In my second post on physicist Sean Carroll’s recent video, Is God a Good Theory?, I’d like to respond to his criticisms of the fine-tuning argument. As we’ll see, Carroll misconstrues the evidence for this argument, leading him to incorrectly conclude that the multiverse hypothesis explains that evidence just as well as the hypothesis that there is a God. Carroll also argues that the early universe’s low (but non-zero) entropy renders the existence of God vanishingly unlikely. I would argue that on the contrary, there is a special reason why the entropy of the early universe has the low, non-zero value it has, and that this can be best explained by the highly plausible hypothesis that God not only wants to make a universe containing intelligent beings, but wants those beings to be aware of His existence.
(Note: This post is a sequel to my earlier post, Is God a good theory? A response to Sean Carroll (Part One).)
The Fine-Tuning Argument: Why God is a Better Explanation than the Multiverse
An artistic depiction of the multiverse. Image courtesy of Silver Spoon and Wikipedia.
In his talk, Professor Carroll declares that he regards the fine-tuning argument as the best argument as the best argument for the existence of God. The question of why the universe is so fine-tuned for life is a valid one. Carroll considers four possible answers:
1. We just got lucky. (This answer strikes Carroll as a cop-out.)
2. Life is more generic than we think: a high proportion of possible universes contain life. (Carroll doesn’t spend much time on this highly speculative proposal, but he notes that in order to refute it, scientists would need to consider all possible theories, cosmologies, and manifestations of life, and then calculate the fraction of universes that could support life. Nobody does this, however, as such a calculation is impractically difficult. I would suggest in passing that Leslie’s “fly on the wall” illustration in his 1989 book, Universes (New York: Routledge) offers a possible way of addressing this problem.)
3. Selection within a multiverse.
So for Carroll, it comes down to: God or the multiverse.
Does Bayes’ theorem favor God or the multiverse?
In order to decide which answer is correct, Professor Carroll turns to Bayes’ Theorem (see here and here, and see here for an intuitive explanation). The theorem can be expressed in this way. Suppose we have a hypothesis H. It might be the hypothesis that God exists. Or, it might be the rival hypothesis that the multiverse exists. Now, some hypotheses are inherently more likely to be true than others. So before we even look at the evidence, we might try to estimate the prior probability of our hypothesis being true. Then we get a piece of evidence E that seems to provide some confirmation for our hypothesis. On Professor Carroll’s account, this evidence is simply the fact that the cosmos contains life. Now we want to quantify how much confirmation the evidence provides for our hypothesis. To calculate that, we first need to figure out how likely we would be to find that evidence, if our hypothesis were true. We also need to know how likely we would be to find that evidence, regardless of whether our hypothesis were true or not. We can then divide the first likelihood by the second, to obtain a number which I’ll call the confirmation factor, C. Basically, it’s a measure of how much more likely to be true the evidence renders our hypothesis. Using Bayes’ Theorem, we can now calculate the posterior probability that our hypothesis is true, given the evidence. It’s simply the prior probability multiplied by the confirmation factor C.
Putting it in mathematical terms, P(H|E) = P(H) x C = P(H)x(P(E|H)/P(E)),
where P(E|H) is the likelihood of our finding that evidence, if our hypothesis were true, and P(H) is the likelihood of our finding that evidence, regardless of whether our hypothesis were true or not.
According to Carroll, the evidence E for God’s existence is simply the fact that the universe contains life. The two rival hypotheses which have been put forward to explain this evidence are: (i) the hypothesis that God exists and (ii) the hypothesis that our universe is just one of countlessly many, inside a larger multiverse. Let’s call these hypotheses H1 (God) and H2 (the multiverse).
To prove that God is a better explanation than the multiverse, we need to do one of two things, according to Carroll. Either we need to show that God’s existence is inherently more likely in the first place than the likelihood of there being a multiverse (or in mathematical terms, the prior probability of H1 is greater than that of H2), or we need to show that the existence of life provides greater confirmation for the hypothesis that there is a God than it does for the hypothesis that there is a multiverse. Let’s look at each of these in turn.
How does the prior probability of God stack up against that of the multiverse?
Carroll argues that we should give a higher prior probability to theories that seem more powerful, simple or elegant. I have already critiqued this claim in my post, Does scientific knowledge presuppose God?, where I argued that the prior expectation that simple theories are more likely to be true is unwarranted, unless we assume the existence of a God Who favors simplicity. Nevertheless, I was prepared to accept a restricted version of this claim: theories which invoke only a few entities in order to explain the facts are more likely to be true than theories which invoke a lot of entities. This is what Occam’s razor states.
Carroll then proceeds to compare the inherent plausibility of the two rival hypotheses: God and the multiverse. Carroll realizes that for many people, the existence of God makes a lot more sense than the multiverse hypothesis. In the first place, it seems much more plausible to believe in one God than in a multiverse containing a very large number – at least 10^500, and perhaps an infinite number – of universes. Hence the prior probability of the multiverse is very low. And in the second place, the striking fact that our universe contains life is more probable given God’s existence than it would be otherwise. In other words, what I’ve called the “confirmation factor” is higher for the God hypothesis than for the multiverse hypothesis. So, it seems that God wins hands-down. Right?
Not so fast, says Professor Carroll. First, he criticizes the common view that the prior probability of the multiverse hypothesis is very low, by pointing out that the multiverse is not, strictly, speaking, a theory, but an entailment of other theories. The laws of physics, he says, predict the existence of many other universes. String theory plus inflation, when taken together, automatically imply the existence of a multiverse. Thus although the hypothesis that there exist zillions of other universe appears wildly extravagant at first sight, Carroll argues that it isn’t, since its existence follows automatically from just a small number of physical principles.
So, what’s the prior probability of the multiverse? Carroll doesn’t attempt to answer this question, but he insists it’s certainly much more than 1 in 10^500. (I should point out, however, that there’s currently no scientific evidence for the string theory which, along with inflation, is said to imply the existence of the multiverse: for the time being, string theory remains a bold but speculative hypothesis.)
Finally, Carroll points out that while we have some grasp of the multiverse, we have no grasp whatsoever of the concept of God. Carroll contends that whereas the multiverse is at least a natural concept that we can get our heads around, the concept of God belongs in a different metaphysical category, of which we know nothing. Hence, he reasons, the multiverse is preferable as an explanation of reality.
Carroll concludes that as ontologically extravagant as the multiverse may appear to be with its vast number of universes, the God hypothesis is much more problematic. In other words, the prior probability of the multiverse, according to Carroll, is actually higher than the prior probability of God.
Which hypothesis is better confirmed by the existence of life: God or the multiverse?
Next, Carroll disputes the assumption that the existence of God renders the occurrence of life in the universe more probable. He points out that if there were an infinite number of universes, then somewhere out there in the multiverse, there would be life. So the probability of life, given the multiverse, is 1. Carroll is prepared to grant that the probability of life, given the existence of God, is also 1: he can’t imagine God creating a lifeless cosmos. So the fact that there’s a universe that supports life is equally probable under either the God hypothesis or the multiverse hypothesis. It doesn’t confirm the existence of God.
Does the multiverse make the problem of God go away? What one physicist thinks
Professor Paul Davies, of the University of Arizona. Image courtesy of Tom Story, Arizona State University and Wikipedia.
Before I go on, I’d just like to point out that the multiverse hypothesis preferred by Dr. Carroll is just as “theological” as the hypothesis that there is a God. In order to illustrate why, I’d like to quote a short passage from the highly esteemed physicist Professor Paul Davies, of Arizona State University, author of the acclaimed best-sellers, God and the New Physics and The Mind of God:
For a start, how is the existence of the other universes to be tested? To be sure, all cosmologists accept that there are some regions of the universe that lie beyond the reach of our telescopes, but somewhere on the slippery slope between that and the idea that there are an infinite number of universes, credibility reaches a limit. As one slips down that slope, more and more must be accepted on faith, and less and less is open to scientific verification.
Extreme multiverse explanations are therefore reminiscent of theological discussions. Indeed, invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator. The multiverse theory may be dressed up in scientific language, but in essence it requires the same leap of faith.
At the same time, the multiverse theory also explains too much. Appealing to everything in general to explain something in particular is really no explanation at all. To a scientist, it is just as unsatisfying as simply declaring, “God made it that way!”
Problems also crop up in the small print. Among the myriad universes similar to ours will be some in which technological civilizations advance to the point of being able to simulate consciousness. Eventually, entire virtual worlds will be created inside computers, their conscious inhabitants unaware that they are the simulated products of somebody else’s technology. For every original world, there will be a stupendous number of available virtual worlds — some of which would even include machines simulating virtual worlds of their own, and so on ad infinitum.
Taking the multiverse theory at face value, therefore, means accepting that virtual worlds are more numerous than “real” ones. There is no reason to expect our world — the one in which you are reading this right now — to be real as opposed to a simulation. And the simulated inhabitants of a virtual world stand in the same relationship to the simulating system as human beings stand in relation to the traditional Creator.
Far from doing away with a transcendent Creator, the multiverse theory actually injects that very concept at almost every level of its logical structure. Gods and worlds, creators and creatures, lie embedded in each other, forming an infinite regress in unbounded space.
— Paul Davies, A Brief History of the Multiverse, New York Times, 12 April 2003
I’d now like to explain why I think Dr. Carroll misconstrues the fine-tuning argument. This in turn leads him to draw incorrect conclusions regarding the likelihood of God’s existence.
What Carroll gets wrong about the fine-tuning argument
(a) Is the existence of the multiverse inherently more likely than the existence of God?
As we have seen, Dr. Carroll thinks that the multiverse is a much simpler concept than is popularly imagined, making its existence more likely. Additionally, he contends that whereas the multiverse is at least a natural concept that we can get our heads around, the concept of God belongs in a different metaphysical category, of which we know nothing. Hence, he reasons, the multiverse is preferable as an explanation of reality. Putting it mathematically, the priorr probability of the multiverse, according to Carroll, is actually higher than the prior probability of God.
The first point I’d like to make in response is that Caroll nowhere attempts to define the word “natural.” Without a definition of the term, his claim that the multiverse is easier to grasp than the concept of a Transcendent Deity is a mere assertion, devoid of supporting evidence.
In my recent post, Does scientific knowledge presuppose God?, I argued that prescriptive rules are the relevant feature that distinguishes the category of the natural from that of the Supernatural. However, Carroll can hardly use this definition of “natural” without embracing its theistic implications: rules, by definition, presuppose the existence of a Rulemaker, and if the cosmos itself is a rule-governed object, then it must have been created by a Transcendent Rule-maker. So my challenge to Carroll is: can you define the term “natural” in a way that contains no reference to God, either implicitly or explicitly?
Second, I would maintain, contra Carroll, that belonging to a separate metaphysical category does not automatically render a Being incomprehensible. All it means is that such a Being is not subject to the limitations that apply to our own metaphysical category. For instance, if prescriptive rules are what distinguishes the category of the natural (as I have argued), then a Transcendent Being is not subject to such prescriptive rules.
Now, if a concept contains built-in limitations, then of course, it cannot be meaningfully applied to a Transcendent Deity. The concept of “walking,” for instance, contains limitations, as it can only be applied to a being that is in one place, but not in another (if it were, it wouldn’t need to walk there), and that has legs, or appendages of some sort. Obviously the concept of “walking” cannot be applied to a Being outside space and time. But the concept of “knowing” or “understanding,” on the other hand, contains no such limitations; nor does the concept of “loving” – or for that matter, the concept of choosing, on the basis of what one knows and loves. The verbs corresponding to these activities are non-modal – a term I shall use for want of a better one – in that they do not specify anything about the manner in which the action is performed – unlike the verb “walk,” which is defined as an activity performed with one’s legs. Hence there is no good reason why verbs like “know,” “love” and “choose” cannot be meaningfully applied to a Transcendent God. Since we know what these verbs mean, and since the nature of God is defined entirely in terms of these non-modal verbs, it follows that the concept of God as a Being Who knows and loves perfectly can be grasped by us, even though the unrestricted manner of God’s knowing and loving cannot.
Third, Carroll’s reasoning can be turned on its head, as physicist Professor Paul Davies argued in the passage quoted above:
There is no reason to expect our world — the one in which you are reading this right now — to be real as opposed to a simulation. And the simulated inhabitants of a virtual world stand in the same relationship to the simulating system as human beings stand in relation to the traditional Creator.
If someone wants to argue that the existence of a Transcendent Being outside our cosmos has a likelihood of zero, then by the same token, doesn’t it follow that the probability of there existing some aliens in an unobservable “multiverse” who created our observable universe would also be zero?
Finally, I would argue that in any case, we don’t need to show that the prior probability of God’s existence exceeds that of the multiverse. All we need to do is show that the prior probability of God’s existence exceeds some minimum threshold – let’s call it 1 divided by N, where N is some very, very large number. If we can then show (as I’ll attempt to do below) that the fine-tuning of the cosmos makes the existence of God N times more likely than the existence of the multiverse (or more precisely, that it confirms God’s existence over that of the multiverse by a factor of N), then that cancels out the low prior probability of God’s existence. And if we can show that the fine-tuning of the cosmos confirms the God hypothesis over the multiverse by a factor far, far greater than N, then we have demonstrated that the existence of God is far more likely than the rival multiverse hypothesis, given the evidence from fine-tuning.
I believe that we can indeed establish a minimum threshold of 1 in 10^120 for the prior probability of God’s existence. Seth Lloyd, in his now-famous paper, titled, Computational capacity of the universe (Physics Review Letters 88:237901,2002, DOI: 10.1103/PhysRevLett.88.237901, arXiv:quant-ph/0110141), calculated that the number of events that have occurred in the entire history of the observable universe is no greater than 10^120. Now consider the hypothesis that every event has a natural cause. In the beginning, we might be indifferent between this hypothesis and the rival hypothesis that at least some events have a supernatural cause: after all, we don’t have any evidence one way or the other. The occurrence of a natural event will count in favor of the naturalistic hypothesis. Moreover, the naturalistic hypothesis will be to some extent strengthened with every additional event that takes place without supernatural intervention. For instance, after witnessing 10 such events, we might place the likelihood of a subsequent supernatural intervention at 1 in 11, and after observing 100 naturally occurring events, we would place the likelihood of a supernatural intervention at 1 in 101. If there have been 10^120 events in the history of the cosmos, then it might be rational to place the likelihood of a subsequent supernatural intervention at 1 in 10^120, but definitely no lower than that: that’s as far as the evidence to date can take us. (Please note that I’m being extremely generous here: I’m conceding for argument’s sake that there have been no supernatural acts during the entire history of the cosmos – which runs counter to the human testimony of miracles.) Now suppose that we are asked to evaluate the likelihood of the hypothesis that unbeknownst to us, the very first event in the history of the cosmos – its creation at the Big Bang – was a supernatural act. In view of all the subsequent events that have occurred without supernatural intervention, we might reasonably evaluate the prior likelihood of this hypothesis at 1 in 10^120, but it would be irrational to estimate it at lower than that.
Even this very low likelihood is enough, when combined with the extremely high degree of fine-tuning in the cosmos, for us to be able to demonstrate that the probability of God’s existence, given the fine-tuning we observe, far exceeds the probability of the multiverse. Scientist and Christain apologist Richard Deem, in his lonline article, Evidence for the Fine Tuning of the Universe, summarizes the evidence for fine-tuning in a handy chart, showing, for five cosmic parameters, the maximum deviation from the accepted values, where any further deviation would either prevent the universe from existing now, either because it wouldn’t have any matter, or because it would be unsuitable for any form of life. I’m going to omit the last parameter listed by Deem (the cosmological constant) because as we’ll see below, Dr. Carroll thinks that parameter counts against fine-tuning. The remaining four parameters are as follows: (i) ratio of electrons to protons (maximum deviation = 1 in 10^37); (ii) ratio of electromagnetic force to gravity (maximum deviation = 1 in 10^40); (iii) expansion rate of the universe (maximum deviation = 1 in 10^55); and (iv) mass density of the universe (maximum deviation = 1 in 10^59). Multiply all these factors together, and you get 1 in 10^191, which means that the combined fine-tuning of the cosmos is 10^191.
Time will tell whether the figures Deem cites turn out to be correct. My point, however, is that on the evidence available to us, the exquisite fine-tuning of the cosmos (to a degree of 10^191) is far greater than the biasing factor of 10^120 with which we might handicap the God hypothesis, on account of the supposed lack of observed miracles during the entire history of the cosmos. Multiply 10^(-120) by 10^191, and we can show that even given our initial bias against supernaturalism, the existence of God is 10^71 times more likely than the rival hypothesis of the multiverse, after we take into account the evidence from fine-tuning.
(b) The relevant evidence for God’s existence isn’t the existence of life, but the discovery of fine-tuning
Infra-red night goggles. Image courtesy of Wikipedia.
In an article entitled, Fine-Tuning and the Infrared Bull’s-Eye (which I blogged about here), philosopher John T. Roberts identifies a vital flaw in the way that the fine-tuning argument is commonly presented. The argument proceeds as if we already know that fine-tuning is required for any sort of life to exist, and then suddenly discover that (surprise!) our own universe contains life. In reality, we already know that life exists in our universe; the surprise is the fine-tuning of the constants of Nature.
In the passage below, the letter L refers to the proposition that Life exists in our universe, while the letter V refers to the proposition that in our universe, the Value of each physical parameter lies within the corresponding range required for life. Both propositions are pretty obvious: after all, if either of them were false, we wouldn’t be here. What’s truly surprising is the discovery – which Roberts represents by the letter R – that fine-tuning is Required for life, or as Roberts puts it, that life is balanced on the head of a pin:
On the standard way of formulating the fine-tuning argument, the fact that fine-tuning is required for life – what I called R – is treated as part of the background knowledge B. L on the other hand (or, on the alternative version, V is treated as the new evidence we are considering. This suggests that we have known all along that fine tuning is required for life to exist in our universe, and then one day we discovered that life does exist in our universe – a striking discovery that forced us to reconsider the case for a designer. Of course, that gets things exactly backwards. We have known all along that our universe is life-sustaining (L). What comes as a surprise and makes us think that maybe we should rethink the matter of chance vs. design is the more recent discovery that fine tuning was required for life.
So, how does Roberts think the argument should be re-formulated, to render it invulnerable to these objections? By making the “surprising” fact the discovery of fine-tuning – symbolized by the letter R – rather than the existence of life (L). The startling discovery of fine-tuning, and not the existence of life, is the evidence that cries out for an explanation. In Roberts’ own words:
This suggests that when we treat the fine-tuning argument as a likelihood argument (or more generally, when we formulate it in Bayesian terms), we should let our background knowledge include L, and let R be the item that plays the role of evidence. After all, the thing that we discovered which suddenly seemed to favor the hypothesis of a designer over the chance hypothesis in a new way was not that there is life in the universe, nor that e.g. the ratio of the strengths of the gravitational and electromagnetic forces has the value it does, but rather that the life we know to exist in the universe depended on a set of conditions balanced on the head of a pin in a way we had never suspected before. So, the crucial move in the argument is this: The precariously-balanced nature of life in our universe is far less surprising given a designer than it would be given chance, and so it evidentially favors design over chance.
Roberts is now ready to put forward his own version of the fine-tuning argument. Before we examine it, there’s just one more principle that we need to be familiar with: the Likelihood Principle. It goes as follows. Suppose you’re considering two rival hypotheses: hypothesis 1 and hypothesis 2. Then we can say that a new piece of evidence E favors hypothesis 1 over hypothesis 2, whenever (and only whenever) the probability of that evidence occurring is higher under hypothesis 1 than it is under hypothesis 2.
Putting it in mathematical jargon: in a context where our background knowledge is B, a piece of evidence E favors hypothesis H1 over hypothesis H2 if and only if the probability of E given hypothesis H1 and background knowledge B, or Pr(E|H1 & B) is greater than the probability of E given hypothesis H2 and background knowledge B, or Pr(E|H2 & B)].
The Likelihood Principle is not at all controversial, philosophically speaking: it simply describes the standard way of adjudicating between rival hypotheses.
Let’s now have a look at Roberts’ formulation of the fine-tuning argument. I’ve translated the steps into layperson’s language, in my bracketed comments:
The fine-tuning argument, then, claims that when our background knowledge includes L (which of course it always does), the discovery of the truth of R evidentially favors design over chance, because R is more likely given design than it is given chance. So here’s how we should reformulate the fine-tuning argument:
Premise 1+: L belongs to our background knowledge B.
[Plain English translation: we already know that life exists in our universe – VJT.]
Premise 2+: If L belongs to our background knowledge B, then Pr(R|D & B) > Pr(R|C & B).
[Plain English translation: if we already know that life exists, then the probability that life would require fine-tuning is higher if there’s a Designer than it would be if everything is ultimately the product of blind chance – VJT.]
Step 3, by 1+ and 2+: Pr(R|D & B) > Pr(R|C & B)
[Plain English translation: since we know that life exists in our universe, it follows that the probability that life would require fine-tuning is higher if there’s a Designer than it would be if everything is ultimately the product of blind chance – VJT.]
Conclusion, by 3 and the Likelihood Principle: Given our background knowledge, R evidentially favors D over C.
[Plain English translation: therefore the discovery of fine-tuning favors the hypothesis that there’s a Designer over the hypothesis that everything is ultimately the product of blind chance – VJT.]
In other words, the discovery of fine-tuning makes it more likely (from our perspective) that there is a God, if by “God,” we mean a purposeful and intelligent being outside the cosmos. And as scientists discover more and more fine-tuning in our scientific investigations of the cosmos, it will appear increasingly likely to us that there really is such a God.
(c) Night vision: why fine-tuning renders the existence of a Designer more likely
A standard dartboard. Image courtesy of Tijmen Stam and Wikipedia.
In his article, Fine-Tuning and the Infrared Bull’s-Eye, Roberts anticipates a possible objection to his new version of the fine-tuning argument: how do we know that the second premise is true? The second premise stipulated that if we already know that life exists, then the probability that life would require fine-tuning is higher if there’s a Designer than it would be if everything is ultimately the product of blind chance. But why should this be so? Why should the occurrence of fine-tuning render the existence of a Designer more likely?
To make this premise appear plausible, Roberts tells a little story. Imagine, he says, that you’ve received a very nice birthday present (actually, a set of infra-red goggles), which you haven’t opened yet, so you still have no idea what you’ve got for your birthday. Now imagine that you’re standing in front of a large wall, whose entire surface is painted white. From somewhere behind you, a dart is launched, and it zooms over your head and then hits a point on the wall. You briefly wonder whether the dart was thrown intentionally by someone, or whether it was just flung at the wall by chance. You realize that the evidence you’ve seen so far favors neither hypothesis: the point where the dart landed looks the same as any other point on the wall. Roberts takes up the story:
Then you open your birthday present, and you are delighted to find that it’s a pair of infrared-vision goggles. You put them on, and when you look at the wall again, you see that it bears a standard dartboard design done in infrared paint, and the center of the bull’s-eye is at precisely the point where the dart is sticking out of the wall. Now what do you think? It seems obvious that the only reasonable thing to think at this point is that you now have excellent evidence that the dart was carefully aimed. (And by someone or something that can see in the infrared part of the spectrum.) Why? We can reconstruct your reasoning as a likelihood argument: There being something special and aim-worthy about the point where the dart struck the wall is much less surprising and much more to have been suspected if the dart were thrown by a skillful aimer than if it were flung up there by some random process…
The analogy between this case and that of the fine-tuning argument is obvious. Our discovery of R corresponds to the discovery of the infrared bull’s-eye: It shows us that there was something intelligibly (even if not uniquely) aim-worthy or choiceworthy about the values of our universe’s parameters which they do not share with generic possible parameter-values. Just as the discovery of the heretofore invisible bull’s-eye ought to strike us as more likely given a skillful aimer than given a random flinger, so should the special feature of the actual parameter-values strike us as more likely given that they were set by design than given that they were set by chance.
This is an excellent illustration, which renders the second premise of Roberts’ argument highly plausible. What is it, precisely, that makes it rational to infer that the dart is thrown by an intentional agent? Roberts’ answer is: the fact that the target was choiceworthy or aim-worthy in a way that other spots on the wall were not. I won’t belabor this point, as Professor Carroll acknowledges in his video presentation that life is a choiceworthy goal for an Intelligent Designer: indeed, he even estimates the probability of life arising, given God’s existence, to be precisely 1, or 100%.
(d) There’s a good reason why a Designer would make a fine-tuned universe – and in any case, fine-tuning is more likely under a Designer
But an atheist might still feel inclined to pose the following question to Roberts: “Doesn’t it seem odd to claim that if a Designer wanted to create a universe capable of supporting life, then He would create a finely-balanced one, in which life would be annihilated if the physical parameters describing our universe were changed even a little? Why would He do that?”
Roberts contends that even if it were unlikely that a Designer would make a finely-tuned cosmos that was balanced on a knife-edge, rather than another kind of cosmos, the occurrence of fine-tuning is still more likely if the parameters describing our universe are set by a Designer than if the parameters are set by chance. To make his point, he uses another illustration, this time relating to screen-savers:
What the fine-tuning argument needs in order to work is not for it to be more likely than not that a designer would make R be true if it could; rather, it needs it to be more likely that R is true given both L and D than it is given L and C. This latter claim is perfectly compatible with its being the case that if there is a Designer, it would most likely make a world where fine tuning is not required.
It might be helpful to consider an analogy. I have an uncle who is not at all famous, is not a model, and does not work in the computer industry or know anybody who does. So if you notice that my screen saver features a picture of my uncle, you can reasonably be quite confident that I set up my own screen saver, instead of just using the one that came pre-installed on the computer. This doesn’t change if you also happen to know that my uncle and I are not particularly close, so that it is rather unlikely that I would choose a picture of him for a screen saver if I were setting it up myself. That doesn’t matter: As unlikely as it is that my uncle’s photo would be in my screen saver had I set it up myself, it is surely far more unlikely that his photo would be in my screen saver had my screen saver been the one provided by the manufacturer. (After all, I am at least related to the guy.) So when you see my uncle’s photo there, you have excellent grounds for favoring the hypothesis that I set up my own screen saver over the hypothesis that I used the one that came pre-installed – even though what you see is quite surprising, given the hypothesis thus favored.
Why a Designer would want to make a fine-tuned cosmos
I would now like to put forward my own answer to the skeptic’s question, “Why would God create a finely tuned universe?” So far, we’ve been talking about a Designer Whose goal is simply to create life. But I would argue that the creation of intelligent life is also a choiceworthy goal for a Designer – and I’m sure Dr. Carroll would agree with me here, since he acknowledges in his video that if God exists, then life should exist – and that a Being Who created intelligent life-forms might well want to leave them some sign of His presence, so that the intelligent beings which He had made could infer His existence. Now, I’m not arguing that fine-tuning is necessarily the best “calling card” that a Designer could leave – one could imagine messages emblazoned across the sky, for instance – but it is a pretty clear one. So if someone were to ask me why a Designer would want to make a fine-tuned universe, I would answer: “In order to leave a clear signal of His presence to His intelligent creatures, who are capable of knowing and loving their Creator.” It’s as simple as that.
(e) There are good reasons for believing that the vast majority of universes would be inhospitable to any form of biological life
Emeritus Professor Victor Stenger, a long-time critic of the fine-tuning argument. Image courtesy of Victor Stenger and Wikipedia.
In his video presentation, Professor Carroll suggests that life may be more resilient than we thought, and that for all we know, a large number of multiverses may contain life. However, there are good reasons for believing otherwise. I’d now like to quote from Dr. Luke Barnes’ paper, The Fine-Tuning of the Universe for Intelligent Life (Version 1, December 21, 2011)):
In reply, fine-tuning isn’t about what the parameters and laws are in a particular universe. Given some other set of laws, we ask: if a universe were chosen at random from the set of universes with those laws, what is the probability that it would support intelligent life? If that probability is suitably (and robustly) small, then we conclude that that region of possible-physics-space contributes negligibly to the total life-permitting subset. It is easy to find examples of such claims.
* A universe governed by Maxwell’s Laws “all the way down” (i.e. with no quantum regime at small scales) will not have stable atoms – electrons radiate their kinetic energy and spiral rapidly into the nucleus – and hence no chemistry (Barrow & Tipler, 1986, pg. 303). We don’t need to know what the parameters are to know that life in such a universe is plausibly impossible.
* If electrons were bosons, rather than fermions, then they would not obey the Pauli exclusion principle. There would be no chemistry.
* If gravity were repulsive rather than attractive, then matter wouldn’t clump into complex structures. Remember: your density, thank gravity, is 10^30 times greater than the average density of the universe.
* If the strong force were a long rather than short-range force, then there would be no atoms. Any structures that formed would be uniform, spherical, undifferentiated lumps, of arbitrary size and incapable of complexity.
* If, in electromagnetism, like charges attracted and opposites repelled, then there would be no atoms. As above, we would just have undifferentiated lumps of matter.
* The electromagnetic force allows matter to cool into galaxies, stars, and planets. Without such interactions, all matter would be like dark matter, which can only form into large, diffuse, roughly spherical haloes of matter whose only internal structure consists of smaller, diffuse, roughly spherical subhaloes. (p. 18)
… [F]ine-tuning relies on a number of independent life-permitting criteria. Fail any of these criteria, and life becomes dramatically less likely, if not impossible. (p. 20)
The physicist Dr. Victor Stenger (pictured above), a long-standing critic of fine-tuning arguments, asserts that random selections of the constants of physics generally produce viable, life-permitting stars, and suggests that life in other universes might not be so rare after all. In a tightly reasoned essay entitled, The Teleological Argument: An Exploration of the Fine-Tuning of the Universe (in The Blackwell Companion to Natural Theology, edited by William Lane Craig and J. P. Moreland, 2009, Blackwell Publishing Ltd.), Dr. Robin Collins exposes the flaws in Stenger’s claim:
The first criticism of his approach is that he does not address the question of whether these universes would have other life-inhibiting features relative to ours. For example, if one decreases the strength of the strong nuclear force by more than 50 percent (while keeping the electromagnetic force constant), carbon becomes unstable, and with a slightly greater decrease, no atoms with atomic number greater than hydrogen can exist (Barrow & Tipler 1986, pp. 326–7). This would make it virtually impossible for complex life forms to evolve. That Stenger ignores these other life-inhibiting features is clear from his equation for the lifetime of a star (which is unaffected by changes in the strong nuclear force, since none of the parameters he uses depends on this strength)…
Second, he equation he uses is based on a simple star model of stellar evolution. The equation does not take into account the complexities of a stellar evolution, such as whether the energy transport from the center of the star to the surface is by convection or radiative diffusion. More importantly, it assumes that the star is made mostly of hydrogen, which would not be the case if the strong force were increased beyond a small amount (see Collins 2003, p. 192 and references therein); further, it does not take into account the effects on star stability of quantum degeneracy, which require much more sophisticated codes to take into account. No simple equation could incorporate these sorts of complexities. As I have shown elsewhere (Collins 2003, pp. 192–3), using a simple star model, one can increase the strength of gravity a million- or a billionfold, and still obtain stable, long-lived stars with around the same surface temperature as our Sun. When one takes into account quantum degeneracy effects, however, one can only increase the strength of gravity by around a thousandfold before significantly decreasing the lifetime of stars (Collins 2003, pp. 193–4). Presumably, if one also changed one of the other constants, one could increase the strength of gravity by more than 3,000-fold and still obtain a stable, long-lived star, since it would change when electron degeneracy kicks in. In sum, life-prohibiting effects related to stellar lifetimes and stability only come to light when one begins to consider the complexity of the physics involved in stellar evolution, something Stenger has not done. (2009, p. 223)
(f) Even if there are other universes very different from our own which are capable of supporting life, it is still a surprising fact that the universe in which we live is balanced on a knife edge
Tightrope walker Maria Spelterini crossing Niagara Falls on July 4, 1876. Our universe is balanced on a tightrope. Image courtesy of George E. Curtis and Wikipedia.
Even if we grant (for argument’s sake) that Professor Carroll may be right in his claim that a wide variety of other universes are capable of supporting life, it is still a very surprising fact about our own universe that if its parameters were altered slightly, it would become incapable of supporting life. This is the central fact on which the fine-tuning argument is based.
In other words, Carroll appears to be under the mistaken impression that the fine-tuning argument stands or falls on the global claim that life-friendly universes are extremely rare, within the set of all possible universes, when in fact, the fine-tuning argument actually rests upon the more modest local claim that very few, if any, universes whose parameters are in the vicinity of those in our own universe, are capable of supporting life. In other words, our universe sticks out like a sore thumb, within the neighborhood of other universes like it. This striking fact is all that is needed to make the fine-tuning argument work.
Dr. Luke Barnes provides an excellent illustration of this point in his paper, The Fine-Tuning of the Universe for Intelligent Life (Version 1, December 21, 2011)), in his discussion of the masses of the up and down quark (see the top right graph in Figure 2, on page 22 of his paper):
Barr & Khan (2007) explored the parameter space of a model in which up-type and down-type fermions acquire mass from different Higgs doublets. As a first step, they vary the masses of the up and down quarks. The natural scale for these masses ranges over 60 orders of magnitude and is illustrated in Figure 2 (top left). The upper limit is provided by the Planck scale; the lower limit from dynamical breaking of chiral symmetry by QCD; see Barr & Khan (2007) for a justification of these values. Figure 2 (top right) zooms in on a region of parameter space, showing boundaries of 9 independent life-permitting criteria:
1. Above the blue line, there is only one stable element, which consists of a single particle Delta-double plus. This element has the chemistry of helium – an inert, monatomic gas (above 4K) with no known stable chemical compounds.
2. Above this red line, the deuteron is strongly unstable, decaying via the strong force. The first step in stellar nucleosynthesis in hydrogen burning stars would fail.
3. Above the green curve, neutrons in nuclei decay, so that hydrogen is the only stable element.
4. Below this red curve, the diproton is stable. Two protons can fuse to helium-2 via a very fast electromagnetic reaction, rather than the much slower, weak nuclear pp-chain.
5. Above this red line, the production of deuterium in stars absorbs energy rather than releasing it. Also, the deuterium is unstable to weak decay.
6. Below this red line, a proton in a nucleus can capture an orbiting electron and become a neutron. Thus, atoms are unstable.
7. Below the orange curve, isolated protons are unstable, leaving no hydrogen left over from the early universe to power long-lived stars and play a crucial role in organic chemistry.
8. Below this green curve, protons in nuclei decay, so that any atoms that formed would disintegrate into a cloud of neutrons.
9. Below this blue line, the only stable element consists of a single particle Delta-minus, which can combine with a positron to produce an element with the chemistry of hydrogen. A handful of chemical reactions are possible, with their most complex product being (an analogue of) H2 [hydrogen gas – VJT].
We may fairly conclude, then, that the popular description of the universe being balanced on a knife-edge is quite accurate.
(g) The multiverse itself requires an explanation
Every disk is a bubble universe. Universe 1 to Universe 6 are different bubbles, with distinct physical constants that are different from our universe. Our universe is just one of the bubbles. Image courtesy of Krzysztof Mizera and Wikipedia.
In an influential essay entitled, The Teleological Argument: An Exploration of the Fine-Tuning of the Universe (in The Blackwell Companion to Natural Theology, edited by William Lane Craig and J. P. Moreland, 2009, Blackwell Publishing Ltd.), Dr. Robin Collins argues that a “multiverse-generator” doesn’t eliminate the need for fine-tuning.
…[A]s a test case, consider the inflationary type multiverse generator. In order for it to explain the fine-tuning of the constants, it must hypothesize one or more “mechanisms” for laws that will do the following [four] things: (i) cause the expansion of a small region of space into a very large region; (ii) generate the very large amount of mass-energy needed for that region to contain matter instead of merely empty space; (iii) convert the mass-energy of inflated space to the sort of mass-energy we find in our universe; and (iv) cause sufficient variations among the constants of physics to explain their fine-tuning.
[T]o achieve (i)–(ii), we effectively have a sort of “conspiracy” between at least two different factors: the inflaton field that gives empty space a positive energy density, and Einstein’s equation… of General Relativity, which dictates that space expand at an enormous rate in the presence of a large near-homogenous positive energy density… Without either factor, there would neither be regions of space that inflate nor would those regions have the mass-energy necessary for a universe to exist. If, for example, the universe obeyed Newton’s theory of gravity instead of Einstein’s, the vacuum energy of the inflaton field would at best simply create a gravitational attraction causing space to contract, not to expand.
The conversion of the energy of the inflaton field to the normal mass-energy of our universe (condition (iii)) is achieved by Einstein’s equivalence of mass and energy, E = mc^2, along with the assumption that there is a coupling between the inflaton field and the matter fields. Finally, the variation in the constants (and to some extent the laws) of nature is typically claimed to be achieved by combining inflationary cosmology with superstring/M-Theory, which purportedly allows for an enormous number (greater than 10^500) possible combinations of values for the constants of physics. The important point here is that the laws underlying the inflationary scenario must be just right in order to cause these variations in the constants of physics from one universe to another. If the underlying laws are those given by superstring/M-Theory, arguably there is enough variation; this is not the case, however, for the typical grand unified theories that have been recently studied…
In addition to the four factors listed, the fundamental physical laws underlying a multiverse generator – whether of the inflationary type or some other – must be just right in order for it to produce life-permitting universes, instead of merely dead universes. Specifically, these fundamental laws must be such as to allow the conversion of the mass-energy into material forms that allow for the sort of stable complexity needed for complex intelligent life. For example, … without the Principle of Quantization, all electrons would be sucked into the atomic nuclei, and, hence atoms would be impossible; without the Pauli Exclusion Principle, electrons would occupy the lowest atomic orbit, and hence complex and varied atoms would be impossible; without a universally attractive force between all masses, such as gravity, matter would not be able to form sufficiently large material bodies (such as planets) for life to develop or for long-lived stable energy sources such as stars to exist.
Although some of the laws of physics can vary from universe to universe in superstring/M-Theory, these fundamental laws and principles underlie superstring/M-Theory and therefore cannot be explained as a multiverse selection effect. Further, since the variation among universes would consist of variation of the masses and types of particles, and the form of the forces between them, complex structures would almost certainly be atomlike and stable energy sources would almost certainly require aggregates of matter. Thus, the said fundamental laws seem necessary for there to be life in any of the many universes generated in this scenario, not merely in a universe with our specific types of particles and forces.
In sum, even if an inflationary-superstring multiverse generator exists, it must have just the right combination of laws and fields for the production of life-permitting universes: if one of the components were missing or different, such as Einstein’s equation or the Pauli Exclusion Principle, it is unlikely that any life-permitting universes could be produced. Consequently, at most, this highly speculative scenario would explain the fine-tuning of the constants of physics, but at the cost of postulating additional fine-tuning of the laws of nature.
(h) The multiverse cannot explain the beauty of the laws of physics
Rayonnant north rose window of the Cathédrale Notre-Dame de Paris. Image courtesy of Krzysztof Mizera and Wikipedia.
Several years ago, Dr. Robin Collins, a leading advocate of the fine-tuning argument, gave an excellent argument explaining why the multiverse hypothesis is unable to account for the beauty of the laws of nature in section 6 of a lecture he gave at Stanford University entitled, Universe or Multiverse? A Theistic Perspective. Collins maintained that neither the totally unrestricted multiverse hypothesized by Dr. Tegmark nor a more restricted multiverse which generates universes with different constants of nature was able to account for the beauty of the cosmos.
First of all, Collins said, we need to define what we mean by “beauty” when talking about the laws of nature. Some people would regard beauty as a wholly subjective property. However, it turns out that beauty can be given a clear and non-arbitrary definition. In his argument, Collins used the definition proposed by the 18th century English painter William Hogarth:
[T]he idea that the laws of nature are beautiful and elegant is a commonplace in physics, with entire books devoted to the topic. Indeed, Steven Weinberg – who is no friend of theism – devotes an entire chapter of his book Dreams of a Final Theory to beauty as a guiding principle in physics. To develop our argument, however, we need first to address what is meant by beauty. As Weinberg notes, the sort of beauty exemplified by physics is that akin to classical Greek architecture. The highpoint of the definition of this classical conception of beauty could be thought of as that of William Hogarth in his 1753 classic The Analysis of Beauty. According to Hogarth, simplicity with variety is the defining feature of beauty or elegance, as illustrated by a line drawn around a cone. Hogarth claimed that simplicity apart from variety, as illustrated by a straight line, is boring, not elegant or beautiful….
The laws of nature seem to manifest just this sort of simplicity with variety: we inhabit a world that could be characterized as a world of fundamental simplicity that gives rise to the enormous complexity needed for intelligent life…
For example, although the observable phenomena have an incredible variety and much seeming chaos, they can be organized via a relatively few simple laws governing postulated unobservable processes and entities. What is more amazing, however, is that these simple laws can in turn be organized under a few higher-level principles … and form part of a simple and elegant mathematical framework…
The beauty of the cosmos suggests a fine-tuning argument. The key intuition here is that even if we put aside those possible universes that cannot support life and limit ourselves to those that can support life, the vast majority of these universes will have laws that are far less beautiful than our own. As Collins put it:
One way of thinking about the way in which the laws fall under these higher-level principles is as a sort of fine-tuning. If one imagines a space of all possible laws,… the vast majority of variations of these laws end up causing a violation of one of these higher-level principles… Further, for those who are aware of the relevant physics, it is easy to see that in the vast majority of such cases, such variations do not result in new, equally simple higher-level principles being satisfied. It follows, therefore, that these variations almost universally lead to a less elegant and simple set of higher-level physical principles being met. Thus, in terms of the simplicity and elegance of the higher-level principles that are satisfied, the laws of nature we have appear to be a tiny island surrounded by a vast sea of possible law structures that would produce a far less elegant and simple physics…
Collins argues that only theism offers a ready explanation of the underlying beauty of the laws of nature. For atheism, this beauty is a surprising and wholly mysterious fact, and as Collins argues, no version of the multiverse is able to render this beauty unsurprising:
Further, this “fine-tuning” for simplicity and elegance cannot be explained either by the universe-generator multiverse hypothesis or the metaphysical multiverse hypothesis, since there is no reason to think that intelligent life could only arise in a universe with simple, elegant underlying physical principles. Certainly a somewhat orderly macroscopic world is necessary for intelligent life, but there is no reason to think this requires a simple and elegant underlying set of physical principles.
One way of putting the argument is in terms of the “surprise principle” we invoked in the argument for the fine-tuning of the constants of intelligent life. Specifically, as applied to this case, one could argue that the fact that the phenomena and laws of physics are fine-tuned for simplicity with variety is highly surprising under the non-design hypothesis, but not highly surprising under theism. Thus, the existence of such fine-tuned laws provides significant evidence for theism over the non-design hypothesis. Another way one could explicate this argument is as follows. Atheism seems to offer no explanation for the apparent fine-tuning of the laws of nature for beauty and elegance (or simplicity with variety). Theism, on the other hand, seems to offer such a natural explanation: for example, given the classical theistic conception of God as the greatest possible being, and hence a being with a perfect aesthetic sensibility, it is not surprising that such a God would create a world of great subtlety and beauty at the fundamental level. Given the rule of inference that, everything else being equal, a natural non-ad hoc explanation of a phenomenon x is always better than no explanation at all, it follows that everything else being equal, we should prefer the theistic explanation to the claim that the elegance and beauty of the laws of nature is just a brute fact.
Multiverse advocates have failed to address the beauty of the laws of nature. In the meantime, theists certainly have nothing to fear from any future scientific discovery showing that our cosmos may be embedded within some larger structure. The beauty of the laws of nature offers eloquent testimony to the existence of a Designer of nature.
In section (a), I attempted to rebut Dr. Carroll’s contention that the transcendence of God renders His existence far less likely than that of the multiverse. I also pointed out that in any case, we can calculate a minimum likelihood of 1 in 10^120 for the existence of God, and that even this very low likelihood is enough, when combined with the extremely high degree of fine-tuning in the cosmos, for us to be able to demonstrate that the probability of God’s existence, given the fine-tuning we observe, far exceeds the probability of the multiverse. Next, I contended in part (b) that Dr. Carroll had mis-stated the relevant evidence for the existence of God, which is not the existence of life (as is commonly thought), but the existence of fine-tuning. In sections (c) and (d), I then argued that the existence of fine-tuning in the cosmos renders the existence of a Transcendent Designer (God) more likely, but that it does not render the existence of a multiverse any more likely. In section (e), I rebutted the argument, put forward by Professor Victor Stenger, that a large number of multiverses may contain life, and in section (f), I maintained that even if this were the case, it would still be true that the universe in which we live is balanced on a knife edge, relative to other universes in its neighborhood – a striking fact which can be readily explained by postulating the existence of a God Who wants to make His existence known to us, but which cannot be explained by the multiverse hypothesis. In section (g), I argued that even if there were a multiverse, it would itself be fine-tuned: in other words, postulating a multiverse fails to do away with the need for God. Finally, in section (h), I explained why the beauty of the cosmos is a striking fact that points to its having had a Transcendent Creator.
In the next section, I’d like to consider one more challenge which Dr. Collins puts forward against the fine-tuning argument: his claim that the very low (but non-zero) entropy of the early universe renders the existence of God vanishingly unlikely.
How God’s Desire to be Known Explains the Puzzle of the Early Universe’s Low Entropy
Constellation Fornax, EXtreme Deep Field view. Each light speck is a galaxy. Some of these galaxies are as old as 13.2 billion years. The low entropy of the early universe is a deeply puzzling fact for modern cosmologists. Image courtesy of NASA and Wikipedia.
Later on in his video, Is God a Good Theory?, Professor Carroll addresses the question: what’s the posterior probability of God’s existence, given the data we observe? Until this point in the video, Carroll has been focusing on what he regards as the most salient piece of data about the cosmos: the fact that it contains life. Carroll generously declares that he is quite willing to grant that if God exists, then life should exist. No problems there. But it’s the other data about the universe, claims Carroll, that gets God into trouble.
Before I address this “other data,” I’d just like to note again that Professor Carroll has mis-stated the fine-tuning argument. The central piece of data that’s relevant for the purposes of the fine-tuning argument is not the existence of life, but the fine-tuning of the cosmos, which I discussed in the previous section.
The data that God can’t explain, but the multiverse might: why is the entropy of the early universe extremely low, but not zero?
So what’s the magic piece of data that totally discredits the God hypothesis, for Professor Carroll? In a nutshell, it’s the low entropy of the early universe. The term “entropy,” for the benefit of readers who don’t have a scientific background, roughly means “disorder”: the entropy of a system is a measure of how messy it is. More precisely, a system’s entropy represents the number of different possible states that the system can be in: the more states a system can occupy, the less ordered it is. Thus a system which is low in entropy is highly ordered. Now, the universe as a whole can be thought of as a system. And one of the surprising discoveries of modern physics is the fact that the early universe was very well-ordered indeed.
Physicists can calculate the value that the entropy of the early universe should have, in order for our universe to support life, and then compare it with the value that it actually had back then. Professor Carroll out that the entropy of the early universe is much, much smaller smaller than it needed to be, to allow for the existence of life. In fact, it’s lower than its natural value by a factor of 10^10^120.. To grasp what Carroll is saying here, try to imagine the number 1, divided by a very large number: 1 followed by 1 trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion zeroes. That’s a very tiny fraction indeed. The entropy of the early universe is that fraction of the value predicted by physicists. It’s been called the worst prediction in the history of physics.
Here’s how Carroll summarizes the problem in an article entitled, Does the universe need God? (in The Blackwell Companion to Science and Christianity, ed. James B. Stump and Alan G. Padgett, Wiley-Blackwell, 2012):
Roughly speaking, the large number of particles in the universe were arranged in an extraordinarily smooth configuration, which is highly unstable and unlikely given the enormous gravitational forces acting on such densely-packed matter. While vacuum energy is tuned to one part in 10^120, the entropy of the early universe is tuned to one part in ten to the power of 10^120, a preposterous number. The entropy didn’t need to be nearly that low in order for life to come into existence. One way of thinking about this is to note that we certainly don’t need a hundred billion other galaxies in the universe in order for life to arise here on Earth; our single galaxy would have been fine, or for that matter a single solar system.
That doesn’t mean that we can’t possibly explain the low entropy of our early universe by invoking the multiverse; it just means that the explanation must rely on detailed dynamical properties of the multiverse, rather than simply the requirement that life can exist…
If anything, the much-more-than-anthropic tuning that characterizes the entropy of the universe is a bigger problem for the God hypothesis than for the multiverse. If the point of arranging the universe was to set the stage for the eventual evolution of intelligent life, why all the grandiose excess represented by the needlessly low entropy at early times and the universe’s hundred billion galaxies? … It’s unclear why God would do so much more fine-tuning of the state of the universe than seems to have been necessary.
Professor Carroll elaborates on this argument in his video presentation in January 2013, in which he asserts that God, if He existed, could make a solar system capable of supporting life, without having an ordered Milky Way galaxy. And even if one wanted to argue that it would be aesthetically pleasing if the galaxy in which the solar system is located were highly organized, we still need to confront the question: why are all the other 100-billion-odd galaxies in the universe so highly ordered? There’s absolutely no need for them to be. So if we claim that God’s interest in creating a life-friendly universe is the reason for the low entropy of the early cosmos, then we have to explain the awkward fact that this entropy could have been much, much higher, and the universe could still support life. (In other words, even if the universe were a lot messier, it could still support life-forms like ourselves.) When we consider the range of possible values for the early universe’s entropy, the probability that the universe should have had such a staggeringly low level of entropy, supposing it to have been created by a God Who wanted to create life, is vanishingly low: 1 in 10^10^120. Putting it another way: it’s extremely unlikely that a God Who wanted to make a life-friendly cosmos would have made one like ours. Thus according to Carroll, the cosmos, as it stands, is evidence against the existence of God, not for it.
Perhaps a believer might argue that God is extremely fastidious, and that He likes order: He wouldn’t want to create a messy universe. Rather, He’d want to make one with all the galaxies highly ordered. That’s fine, but the problem is that the entropy of the early universe is not quite zero. If it were zero, the universe would be even more ordered than it is now. So if God were trying to make a perfectly ordered universe, then why didn’t He just set the entropy of the early universe to exactly zero? This is a point made by physicist Professor Lawrence Krauss in a recent debate (August 30, 2013) with the Christian apologist and theologian, Professor William Lane Craig.
Thus the extraordinarily low value for the entropy of the early universe poses a double conundrum for believers in God: on the one hand, it’s not quite zero, as we might expect it to be if God were an exceptionally neat Creator, but on the other hand, it’s much, much lower than it needs to be, for the universe to support life. What possible reason could God have for setting the entropy of the early universe to such an arbitrarily low (but non-zero) value?
Carroll anticipates one possible response to his argument that the low entropy of the early universe renders the likelihood of God’s existence astronomically low: maybe there’s a physical mechanism that makes the universe look highly ordered during its early history, and that’s what God used, because the laws of physics demand it. But, asks Carroll, what use is God in an explanation of this sort? The laws of physics are doing all the work, and an the invocation of God is redundant, so we may as well drop him. (Carroll is applying Occam’s razor here: avoid multiplying entities beyond necessity.)
Professor Carroll then argues that however poorly the multiverse – which is the leading rival explanation to God – accounts for the low entropy of the early cosmos, the physicists who champion this hypothesis are at least trying to explain why the figure is so astonishingly low. Multiverse theorists are making a genuine attempt to explain the extraordinarily low entropy of the early cosmos. By contrast, theologians don’t even try to explain why God would want a universe with such low entropy in the beginning: their God-hypothesis is useless.
Carroll therefore suggests that we ditch the God hypothesis in favor of the multiverse.
The God Who wants to be known: what Carroll’s argument overlooks
The fatal assumption underlying Professor Carroll’s argument against theism is that God simply wants to create life (perhaps also, intelligent life), and nothing more. But if God is a Personal Being, then it is reasonable to infer that He would want to have a relationship with us. It is also reasonable to infer that if He wanted to have a relationship with us, He would leave a fairly clear sign of His Existence. I would argue that the low entropy of the cosmos is just such a sign, and I would suggest that there is a special reason why it has the low, non-zero value it has.
How a theistic physicist might explain the low entropy of the early universe
Religious believers hold that the universe is the creation of a free and intelligent Supernatural Being, Whom they call God. However, liberty of choice and liberty of spontaneity are two very different things. There is an important distinction between a free decision by an intelligent agent and a purely arbitrary or random decision: the former requires a justifying reason of some sort, while the latter does not. Consequently, if the laws, parameters and initial conditions of the universe were the result of a free decision on God’s part, we would expect to find something non-arbitrary about the extraordinarily value of the entropy of the early universe. They had to have been set that way for a reason.
The first suggestion I would like to make is that even though that we don’t need a hundred billion other galaxies in the universe in order for life to arise on Earth, we would still expect a Creator of the universe to make a universe that looked elegant to human observers, if He were leaving a sign of His presence. An unexpectedly well-ordered universe would, after all, be a better signal of God’s presence than one which had no more order than was necessary to produce life: the latter universe might easily be mistaken for one of the lucky universes in the multiverse that just happened to be capable of supporting life, whereas the former universe (which contains much more order than is necessary) would not. Thus human observers should expect to find well-ordered galaxies in every nook and cranny of the cosmos.
My second suggestion is that the value of the early universe’s entropy may be a threshold value: if it were even slightly higher, the universe would look noticeably less orderly to human observers than it does now. Perhaps there would be a few corners of the universe that were totally chaotic. Or perhaps matter, on some microscopic scale, would be noticeably less orderly in its behavior than the matter we observe. In other words, the universe would look inelegant or messy to human observers – especially scientists. Because God wanted to make a universe which is science-friendly as well as life-friendly, He made the universe with a very low initial entropy. On the other hand, I would predict that making the entropy even lower wouldn’t make any appreciable observational difference, from the point of view of scientists doing their research. In other words, the universe has the low initial entropy it has, because God intended it to be just ordered enough to be science-friendly – and no more. Making it that way and giving it a very slight non-zero initial entropy would actually be a clearer signal of God’s presence than giving it a zero initial entropy.
My third suggestion is that the entropy of the early universe was set with a view to the emergence of intelligent beings at a certain time in the universe’s history. The emergence of intelligent life-forms could not have occurred until sufficiently metal-rich stars (Population I stars) had formed, several billion years after the Big Bang. What I’m proposing is that God designed the universe in such a way that at the time when the first intelligent life-forms emerged, the universe was still (just) ordered enough for it to be investigated at all scales and in every corner of the sky, and still appear well-ordered. If intelligent life-forms had appeared at a much later time in cosmic evolution than they did, then the entropy of the early universe would have had to have been even lower than it actually was.
It should be borne in mind that the foregoing suggestions may well be completely wrong – after all, I’m not a scientist. What I intended to show by making these proposals is that the “God hypothesis” is not a science-stopper, despite frequent claims to the contrary. At the present time, it is reasonable to think that the very low but non-zero entropy of the early universe may be a sign pointing to the existence of a Creator of the cosmos, and that there may be a special reason why it has the value it has. In any case, the evidence marshaled in the previous section should put this conclusion beyond reasonable doubt.
There has been much talk in scientific circles recently about a 2013 paper by Anna Ijjas, Paul J. Steinhardt and Abraham Loeb, titled, Inflationary paradigm in trouble after Planck2013. The authors of the paper question the cosmological theory of inflation, which postulates that the universe underwent a period of extremely rapid expansion shortly after the big bang, and that it has been expanding at a slower rate ever since. What I think their paper does instead is lend powerful support to the fine-tuning argument, which claims that the physical constants, initial conditions and laws of the universe were designed by God. In my recent post, New cosmology paper by skeptical scientists lends support to the fine-tuning argument (October 30, 2013), I argue that this conclusion follows naturally if we assume that the Intelligent Designer of the cosmos wanted to not only make a universe that is hospitable to intelligent beings like ourselves, but also to send a clear signal of His existence to these intelligent beings.
I conclude, then, that the existence of God is by far the best explanation of the fine-tuning of the cosmos.