament historians today, which I believe are best explained by the resurrection of Jesus: His empty tomb, his post-mortem appearances and the origin of the disciples' belief in his resurrection. Let's look briefly at each one of these. Fact #1: Jesus' tomb was found empty by a group of his women followers on Sunday morning. According to Jacob Kremer, an Austrian scholar who has specialized in the study of the resurrection, "by far most scholars hold firmly to the reliability of the biblical statements about the empty tomb." [12] According to D. H. Van Daalen, it is extremely difficult to object to the empty tomb on historical grounds; those who deny it do so on the basis of theological or philosophical assumptions. Fact #2: On separate occasions different individuals and groups saw appearances of Jesus alive after his death. According to Gerd L¸demann, a prominent German New Testament critic, "It may be taken as historically certain that Peter and the disciples had experiences after Jesus' death in which Jesus appeared to them as the risen Christ." [13] These appearances were witnessed not only by believers, but also by unbelievers, skeptics, and even enemies. Fact #3: The original disciples suddenly came to believe in the resurrection of Jesus despite having every predisposition to the contrary. Think of the situation the disciples faced following Jesus' crucifixion: 1. Their leader was dead, and Jewish Messianic expectations included no idea of a Messiah who, instead of triumphing over Israel's enemies, would be shamefully executed by them as a criminal. 2. Jewish beliefs about the afterlife precluded anyone's rising from the dead to glory and immortality before the general resurrection of the dead at the end of the world. Nevertheless, the original disciples suddenly came to believe so strongly that God had raised Jesus from the dead that they were willing to die for the truth of that belief. Luke Johnson, a New Testament scholar at Emory University, states, "Some sort of powerful, transformative experience is required to generate the sort of movement earliest Christianity was." [14] N. T. Wright, an eminent British scholar, concludes, "That is why, as an historian, I cannot explain the rise of early Christianity unless Jesus rose again, leaving an empty tomb behind him." [15] Attempts to explain away these three great facts—like the disciples stole the body or Jesus wasn't really dead—have been universally rejected by contemporary scholarship. The simple fact is that there just is no plausible, naturalistic explanation of these facts. Therefore, it seems to me, the Christian is amply justified in believing that Jesus rose from the dead and was who he claimed to be. But that entails that God exists. We can summarize this argument as follows:
There are three established facts concerning the fate of Jesus of Nazareth: the discovery of his empty tomb, his post-mortem appearances, and the origin of his disciples' belief in his resurrection.
The hypothesis "God raised Jesus from the dead" is the best explanation of these facts.
The hypothesis "God raised Jesus from the dead" entails that the God revealed by Jesus of Nazareth exists.
Therefore, the God revealed by Jesus of Nazareth exists.
God can be immediately known and experienced. This isn't really an argument for God's existence; rather it's the claim that you can know God exists wholly apart from arguments simply by immediately experiencing him. This was the way people in the Bible knew God, as professor John Hick explains: God was known to them as a dynamic will interacting with their own wills, a sheer given reality, as inescapably to be reckoned with as destructive storm and life-giving sunshine . . . They did not think of God as an inferred entity but as an experienced reality. To them God was not . . . an idea adopted by the mind, but an experiential reality which gave significance to their lives. [16] Philosophers call beliefs like this "properly basic beliefs." They aren't based on some other beliefs; rather they are part of the foundation of a person's system of beliefs. Other properly basic beliefs would be the belief in the reality of the past, the existence of the external world, and the presence of other minds like your own. When you think about it, none of these beliefs can be proved. How could you prove that the world was not created five minutes ago with built-in appearances of age like food in our stomachs from the breakfasts we never really ate and memory traces in our brains of events we never really experienced? How could you prove that you are not a brain in a vat of chemicals being stimulated with electrodes by some mad scientist to believe that you are here listening to this lecture? How could you prove that other people are not really androids who exhibit all the external behavior of persons with minds, when in reality they are soulless, robot-like entities? Although these sorts of beliefs are basic for us, that doesn't mean that they're arbitrary. Rather they are grounded in the sense that they're formed in the context of certain experiences. In the experiential context of seeing and feeling and hearing things, I naturally form the belief that there are certain physical objects which I am sensing. Thus, my basic beliefs are not arbitrary, but appropriately grounded in experience. There may be no way to prove such beliefs, and yet it is perfectly rational to hold them. You'd have to be crazy to think that the world was created five minutes ago or to believe that you are a brain in a vat! Such beliefs are thus not merely basic, but properly basic. In the same way, belief in God is for those who seek Him a properly basic belief grounded in our experience of God. We can summarize this consideration as follows:
Beliefs which are appropriately grounded may be rationally accepted as basic beliefs not grounded on argument.
Belief that the biblical God exists is appropriately grounded.
Therefore, belief that the biblical God exists may be rationally accepted as a basic belief not grounded on argument.
Now if this is right, then there's a danger that arguments for the existence of God could actually distract one's attention from God Himself. If you're sincerely seeking God, God will make His existence evident to you. The Bible says, "draw near to God and he will draw near to you" (James 4.8). We mustn't so concentrate on the proofs that we fail to hear the inner voice of God speaking to our heart. For those who listen, God becomes an immediate reality in their lives. Five good reasons to think that God exists We've seen five good reasons to think that God exists:
God makes sense of the origin of the universe.
God makes sense of the fine-tuning of the universe for intelligent life.
God makes sense of objective moral values in the world.
God makes sense of the life, death, and resurrection of Jesus.
God can be immediately known and experienced.
These are only a part of the evidence for God's existence. Alvin Plantinga, one of the world's leading philosophers, has laid out two dozen or so arguments for God's existence. Together these constitute a powerful cumulative case for the existence of God. Therefore, I think that Christian theism is a plausible worldview which commends itself to the thoughtful consideration of every rational human being.
Author, William Lane Craig