This is the weekly Q & A blog post by our Research Professor in Philosophy, Dr. William Lane Craig. This week's response is the third part of Dr. William Lane Craig's answer to a question that appeared in last week's Q & A blog post; you can view the first part of the response here and the second part of the response here.


Dr. Craig,

Thank you so much again for the spirited and great debates that you participate together with cosmologists. I have to say that I find this arena of Cosmology and God to be a very good ground to keep polishing primarily because when science proves a theory or finds very good evidence of it we come closer and closer to understanding more of that vast amount of matter and energy we can observe.

In any case I wanted to ask you about the latest debate with Sean Carroll. There were some strong points made in that debate that as a layman in cosmology make me want to seek further and further what are the theoretical physicists really saying on their theories. The media is not always clear on separating the cosmologist opinion/belief vs what their theory actually says without bias. So I went ahead and looked at Sean Carroll's post debate comments.

It seems to me that the objections that make me question the way the Kalam argument works as well as what the latest theories are showing vs cosmologists own opinion are Sean's answers to:

  1. First Premise of Kalam Argument (Aristotelean Causation). He digs deep onto Aristotelean analysis of causation being outdated.
  2. Boltzmann Brain problem. He mentions that the BB problem helps isolate those models of multiverses that are not tenable. So what about the models that do work?
  3. Fine Tuning. Sean mentions 5 points about Fine Tuning not being good argument for theism and he goes on and says that you did not respond to them. I understand that on your Q&A 49 you mentioned that the universe is fine-tuned for the existence of intelligent life is a solid fact; so I get confused with what Sean says about "he didn't offer any suggestion that we actually do know the conditions under which life can and cannot form."

Anyways, I hope you can answer this questions for me and help me advance in my pursue to understand modern cosmology, its facts and its hopes. Also, will you also make contact with Allan Guth about the BVG theorem? I find it puzzling that the first one to say you were wrong about BVG was Dr. Krauss and then we saw your e-mail exchange with Valenking proving otherwise. It would be nice to see for us viewers what your interaction would be with Allan Guth, now that Sean Carroll is claiming you are mistaken in the interpretation of the theorem.



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Dr. William Lane CraigDr. William Lane Craig’s Response

Now that the transcript of my debate with Sean Carroll is available, I am able to comment responsibly on the arguments offered in the debate. In last week’s Q & A post and in the post the week before, I addressed Jahir’s first and second questions respectively. Now I turn to his third question about the teleological argument from the fine-tuning of the universe.

Outline of the Argument

Here is an outline of my argument:

Teleological Argument

1. The fine-tuning of the universe is due to either physical necessity, chance, or design.

2. It is not due to physical necessity or chance.

2.1 Fine tuning is not due to Physical Necessity.

2.11 M-theory permits 10500 different universes with various values of the fundamental constants and quantities.

2.2 Fine tuning is not due to Chance.

2.21 Multiverse hypothesis (incl. Carroll’s model) faces Boltzmann Brain problem.

3. Therefore, it is due to design.

The evidence of physical cosmology is relevant to the truth of premise (2), so that is where I spent my time.

Carroll had obviously come prepared with his five objections to the argument from fine-tuning. In a debate situation it is vital, given the time constraints, to determine which objections need to be answered and which may be safely ignored. In our debate I did not try to respond to every one of Carroll’s objections but chose to respond only to those I deemed vital. So let’s see how my argument fares in light of them. I’ll skip my exposition in my opening speech and go straightaway to Carroll’s objections.

First Objection: Denial of Fine-Tuning

Carroll says,

First, I am by no means convinced that there is a fine-tuning problem and, again, Dr. Craig offered no evidence for it. It is certainly true that if you change the parameters of nature our local conditions that we observe around us would change by a lot. I grant that quickly. I do not grant therefore life could not exist. I will start granting that once someone tells me the conditions under which life can exist. What is the definition of life, for example? If it’s just information processing, thinking or something like that, there’s a huge panoply of possibilities. They sound very “science fiction-y” but then again you’re the one who is changing the parameters of the universe. The results are going to sound like they come from a science fiction novel. Sadly, we just don’t know whether life could exist if the conditions of our universe were very different because we only see the universe that we see.

This first objection is actually an objection to premise (1). It does not offer an explanation of fine-tuning but rather denies that fine-tuning exists, so there is nothing to be explained.

Carroll’s claim that I offered no evidence for the fact of fine-tuning is somewhat exaggerated. In my opening speech I said, “Scientists have been stunned by the discovery that the existence of intelligent, interactive life depends upon a complex and delicate balance of fundamental constants and quantities, like the gravitational constant and the amount of entropy in the early universe, which are fine-tuned to a degree that is literally incomprehensible.” Here I explain what fine-tuning is, mention the attitude toward it which is widespread in the scientific community, and give an example of both a fundamental constant and an arbitrary quantity that exhibits fine-tuning. Carroll’s complaint is that we cannot justifiably say that these constants and quantities are finely tuned because we don’t know whether life would still exist were their values altered. The reason he gives for his skepticism is that we see only our universe, not others.

Most scientists are not persuaded by this flat denial of fine-tuning. Therefore, I did not want to waste time on this objection but wanted to get it out of the way quickly so that I could get on to more substantive matters. So in my second speech I simply said, “Here Dr. Carroll expresses skepticism that the fine-tuning is real. But a good many, if not most, of his colleagues would simply disagree with him here. Luke Barnes provides a list of just some of the scientists who have published works in defense of the reality of fine-tuning,” and then I gave Barnes’ impressive list: Barrow, Carr, Carter, Davies, Dawkins, Deutsch, Ellis, Greene, Guth, Harrison, Hawking, Linde, Page, Penrose, Polkinghorne, Rees, Sandage, Smolin, Susskind, Tegmark, Tipler, Vilenkin, Weinberg, Wheeler, Wilczek.[1] The point is that if Carroll wants to deny the fact of fine-tuning, then his bone to pick is not with me but with his colleagues, several of whom are even more eminent in the field.

Then I pointed out that Carroll himself recognizes the fact of fine-tuning, for he points to the universe’s low entropy condition as “an uncomfortable fine-tuning problem” which he tries to explain. Carroll later characterizes my response as a clever “got cha!” move, but it is not that at all. The point rather is, as I explain, that Carroll goes to enormous lengths to explain away the fine-tuning via the World Ensemble, or multiverse, hypothesis. That is to concede the truth of premise (1) and dispute instead the truth of premise (2) by defending the alternative of chance. Carroll will later respond to my point by saying that the fine-tuning in the case of entropy is not for life: life could exist even if the entropy were not so low. What he means by this, I think, is that our local patch of order could be surrounded by a sea of relatively high entropy. This issue comes up again when we get to the question why God would create a universe with an unnecessarily low entropy. So we’ll return to that issue momentarily.

Consider now Carroll’s counter-response to my reply in his second speech:

Dr. Craig brings up the point that people disagree with me. It is true. I attempted to give an argument and not merely an opinion poll. If we’re allowed to take opinion polls, I will poll my fellow cosmologists on whether God had anything to do with creating the universe, and I will win by a landslide. I suspect that Dr. Craig thinks the majority of the opinions of cosmologists is important for some issues but not for others.

This is a silly response. Of course, the opinions of cosmologists are important for some issues but not for others! For they are experts on some questions and not on others. Specifically, they are experts on cosmology and so may speak with some authority to the issue of the reality of fine-tuning; but they are anything but expert when it comes to theology and philosophy (as cosmologists like Krauss and Hawking have made painfully clear). So the fact that fine-tuning is widely recognized as a fact by scientists, even those who deny that God had anything to do with creating the universe, is important expert testimonial evidence for the reality of fine-tuning.

Carroll did give an argument, it’s true, to which I did not respond, namely, that we don’t know if life would exist were the fundamental constants and quantities to be appreciably changed, since we can observe only our universe. But this argument is easy to answer: because fine-tuning concerns only worlds governed by the same laws of nature as ours, but with different values of the constants and quantities, scientists can predict fairly reliably what would happen if those values were to be changed. The results would be catastrophic. In the absence of fine-tuning there wouldn’t even be chemistry, there wouldn’t even be matter, much less stars and planets where life might evolve. By life, scientists mean that property of organisms to take in food, extract energy from it, grow, adapt, and reproduce. And the point is that in order to permit life so-defined the constants and quantities of the universe have to be incomprehensibly fine-tuned. That’s why fine-tuning is widely recognized as a fact of nature. I’m content to rest my case there, but if you want empirical evidence of the reality of fine-tuning take a look at the abundant resources on the topic.[2]

Second Objection: God Doesn’t Need Fine-Tuning

Carroll’s second objection is very curious. He says,

Secondly, God doesn’t need to fine-tune anything. We talk about the parameters of physics and cosmology: the mass of the election, the strength of gravity. And we say if they weren’t the numbers that they were, then life itself could not exist. That really underestimates God by a lot, which is surprising from theists, I think. In theism, life is not purely physical. It’s not purely a collection of atoms doing things like it is in naturalism. I would think that no matter what the atoms were doing God could still create life. God doesn’t care what the mass of the electron is. He can do what he wants. The only framework in which you can honestly say that the physical parameters of the universe must take on certain values in order for life to exist is naturalism.

Now what is this supposed to be an objection to? It is not a defense of physical necessity or chance, mentioned in premise (2). Initially, I thought that this was supposed to be an objection to the alternative of design, aimed at showing its implausibility. But then how is the objection supposed to work? Of course, the theist thinks that God could have miraculously sustained life or perhaps created a universe operating according to different laws of nature which were not fine-tuned. But how does that do anything to subvert the argument? When it is said that were the values of the constants and quantities found in nature to be altered, life would not exist, one is implicitly assuming ceteris paribus conditions—“all else being equal,” that is to say, assuming no miraculous interventions take place. This is, after all, an argument aimed at showing the explanatory inadequacy of naturalism, not at showing that God could have created the universe in only one way.

So ironically, it seems that this objection is really an objection to premise (1): it’s saying that the theist has more options than simply design. So perhaps we should add miracle to the list:

1*. The fine-tuning of the universe is due to either physical necessity, chance, design, or miracle.

Obviously, the inclusion of additional theistic options in premise (1) will be of no help whatsoever to the naturalist! So while I did not respond to this objection in the debate, it seems to me so lame that it can be safely ignored without detriment.

Third Objection: Denial of Fine-Tuning

Carroll’s third objection is essentially a repeat of the first: fine-tuning is merely apparent not real. Carroll says,

The third point is that the fine-tunings you think are there might go away once you understand the universe better. They might only be apparent. There’s a famous example theists like to give, or even cosmologists who haven’t thought about it enough, that the expansion rate of the early universe is tuned to within 1 part in 1060. That’s the naïve estimate, back of the envelope, pencil and paper you would do. But in this case you can do better. You can go into the equations of general relativity and there is a correct rigorous derivation of the probability. If you ask the same question using the correct equations you find that the probability is 1. All set of measure zero of early universe cosmologies have the right expansion rate to live for a long time and allow life to exist. I can’t say that all parameters fit into that paradigm but until we know the answer we can’t claim that they’re definitely finely-tuned.

As already indicated, most scientists do not think that the fine-tuning is merely apparent and will disappear with the advance of physics. This conviction is based on two factors: first, the sheer multiplicity of instances of fine-tuning and, second, the independence of these instances from one another. Ernan McMullin, a prominent philosopher of science, concludes,

It seems safe to say that later theory, no matter how different it may be, will turn up approximately the same. . . numbers. And the numerous constraints that have to be imposed on these numbers. . . seem both too specific and too numerous to evaporate entirely. . . . A dozen or more constraints have been pointed out. . . . Might they all be replaced? . . . It surely seems a very long shot.[3]

The historical pattern has been than when fine-tuning is suppressed at one point, it only gets transferred somewhere else, rather like the stubborn bump in the carpet. For example, appeal to an inflationary era in the early universe to explain the fine-tuning of the universe’s expansion rate merely shifts the fine-tuning to the primordial inflaton field and the coupling parameter linked to the density fluctuations that eventually became our galaxies.

Fourth Objection: Fine-tuning is the Result of Chance

All Carroll’s objections thus far have been somewhat strained attempts to refute premise (1). But now he will defend chance as the best explanation of fine-tuning by appealing to a World Ensemble or multiverse in which our universe appears by chance. This is where the heart of the contemporary controversy over fine-tuning lies. Carroll explains,

Number four, there’s an obvious and easy naturalistic explanation in the form of the cosmological multiverse. People like to worry about the multiverse. It sounds extravagant. I claim the multiverse is amazingly simple. It is not a theory, it is a prediction of physical theories that are themselves quite elegant, small, and self-contained that create universes after universes. There’s no reason, no right that we have, to expect that the whole entire universe look like the conditions we have right now. But more importantly, if you take the multiverse as your starting point you can make predictions. We live in an ensemble and we should be able to predict the likelihoods that conditions around us take different forms.

As I explained in my opening speech, the multiverse explanation of fine-tuning depends crucially on two factors: (i) the existence of a specific type of World Ensemble and (ii) an observer self-selection effect. In the interests of time, I waived a discussion of (i) in order to focus on (ii).

Now as a professional cosmologist Carroll must be aware of how controversial each of these assumptions is, but he conceals this from our audience by his almost cavalier treatment of them. He tries to reduce the extravagance of assumption (i) by saying that it is a prediction of certain physical theories. This is disingenuous. It is not enough for a theory to predict a generic World Ensemble. That Ensemble must be sufficiently large to ensure that finely-tuned universes will appear in them by chance, which is far from obvious if the universe is temporally and spatially finite. Moreover, the worlds must be randomly ordered in both in their fundamental constants and physical quantities in order to ensure that our combination of constants and quantities will appear by chance. Most important, we must have some reason to think that the relevant theory predicting such a special Ensemble is true. But as George Ellis—whom cosmologist Tony Rothman once described to me as “the man who knows more about cosmology than any other man alive”—points out, there is no evidence at all that any such theory is true.[4] It is telling that Carroll passes over the question of what evidence there is in support of (i) in silence. “Obvious and easy,” indeed!

As for assumption (ii), the observer self-selection effect turns out to be explanatorily vacuous in light of the Boltzmann Brain problem. We saw in last week’s Q & A post Carroll’s equally cavalier attempt to brush aside that problem.

Fifth Objection: Inadequacy of the Design Hypothesis

Carroll’s last objection is deemed by him to be the most important:

Fifth, and most importantly, theism fails as an explanation. Even if you think the universe is finely-tuned and you don’t think that naturalism can solve it, theism certainly does not solve it. If you thought it did, if you played the game honestly, what you would say is, “Here is the universe that I expect to exist under theism. I will compare it to the data and see if it fits.” What kind of universe would we expect? I’ve claimed that over and over again the universe we would expect matches the predictions of naturalism not theism. So the amount of tuning, if you thought that the physical parameters of our universe were tuned in order to allow life to exist, you would expect enough tuning but not too much. Under naturalism, a physical mechanism could far over-tune by an incredibly large amount that has nothing to do with the existence of life and that is exactly what we observe. For example, the entropy of the early universe is much, much, much, much lower than it needs to be to allow for life. You would expect under theism that the particles and parameters of particle physics would be enough to allow life to exist and have some structure that was designed for some reason whereas under naturalism you’d expect them to be kind of random and a mess. Guess what? They are kind of random and a mess. You would expect, under theism, for life to play a special role in the universe. Under naturalism, you would expect life to be very insignificant. I hope I don’t need to tell you that life is very insignificant as far as the universe is concerned.

In my opening speech, I concluded my discussion of the teleological argument with the caveat: “Therefore, we ought to prefer the hypothesis of design unless the design hypothesis can be shown to be just as implausible as its rivals. I’ll leave it up to Professor Carroll to present any such objections.” This fifth objection is precisely Carroll’s attempt to do just that. Technically, his objection ought to be to the design hypothesis, not theism, since we have not concluded to theism but to a cosmic Designer. I should argue that theism is considerably more probable given the existence of a Creator and Designer of the universe than it would otherwise be, but that is an additional step in the argument. The question, then, is whether Carroll’s objection makes the design hypothesis as implausible as the hypotheses of physical necessity or chance.

Carroll’s objection is odd in a number of ways. For example, it is no part of the argument from fine-tuning to claim that every constant or quantity which nature exhibits is finely tuned, but just that enough of them are to make the probability of their all falling into the life-permitting range by chance practically impossible. So how is that argument in any way undermined by pointing to a quantity in the universe that is not finely tuned? It’s hard to see the relevance. Moreover, it is not true that the values of the fundamental constants and quantities are “kind of random and a mess.” They all fall into the life-permitting range. It’s just that the life-permitting range of some is broader than it is for others. For example, gravity is fine-tuned to about 1/1031, the weak force to about 1/109, and the proton/neutron mass ratio to about 1/70. So what? So long as they are all life-permitting (or, better, permitting of embodied, conscious agents), what does it matter if the life-permitting range of entropy, for example, is much wider than that of gravity with respect to their assumable ranges? Furthermore, recall that Carroll thinks that the entropy of the universe is, in fact, fine-tuned, but not for life. That leaves it open that the entropy is fine-tuned by the cosmic Designer for something other than life. How will Carroll exclude that? How does he know that the Creator is not like an artist who likes to splash his canvas with extravagant colors and forms? Maybe Carroll’s conception of God is just fundamentally wrong.

Carroll claims that if there were a divine Designer, then he would not have made the entropy of the universe so low as it is, since we could still exist in a higher entropy universe--for example, in an island of order in a sea of high entropy (rather like a Boltzmann Brain!). One might be justifiably skeptical about how Carroll knows what would be in the mind of the Creator of the universe--but leave that aside. Even granted the assumption (which is moot) that the Designer would not make the entropy of the universe lower than it needs to be, Carroll’s argument gratuitously assumes that we on Earth are all the life there is and that the Designer could not have other ends in view in giving the universe its low entropy condition. So in response to Carroll, I replied in my rebuttal,

Dr. Carroll says that theism does no better in accounting for the low entropy condition of the universe. For why, he asks, did God make the entropy of the universe so unnecessarily low in order to create us? Well, I have two responses to this. First, it is no part of the fine-tuning argument to assert that the purpose for which the universe was created is us! There may well be intelligent life created by God scattered throughout the universe. But, secondly, as Robin Collins has pointed out, even if a general low entropy condition is not necessary for our existence, it is necessary for the discoverability of the universe. God hasn’t given us an instruction manual about how the world works. But what he has done is make a world which is susceptible to rational exploration and discovery. And if God wanted to make a universe discoverable by embodied, conscious agents, he might well make it in such a low entropy condition.

My first response targets Carroll’s claim: “The theistic explanation for cosmological fine-tuning asks you to look at this picture and say, ‘I know why it is like that. It’s because I was going to be here or we were going to be here.’ But there is nothing in our experience of the universe that justifies the kind of flattering story we like to tell about ourselves.” Carroll evidently misunderstands fine-tuning to entail that the object for which the universe is fine-tuned is the purpose of the universe. But that’s not right. The universe is fine-tuned for zebras and flatworms as well as human beings, but that does not imply that the purpose for which the universe was created is flatworms! Fine-tuning is a neutral term indicating that the range of values which allows something to exist is exquisitely narrow compared to the range of assumable values. The question of why something is fine-tuned is another question, which the argument from fine-tuning does not address. Specifically, the argument does not claim that the universe is as it is because “we were going to be here.” The Designer might have intended for life to exist at various places in the universe, which requires a general low entropy condition.

My second response targets a claim Carroll has elsewhere made that if God exists, then He would have given us Holy Scriptures containing scientific information about how the world works. What Collins’ view suggests instead is that God wants us to discover those things ourselves and so has made a universe susceptible to scientific inquiry. That requires a general low entropy condition. The purpose of Holy Scripture is, more importantly, to make us wise unto salvation.

In his rebuttal Carroll fails to respond to these two points, as I point out in my closing statement. Rather he responds to something I said outside the context of the debate:

Now Dr. Craig said that we shouldn’t expect to know things about the world simply because we say that God finely-tuned it. “Just because under theism,” he says, “God made the parameters of the universe such to allow life to exist doesn’t mean we can have any other expectation for predicting what those parameters are.” This reflects something that he said on his website earlier. In a similar context he said, “Suppose God is more like the cosmic artist who wants to splash his canvas with the extravagance of design and who enjoys creating this fabulous cosmos designed with fantastic detail for observers.” So, what this attitude is saying is that well, my point is that this is not some sort of sophisticated apologetic strategy. This is an admission of defeat. This is saying we should never expect theism to explain why the universe is one way rather than some other way. You know God—God is an artist. You know artists; they’re kind of quirky and unpredictable. We can’t expect to know what they’re going to do ahead of time. Anything you might possibly observe about the universe, according to this view, I can explain as saying, “That is what God would have done.”

This seems to get things exactly backwards. Consider the artist analogy. Finding a portrait of a person, we infer that it was painted by an artist. The pattern of colors is just too complex to be plausibly the result of chance. A skeptic points to a portion of the background which is slurry and says, “If this picture were painted by an artist, then we wouldn’t expect him to have painted this background so indistinctly. It, too, should have been finely executed.” We would be utterly unconvinced by such a claim, since the artist might well have reasons for having a blurred background. It is the objector who suffers the defeat of his objection.

Now does that mean that anything we might possibly observe on the canvas could justify the explanation, “This was done by an artist”? Of course not! Some works of modern art give no clue to having been the product of intelligent design. Looking at them, we might think, “That could have been executed by a chimpanzee.” But maybe we are, in fact, looking at a Jackson Pollock, which was, indeed, painted by an artist with specific ends in mind. In such a case a design inference would not be justified, even if there were a designer. The problem is that an intelligent agent can deliberately mask his tracks and make something look accidental. This shows that the hypothesis of design can be verifiable even though it is not falsifiable. Carroll’s point is that design of the universe cannot be falsified (which defeats his objection), but he wrongly concludes that we therefore cannot have good grounds for inferring design.

Summing Up

The bulk of our discussion concerning the teleological argument had to do with the Boltzmann Brain objection to the multiverse hypothesis, which I discussed in last week’s Q & A post. Here we have considered Carroll’s five objections to the argument from fine-tuning.

We saw that Carroll’s first and third objections were essentially the same, namely, that the fine-tuning is merely apparent, not real. In response to this objection I simply rested my case on the majority view of scientists like Brandon Carter, Paul Davies, George Ellis, Roger Penrose, Martin Rees, and many others, that the universe is fine-tuned for intelligent life. To deny the fact of fine-tuning is really an act of desperation motivated, I suspect, by the naturalistic desire not to let a theist foot in the door.

The second objection I did not reply to. But it is so evidently misconceived that it plays no significant role in the debate over fine-tuning. It really amounts to nothing more than expanding the theistic explanatory options.

The fourth objection lay at the heart of our debate over fine-tuning. Carroll opts for the explanation of chance rather than physical necessity or design. In order to defend the alternative of chance, he recurs to the hypothesis of a World Ensemble or multiverse. So we are confronted with two competing metaphysical hypotheses for explaining fine-tuning: a World Ensemble or a Cosmic Designer. I explained that the World Ensemble hypothesis relies crucially on (i) the existence of a specific type of World Ensemble and (ii) an observer self-selection effect. Although I made no attempt to challenge (i), neither did Carroll provide any evidence for it. I strongly contested (ii), however, and as we saw in last week’s QoW, Carroll failed to offer substantive, specific evidence in support of his appeal to it. So this objection is not only defeated, but with it falls the last ring of defense of the alternative of chance.

That leaves us with design as the best explanation, unless Carroll can show design to be as implausible as chance. He tried to do so by arguing that the excessively low entropy condition of the universe is improbable given design. But my two replies to this, namely, that life may be scattered throughout the universe and that the Cosmic Designer may have created the universe so as to be, not just habitable, but discoverable by created agents, seem to me very plausible and are in any case admitted by Carroll to defeat his objection. His complaint that this makes the design hypothesis unfalsifiable is of little consequence, since the crucial fact is its verifiability.

This post and other resources are available on Dr. William Lane Craig's website:

Learn more about Dr. Craig’s latest book, A Reasonable Response.

[1] L. A. Barnes, “The Fine-Tuning of the Universe for Intelligent Life,” Publications of the Astronomical Society of Australia 29 (2012): 529–564.

[2] E.g., John D. Barrow and Frank Tipler, The Anthropic Cosmological Principle (N.Y.: Oxford University Press, 1986); John Leslie, Universes (London: Routledge, 1989); Martin Rees, Just Six Numbers (N. Y.: Basic Books, 1999); Robin Collins, “The Teleological Argument: An Exploration of the Fine-Tuning of the Universe,” The Blackwell Companion to Natural Theology, Wm. L. Craig and J. P. Moreland (Oxford: Blackwell, 2009), pp. 202-81.

[3] Ernan McMullin, “Anthropic Explanation in Cosmology,” at “God and Physical Cosmology,” conference at the University of Notre Dame, 2003.

[4] George F. R. Ellis, “Does the Multiverse Really Exist?” Scientific American 305 (August 2011), pp. 38-43.