Richard Dawkins Essay

A Brief Response to The God Delusion by Richard Dawkins

This essay was originally written as a guest post for an agnostic friend's blog.

I'd first like to thank Ben for giving me the opportunity to write this guest post. I'm grateful that the general tenor of this blog is much more respectful than the average Internet discussion. Speaking personally, the arguments raised by this blog have been extremely useful in helping me formulate my faith and clarify the reasons that I am a Christian.

The topic of this post is Richard Dawkins' book The God Delusion which has been hailed as a convincing defense of atheism. Dawkins sets out not only to defend atheism but to portray its worldview as morally and aesthetically pleasing in a way that atheist thinkers of the past (say, Nietzsche) didn't. In fact, the majority of the book is not actually an argument against the existence of God, but rather a polemic against the origins, abuses, and beliefs of religion (in Chapters 1,2,5-10). (At this point, let me briefly apologize to anyone reading this post who, at the hands of professed Christians, has experienced some of the hatred that Dawkins describes. It makes me very ashamed, not of Christ, but of those of us who follow him and bring his name into such ill repute). However, since I have limited space, I've decided to focus only on the rational arguments for atheism since, to rephrase Dawkins: atheism's (or religion's) power to comfort (or offend) doesn't make it true (or false).

Let me focus explicitly on the end of Chapter 4, since Dawkins presents in it what he calls "the central argument of [his] book" (p. 157; all quotations and page numbers are from the 2006 edition). I have tried to take Dawkins' statements in context, but please correct me if you think I've been unfair. His argument is as follows: I'd like to point out two central inconsistencies in this argument. In addition, I'd like to examine whether Dawkins' arguments are purely empirical and derived wholly from scientific evidence and reason, or whether they contain an element of "faith".

First, let's note that Dawkins' argument is essentially one of probability. What Dawkins has attempted to show is not that God's existence is disproved but merely rendered very, very improbable. In the section Irreducible Complexity, Dawkins points out that "Chance is not a solution [to the problem of biological complexity], given the high levels of improbability we see in living organisms, and no sane biologist would ever suggest that it was." (p 119-120) We need to be very careful here. Technically speaking, chance is a possible solution to the problem of biological complexity in the sense that it is physically possible that in 40 million B.C. a random fluctuation of molecules accidentally assembled the entire Eocene ecosystem. In the same way, a hurricane in a factory just might assemble a 747. There are no physical laws that are actually violated by either process (not even the 2nd Law of Thermodynamics; e-mail me later). But what Dawkins is saying is that no scientist in his right mind would believe a theory that depended on such a small probability. In contrast, says Dawkins, natural selection provides an elegant mechanism for the production of complex lifeforms: "natural selection is a cumulative process, which breaks the problem of improbability up into small pieces" (p. 121). In other words, given that some primitive form of life exists, natural selection provides a mechanism which ensures that the development of complex life is, if not guaranteed, at least very very probable.

What about the origin of life? Dawkins freely admits that "in once sense, it is a bigger gap" and that the origin of life may have been an "extremely improbable event" (p. 135). When he has to conjure up odds for the sake of argument, Dawkins throws out a truly improbable number (1 in a billion, p. 138), although he does say later that he "doesn't for a moment believe the origin of life was anywhere near so improbable in practice" (p. 138). Doesn't this mean that complex life existing at all is incredibly improbable? No, says Dawkins, because of the anthropic principle (Dawkins is actually invoking the weak anthropic princinple as opposed to the strong anthropic principle). There are a billion, billion planets in the universe. Even if the chances of life evolving spontaneously on a random planet is one in a billion, that means that there are a billion planets on which life began, and given natural selection, nearly all of them will have evolved complex life. Of course we are on one of the lucky ones, because if we were on one of the unlucky ones, we wouldn't be sitting here wondering why there is life on our planet.

Let me try to summarize Dawkins' argument thus far: given the (weak) anthropic principle, and natural selection, it is not at all surprising (i.e. it is probable) that there is a planet (perhaps many planets) somewhere in the universe which contain complex, sentient life like humans; there is no need to invoke a designer. Now we come to the problem: what Dawkins has presented thus far is not an argument, but a framework. He set out to show that there is a natural and probable explanation for the origin of complex life in the universe. If P is the probability for the existence of sentient life somewhere in the universe, then he claims that P is large (say > 50%), so we need not look for a creator God. According to his argument, P = p * N where p is the probability of spontaneous biogenesis and the subsequent evolution of life on a random planet and N is the number of planets in the universe. Since astronomers and cosmologists tell us that N = 10^20, the final, conclusive step in his argument is to provide an estimate of p and to show that p * N is large. So what is the probability that Dawkins calculates? He doesn't provide one. Although this number is the cornerstone of his argument, he makes absolutely no attempt to calculate it.

Since this number is such a crucial piece of his argument, let's try to estimate it using Dawkins' (admittedly low) number 1/10^9 for the probability of the spontaneous genesis of life on a random planet and his estimate of the number of planets in the universe, 10^20. If these numbers are correct, then the probability that sentient life evolved somewhere in the universe is essentially 100%. But are we missing anything? Later in the chapter, Dawkins mentions that "it may be that the origin of life is not the only major gap in the evolutionary story that is bridged by sheer luck, anthropically justified. For example, my colleague... has suggested that the origin of the eucaryotic cell was an even more ... statistically improbable step than the origin of life. The origin of consciousness might be another major gap whose bridging was of the same order of improbability" (p. 140). But if we take Dawkins at his word, something interesting happens. If -as he suggests- each of those steps were equally unlikely (1/10^9), then the probability of overcoming all three would be 1/10^27. Given that there are 10^20 planets, that leaves only a one in ten million chance that there is any planet, anywhere in the universe that contains sentient life like us.

Let me be clear that I am not a biologist, nor am I claiming that the probability of spontaneous biogenesis is one in a billion or one in a trillion, or any other number (if any molecular biologists are reading this, I would be very interested to know your estimate; I've asked biologists that I know and there doesn't seem to be a consensus). My point is that Dawkins does not provide any number at all because he is taking his argument the wrong way around. If you are trying to prove that P is large and find that P = p * N, the next logical thing to do is to estimate p and N using what we know about physical laws from astronomy and biochemistry (see p. 137). It is a specious argument to instead assert "since we know P is almost 1, we can estimate p." Unfortunately, this is precisely what Dawkins does. On page 140, at the end of his argument about biology, he says "The anthropic principle states that, since we are alive, eucaryotic and conscious, our planet has to be one of the intensely rare planets that has bridged all three gaps". But the anthropic principle (as Dawkins is using it) doesn't exactly say that. It says that we have a certain number (10^18) of planets to work with. If the probability of conscious life evolving spontaneously is greater than 1/10^18, then whatever our theory of biogenesis is, it is a probable one. But conversely, it also says that if the probability is significantly less than 1/10^18, then our theory is very unlikely indeed. It simply does not say "since we're here, we must be a very probable event" (the strong anthropic principle does make this argument, but Dawkins doesn't invoke it, presumably because it undermines his argument that there is a probable, natural explanation for the universe). Dawkins has constructed an elaborate framework, but has left out the final step which is the very crux of his argument.

My central objection to Dawkins' reasoning is essentially this: he has mistaken one of his postulates for a conclusion. What was his postulate? That there IS a natural, probable explanation for the origin of life. If this statement is accepted as a postulate then, and only then, does his reasoning make sense. If there is a natural, probable explanation for the origin of life, then we can assert (indeed, must assert), as Dawkins does, that "our planet has to be one of the intensely rare planets that has bridged all three gaps" (p. 141). However, if we are trying to determine WHETHER there is a natural, probable explanation for life, we certainly cannot use this reasoning. Well, why does Dawkins' believe that there is a natural, probable explanation for life? I assert it is part of his faith in materialism. At this point, this statement might appear a bit excessive, but I believe that further justification emerges when we examine Dawkins' next argument regarding the values of the fundamental physical constants.

Dawkins points out that there are six (although there may be as many as 26) fundamental physical constants, which, if any of them were altered very, very slightly from their current values, would prohibit the existence of a life-supporting universe (usually due to the collapse of the universe within a few attoseconds of the Big Bang). Of course, this presents a similar puzzle as the origins of complex biological life and, in a sense, is a precondition for it: if these constants hadn't lined up and the universe had collapsed, complex life wouldn't exist.

Let's stop for a moment at this point. We have been trying thus far to determine whether or not there is a natural, probable explanation for the existence of complex life somewhere in the universe. Let us assume that Dawkins' argument about biology is correct: natural selection provides a mechanism that explains how otherwise highly improbable-looking evidence (biological life) has a very probable explanation. Dawkins takes great pains to show that the beauty of Darwinian evolution is that it provides such an elegant mechanism, without which the existence of life would be highly suspect. But what if we did not have an elegant theory like natural selection which purported to account for the complexity that we observe? Would not the existence of a finely tuned, complex ecosystem then be highly suspect?

That is precisely the case we find ourselves in when it comes to the fundamental constants. To quote Dawkins in what is a bit of an understatement: "we don't yet have an equivalent crane [i.e. mechanism] for physics" (p. 158). In other words, given our current understanding of the laws of physics, there is no objectively verified theory which explains the coincidence of the fundamental constants. If they were determined by pure chance, then the probability that the universe would have been able to sustain life is ridiculously small (Roger Penrose apparently estimated the probability to be 1 in 10^(10^123) ). I think it is at this point that Dawkins' presuppositions become most apparent. For instance, as far as I'm aware there is not a single piece of experimental evidence for a multiverse (see the recent review of Susskind's book in Nature). In a preface to his treatment of multiverse theory in The Elegant Universe, Brian Greene states that "No one knows if these ideas are right or wrong, and certainly they currently lie on the outskirts of mainstream science" (p. 366). That is not surprising since the infinite universes postulated by multiverse theory are usually tucked away in black holes or in other dimensions where we can't observe them. In the face of no concrete evidence and overwhelmingly negative odds, Dawkins states that "We should not give up hope of a better [mechanism] arising in physics" (p. 158). Perhaps we should not. But again, my objection is not about whether some alternate theory of physics exists that will explain life. My argument is that any belief that such a theory exists rests, as Dawkins says, on "hope" (p. 158), not on evidence.

A fundamental postulate of the materialist (I use the word descriptively, not pejoratively) worldview which Dawkins espouses is that: "everything in the universe can be feasibly explained by natural laws", a statement to which I think Dawkins would readily assent. But is this assertion based on solely on empirical, objective evidence? There is an easy way to find out. Can everything in the universe currently be explained by natural laws, as we now understand them? In the case of physics, at least, the answer is a resounding no. The immediate objection is that we would be able to explain these phenomena if we had the right theory. But how do you know there is such a "right theory"? Such an assertion merely brings us back to the original postulate. The assertion that "at some point in the future, we WILL have a theory of that explains everything" is no more or less evidence-based than the assertion that "at some point in the future, we WILL live on the moon". Both of these statements are plausible; they may even be true. But they certainly are based, at root, on faith. That is, these statements form a set of axiomatic beliefs or presuppositions. We do not derive them from evidence; rather, they are part of our worldview.

Let me be clear that I am not disparaging Dawkins' for having a worldview. I have one too. Everyone has one. You can't do science or mathematics or anything unless you begin with a set of assumptions about the nature of reality. These assumptions may appear very reasonable and almost unavoidable, but it is important to recognize that they are assumptions, not conclusions. I also have deliberately avoided the question of God's existence. I do happen to think that science gives us very clear reasons to question materialistic assumptions and to believe in the God who has revealed himself in the Bible. Historical evidence regarding the life, death, and resurrection of Jesus Christ gives us even more. I also think that Dawkins' philosophical arguments against God's existence (for instance, his statement in Point 3 on page 158 that God is improbable because he is complex) are simply wrong. But for the purposes of this essay, I have limited myself to Dawkins' scientific arguments in order to show that they are not as clear-cut as he claims and that scientific evidence does not necessarily lead us to materialism. Rather, we import materialism, or deism, or theism into our reasoning about evidence.

To restate my central objection, I believe that Dawkins is failing to distinguish between his assumptions and his conclusions. As a result, he is unable to see how much his worldview is coloring his interpretation of the evidence. When it comes to physics (and as a consequence to biology), the evidence we face is a set of fundamental constants which all conspire to permit the existence of life in a manner currently so improbable that it defies description. What is it that makes Dawkins so confident that such a coincidence has a natural explanation? What makes him sure that multiverse theory, or many worlds quantum theory, or a grand unification theory which so far have no objective justification will explain the universe? What makes him certain that, in the end, we will find a solution that does not involve a personal, omnipotent, creator? Faith. A set of basic, presuppositional, axiomatic beliefs through which we evaluate the evidence. Dawkins, like all of us, possesses faith. As human beings, we cannot decide whether to have faith; we can only decide what or whom to put our faith in.


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If anyone reading this essay has questions about it or about Christianity in general, feel free to e-mail me at Neil -AT- Shenvi.org I also highly recommend the book The Reason for God by Tim Keller. It is a phenomenal book. Free sermons treating many of the topics covered by this book can be found here.

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America, founded in secularism as a beacon of eighteenth century enlightenment, is becoming the victim of religious politics, a circumstance that would have horrified the Founding Fathers. The political ascendancy today values embryonic cells over adult people. It obsesses about gay marriage, ahead of genuinely important issues that actually make a difference to the world. It gains crucial electoral support from a religious constituency whose grip on reality is so tenuous that they expect to be 'raptured' up to heaven, leaving their clothes as empty as their minds. More extreme specimens actually long for a world war, which they identify as the 'Armageddon' that is to presage the Second Coming. Sam Harris, in his new short book, Letter to a Christian Nation, hits the bull's-eye as usual:

It is, therefore, not an exaggeration to say that if the city of New York were suddenly replaced by a ball of fire, some significant percentage of the American population would see a silver-lining in the subsequent mushroom cloud, as it would suggest to them that the best thing that is ever going to happen was about to happen: the return of Christ . . .Imagine the consequences if any significant component of the U.S. government actually believed that the world was about to end and that its ending would be glorious. The fact that nearly half of the American population apparently believes this, purely on the basis of religious dogma, should be considered a moral and ¬intellectual emergency.

Does Bush check the Rapture Index daily, as Reagan did his stars? We don't know, but would anyone be surprised?

My scientific colleagues have additional reasons to declare emergency. Ignorant and absolutist attacks on stem cell research are just the tip of an iceberg. What we have here is nothing less than a global assault on rationality, and the Enlightenment values that inspired the founding of this first and greatest of secular republics. Science education - and hence the whole future of science in this country - is under threat. Temporarily beaten back in a Pennsylvania court, the 'breathtaking inanity' (Judge John Jones's immortal phrase) of 'intelligent design' continually flares up in local bush-fires. Dowsing them is a time-consuming but important responsibility, and scientists are finally being jolted out of their complacency. For years they quietly got on with their science, lamentably underestimating the creationists who, being neither competent nor interested in science, attended to the serious political business of subverting local school boards. Scientists, and intellectuals generally, are now waking up to the threat from the American Taliban.

Scientists divide into two schools of thought over the best tactics with which to face the threat. The Neville Chamberlain 'appeasement' school focuses on the battle for evolution. Consequently, its members identify fundamentalism as the enemy, and they bend over backwards to appease 'moderate' or 'sensible' religion (not a difficult task, for bishops and theologians despise fundamentalists as much as scientists do). Scientists of the Winston Churchill school, by contrast, see the fight for evolution as only one battle in a larger war: a looming war between supernaturalism on the one side and rationality on the other. For them, bishops and theologians belong with creationists in the supernatural camp, and are not to be appeased.

The Chamberlain school accuses Churchillians of rocking the boat to the point of muddying the waters. The philosopher of science Michael Ruse wrote:

We who love science must realize that the enemy of our enemies is our friend. Too often evolutionists spend time insulting would-be allies. This is especially true of secular evolutionists. Atheists spend more time running down sympathetic Christians than they do countering ¬creationists. When John Paul II wrote a letter endorsing Darwinism, Richard Dawkins's response was simply that the pope was a hypocrite, that he could not be genuine about science and that Dawkins himself simply preferred an honest fundamentalist.

A recent article in the New York Times by Cornelia Dean quotes the astronomer Owen Gingerich as saying that, by simultaneously advocating evolution and atheism, 'Dr Dawkins "probably single-handedly makes more converts to intelligent design than any of the leading intelligent design theorists".' This is not the first, not the second, not even the third time this plonkingly witless point has been made (and more than one reply has aptly cited Uncle Remus: "Oh please please Brer Fox, don't throw me in that awful briar patch").

Chamberlainites are apt to quote the late Stephen Jay Gould's 'NOMA' - 'non-overlapping magisteria'. Gould claimed that science and true religion never come into conflict because they exist in completely separate dimensions of discourse:

To say it for all my colleagues and for the umpteenth millionth time (from college bull sessions to learned treatises): science simply cannot (by its legitimate methods) adjudicate the issue of God's possible superintendence of nature. We neither affirm nor deny it; we simply can't comment on it as scientists.

This sounds terrific, right up until you give it a moment's thought. You then realize that the presence of a creative deity in the universe is clearly a scientific hypothesis. Indeed, it is hard to imagine a more momentous hypothesis in all of science. A universe with a god would be a completely different kind of universe from one without, and it would be a scientific difference. God could clinch the matter in his favour at any moment by staging a spectacular demonstration of his powers, one that would satisfy the exacting standards of science. Even the infamous Templeton Foundation recognized that God is a scientific hypothesis - by funding double-blind trials to test whether remote prayer would speed the recovery of heart patients. It didn't, of course, although a control group who knew they had been prayed for tended to get worse (how about a class action suit against the Templeton Foundation?) Despite such well-financed efforts, no evidence for God's existence has yet appeared.

To see the disingenuous hypocrisy of religious people who embrace NOMA, imagine that forensic archeologists, by some unlikely set of circumstances, discovered DNA evidence demonstrating that Jesus was born of a virgin mother and had no father. If NOMA enthusiasts were sincere, they should dismiss the archeologists' DNA out of hand: "Irrelevant. Scientific evidence has no bearing on theological questions. Wrong magisterium." Does anyone seriously imagine that they would say anything remotely like that? You can bet your boots that not just the fundamentalists but every professor of theology and every bishop in the land would trumpet the archeological evidence to the skies.

Either Jesus had a father or he didn't. The question is a scientific one, and scientific evidence, if any were available, would be used to settle it. The same is true of any miracle - and the deliberate and intentional creation of the universe would have to have been the mother and father of all miracles. Either it happened or it didn't. It is a fact, one way or the other, and in our state of uncertainty we can put a probability on it - an estimate that may change as more information comes in. Humanity's best estimate of the probability of divine creation dropped steeply in 1859 when The Origin of Species was published, and it has declined steadily during the subsequent decades, as evolution consolidated itself from plausible theory in the nineteenth century to established fact today.

The Chamberlain tactic of snuggling up to 'sensible' religion, in order to present a united front against ('intelligent design') creationists, is fine if your central concern is the battle for evolution. That is a valid central concern, and I salute those who press it, such as Eugenie Scott in Evolution versus Creationism. But if you are concerned with the stupendous scientific question of whether the universe was created by a supernatural intelligence or not, the lines are drawn completely differently. On this larger issue, fundamentalists are united with 'moderate' religion on one side, and I find myself on the other.

Of course, this all presupposes that the God we are talking about is a personal intelligence such as Yahweh, Allah, Baal, Wotan, Zeus or Lord Krishna. If, by 'God', you mean love, nature, goodness, the universe, the laws of physics, the spirit of humanity, or Planck's constant, none of the above applies. An American student asked her professor whether he had a view about me. 'Sure,' he replied. 'He's positive science is incompatible with religion, but he waxes ecstatic about nature and the universe. To me, that is ¬religion!' Well, if that's what you choose to mean by religion, fine, that makes me a religious man. But if your God is a being who designs universes, listens to prayers, forgives sins, wreaks miracles, reads your thoughts, cares about your welfare and raises you from the dead, you are unlikely to be satisfied. As the distinguished American physicist Steven Weinberg said, "If you want to say that 'God is energy,' then you can find God in a lump of coal." But don't expect congregations to flock to your church.

When Einstein said 'Did God have a choice in creating the Universe?' he meant 'Could the universe have begun in more than one way?' 'God does not play dice' was Einstein's poetic way of doubting Heisenberg's indeterminacy principle. Einstein was famously irritated when theists misunderstood him to mean a personal God. But what did he expect? The hunger to misunderstand should have been palpable to him. 'Religious' physicists usually turn out to be so only in the Einsteinian sense: they are atheists of a poetic disposition. So am I. But, given the widespread yearning for that great misunderstanding, deliberately to confuse Einsteinian pantheism with supernatural religion is an act of intellectual high treason.

Accepting, then, that the God Hypothesis is a proper scientific hypothesis whose truth or falsehood is hidden from us only by lack of evidence, what should be our best estimate of the probability that God exists, given the evidence now available? Pretty low I think, and here's why.

First, most of the traditional arguments for God's existence, from Aquinas on, are easily demolished. Several of them, such as the First Cause argument, work by setting up an infinite regress which God is wheeled out to terminate. But we are never told why God is magically able to terminate regresses while needing no explanation himself. To be sure, we do need some kind of explanation for the origin of all things. Physicists and cosmologists are hard at work on the problem. But whatever the answer - a random quantum fluctuation or a Hawking/Penrose singularity or whatever we end up calling it - it will be simple. Complex, statistically improbable things, by definition, don't just happen; they demand an explanation in their own right. They are impotent to terminate regresses, in a way that simple things are not. The first cause cannot have been an intelligence - let alone an intelligence that answers prayers and enjoys being worshipped. Intelligent, creative, complex, statistically improbable things come late into the universe, as the product of evolution or some other process of gradual escalation from simple beginnings. They come late into the universe and therefore cannot be responsible for designing it.

Another of Aquinas' efforts, the Argument from Degree, is worth spelling out, for it epitomises the characteristic flabbiness of theological reasoning. We notice degrees of, say, goodness or temperature, and we measure them, Aquinas said, by reference to a maximum:

Now the maximum in any genus is the cause of all in that genus, as fire, which is the maximum of heat, is the cause of all hot things . . . Therefore, there must also be something which is to all beings the cause of their being, goodness, and every other perfection; and this we call God.

That's an argument? You might as well say that people vary in smelliness but we can make the judgment only by reference to a perfect maximum of conceivable smelliness. Therefore there must exist a pre-eminently peerless stinker, and we call him God. Or substitute any dimension of comparison you like, and derive an equivalently fatuous conclusion. That's theology.

The only one of the traditional arguments for God that is widely used today is the teleological argument, sometimes called the Argument from Design although - since the name begs the question of its validity - it should better be called the Argument for Design. It is the familiar 'watchmaker' argument, which is surely one of the most superficially plausible bad arguments ever discovered - and it is rediscovered by just about everybody until they are taught the logical fallacy and Darwin's brilliant alternative.

In the familiar world of human artifacts, complicated things that look designed are designed. To naïve observers, it seems to follow that similarly complicated things in the natural world that look designed - things like eyes and hearts - are designed too. It isn't just an argument by analogy. There is a semblance of statistical reasoning here too - fallacious, but carrying an illusion of plausibility. If you randomly scramble the fragments of an eye or a leg or a heart a million times, you'd be lucky to hit even one combination that could see, walk or pump. This demonstrates that such devices could not have been put together by chance. And of course, no sensible scientist ever said they could. Lamentably, the scientific education of most British and American students omits all mention of Darwinism, and therefore the only alternative to chance that most people can imagine is design.

Even before Darwin's time, the illogicality was glaring: how could it ever have been a good idea to postulate, in explanation for the existence of improbable things, a designer who would have to be even more improbable? The entire argument is a logical non-starter, as David Hume realized before Darwin was born. What Hume didn't know was the supremely elegant alternative to both chance and design that Darwin was to give us. Natural selection is so stunningly powerful and elegant, it not only explains the whole of life, it raises our consciousness and boosts our confidence in science's future ability to explain everything else.

Natural selection is not just an alternative to chance. It is the only ultimate alternative ever suggested. Design is a workable explanation for organized complexity only in the short term. It is not an ultimate explanation, because designers themselves demand an explanation. If, as Francis Crick and Leslie Orgel once playfully speculated, life on this planet was deliberately seeded by a payload of bacteria in the nose cone of a rocket, we still need an explanation for the intelligent aliens who dispatched the rocket. Ultimately they must have evolved by gradual degrees from simpler beginnings. Only evolution, or some kind of gradualistic 'crane' (to use Daniel Dennett's neat term), is capable of terminating the regress. Natural selection is an anti-chance process, which gradually builds up complexity, step by tiny step. The end product of this ratcheting process is an eye, or a heart, or a brain - a device whose improbable complexity is utterly baffling until you spot the gentle ramp that leads up to it.

Whether my conjecture is right that evolution is the only explanation for life in the universe, there is no doubt that it is the explanation for life on this planet. Evolution is a fact, and it is among the more secure facts known to science. But it had to get started somehow. Natural selection cannot work its wonders until certain minimal conditions are in place, of which the most important is an accurate system of replication - DNA, or something that works like DNA.

The origin of life on this planet - which means the origin of the first self-replicating molecule - is hard to study, because it (probably) only happened once, 4 billion years ago and under very different conditions from those with which we are familiar. We may never know how it happened. Unlike the ordinary evolutionary events that followed, it must have been a genuinely very improbable - in the sense of unpredictable - event: too improbable, perhaps, for chemists to reproduce it in the laboratory or even devise a plausible theory for what happened. This weirdly paradoxical conclusion - that a chemical account of the origin of life, in order to be plausible, has to be implausible - would follow if it were the case that life is extremely rare in the universe. And indeed we have never encountered any hint of extraterrestrial life, not even by radio - the circumstance that prompted Enrico Fermi's cry: "Where is everybody?"

Suppose life's origin on a planet took place through a hugely improbable stroke of luck, so improbable that it happens on only one in a billion planets. The National Science Foundation would laugh at any chemist whose proposed research had only a one in a hundred chance of succeeding, let alone one in a billion. Yet, given that there are at least a billion billion planets in the universe, even such absurdly low odds as these will yield life on a billion planets. And - this is where the famous anthropic principle comes in - Earth has to be one of them, because here we are.

If you set out in a spaceship to find the one planet in the galaxy that has life, the odds against your finding it would be so great that the task would be indistinguishable, in practice, from impossible. But if you are alive (as you manifestly are if you are about to step into a spaceship) you needn't bother to go looking for that one planet because, by definition, you are already standing on it. The anthropic principle really is rather elegant. By the way, I don't actually think the origin of life was as improbable as all that. I think the galaxy has plenty of islands of life dotted about, even if the islands are too spaced out for any one to hope for a meeting with any other. My point is only that, given the number of planets in the universe, the origin of life could in theory be as lucky as a blindfolded golfer scoring a hole in one. The beauty of the anthropic principle is that, even in the teeth of such stupefying odds against, it still gives us a perfectly satisfying explanation for life's presence on our own planet.

The anthropic principle is usually applied not to planets but to universes. Physicists have suggested that the laws and constants of physics are too good - as if the universe were set up to favour our eventual evolution. It is as though there were, say, half a dozen dials representing the major constants of physics. Each of the dials could in principle be tuned to any of a wide range of values. Almost all of these knob-twiddlings would yield a universe in which life would be impossible. Some universes would fizzle out within the first picosecond. Others would contain no elements heavier than hydrogen and helium. In yet others, matter would never condense into stars (and you need stars in order to forge the elements of chemistry and hence life). You can estimate the very low odds against the six knobs all just happening to be correctly tuned, and conclude that a divine knob-twiddler must have been at work. But, as we have already seen, that explanation is vacuous because it begs the biggest question of all. The divine knob twiddler would himself have to have been at least as improbable as the settings of his knobs.

Again, the anthropic principle delivers its devastatingly neat solution. Physicists already have reason to suspect that our universe - everything we can see - is only one universe among perhaps billions. Some theorists postulate a multiverse of foam, where the universe we know is just one bubble. Each bubble has its own laws and constants. Our familiar laws of physics are parochial bylaws. Of all the universes in the foam, only a minority has what it takes to generate life. And, with anthropic hindsight, we obviously have to be sitting in a member of that minority, because, well, here we are, aren't we? As physicists have said, it is no accident that we see stars in our sky, for a universe without stars would also lack the chemical elements necessary for life. There may be universes whose skies have no stars: but they also have no inhabitants to notice the lack. Similarly, it is no accident that we see a rich diversity of living species: for an evolutionary process that is capable of yielding a species that can see things and reflect on them cannot help producing lots of other species at the same time. The reflective species must be surrounded by an ecosystem, as it must be surrounded by stars.

The anthropic principle entitles us to postulate a massive dose of luck in accounting for the existence of life on our planet. But there are limits. We are allowed one stroke of luck for the origin of evolution, and perhaps for a couple of other unique events like the origin of the eukaryotic cell and the origin of consciousness. But that's the end of our entitlement to large-scale luck. We emphatically cannot invoke major strokes of luck to account for the illusion of design that glows from each of the billion species of living creature that have ever lived on Earth. The evolution of life is a general and continuing process, producing essentially the same result in all species, however different the details.

Contrary to what is sometimes alleged, evolution is a predictive science. If you pick any hitherto unstudied species and subject it to minute scrutiny, any evolutionist will confidently predict that each individual will be observed to do everything in its power, in the particular way of the species - plant, herbivore, carnivore, nectivore or whatever it is - to survive and propagate the DNA that rides inside it. We won't be around long enough to test the prediction but we can say, with great confidence, that if a comet strikes Earth and wipes out the mammals, a new fauna will rise to fill their shoes, just as the mammals filled those of the dinosaurs 65 million years ago. And the range of parts played by the new cast of life's drama will be similar in broad outline, though not in detail, to the roles played by the mammals, and the dinosaurs before them, and the mammal-like reptiles before the dinosaurs. The same rules are predictably being followed, in millions of species all over the globe, and for hundreds of millions of years. Such a general observation requires an entirely different explanatory principle from the anthropic principle that explains one-off events like the origin of life, or the origin of the universe, by luck. That entirely different principle is natural selection.

We explain our existence by a combination of the anthropic principle and Darwin's principle of natural selection. That combination provides a complete and deeply satisfying explanation for everything that we see and know. Not only is the god hypothesis unnecessary. It is spectacularly unparsimonious. Not only do we need no God to explain the universe and life. God stands out in the universe as the most glaring of all superfluous sore thumbs. We cannot, of course, disprove God, just as we can't disprove Thor, fairies, leprechauns and the Flying Spaghetti Monster. But, like those other fantasies that we can't disprove, we can say that God is very very improbable.

Richard Dawkins is the Charles Simonyi Professor of the Public Understanding of Science at Oxford University. He is a Fellow of the Royal Society, and the author of nine books, including The Selfish Gene, The Blind Watchmaker and The Ancestor's Tale. His new book, The God Delusion, published last week by Houghton Mifflin, is already a NEW YORK TIMES bestseller, and his Foundation for Reason and Science launched at the same time (see RichardDawkins.net).

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