What Do Prominent Physicists and

Cosmologists Say About Fine-Tuning?

Vic Stenger

September 18, 2012


In my 2011 book The Fallacy of Fine-Tuning: Why the Universe Is Not Designed for Us, I disputed the claims that the apparent fine-tuning of the constants of physics provides convincing evidence for divine design in the universe.[1] Critics of my book have claimed that my views are totally at odds with those of the physics and cosmology communities. Here I will report on my direct communications with several prominent physicists and cosmologists, which show that, while they do not agree with me on all counts and wish to avoid getting caught up in theological disputes, it is misleading to claim their support for theistic claims.

       On September 1, 2012, I wrote to each: “In 2011 I published a book titled The Fallacy of Fine-Tuning: Why the Universe Is Not Designed for Us (Prometheus Books). If titles were allowed to be more descriptive, the main title would have been The Fallacy of the Notion that the Parameters of Cosmology and Physics Are So Fine-Tuned for Life, Especially Human Life, that They Can Only Have Been the Result of Supernatural Design.”

       In my initial emails, I asked them:

Would you be kind enough to reply on whether you agree or disagree with the following two statements that summarize the position I develop in the book:


1. The universe is not fine-tuned to us; we are fine-tuned to the universe.


2.  Based on existing knowledge, we cannot demonstrate that a natural explanation for the apparent fine-tuning is so unlikely as to provide a strong case for the existence of supernatural intelligent design in the universe.


Here are the results.


Martin Rees

Martin Rees is the Astronomer Royal of the United Kingdom and one of the most eminent astronomers and cosmologists in the world. I have communicated with Lord Rees by email several times in the past and he has always graciously responded. He did so again here and we had several exchanges.

Given his high position in the Kingdom, he understandably has to be very careful about what he says and to avoid controversy. He requested that our emails remain private, which I will certainly respect. However, I am free to quote from any published book or paper.

Lord Rees has written much on the subject of fine-tuning, both technical and popular,[2] and suggested the following reference to a paper based on a chapter from a memorial volume for Fred Hoyle, “Numerical Coincidences and 'Tuning' In Cosmology.”[3]

In this paper, Lord Rees says, “It is not guaranteed that simple equations permit complex circumstances.” That is hardly a strong endorsement of Intelligent Design. Contrary to the claims of those who promote Intelligent Design, the spontaneous, purely natural transition from simplicity to complexity, if not guaranteed, certainly happens in the natural world. Simplicity begets complexity. The prime example is how, left alone in the absence of any external heat, water changes phase from a simple vapor to less simple liquid to a complex solid.

Lord Rees rejects the claim of theists that the multiverse scenario, which makes anthropic selection a no-brainer, is untestable. He remarks, “Such a hypothesis could even be refuted: this would happen if our universe turned out to be even more specially tuned than our presence requires.” It should be clear from this quotation that he does not think that, as far as we can currently say, the universe is so finely tuned for it to require an external designer.

Nothing in the published writings of Lord Rees contradicts any of the main conclusions of my book.


Andrei Linde

Andre Linde was one of original cosmologists who independently proposed the theory of the inflationary universe.[4] I believe he was also the first to seriously propose the multiverse scenario.[5] Here is how he answered my two questions:

1. The universe is not fine-tuned to us; we are fine-tuned to the universe.

“The answer is ‘maybe.’ To explain what I mean: In the theory of inflationary multiverse, based on string theory, the laws in different parts of our universe may differ from each other. There are about 10500 different possibilities. We live in those parts of the universe where we can exist, just like dolphins cannot exist on dry land. It is crucial though that our universe is in fact a multiverse. For a brief introduction to the idea, see http://arxiv.org/pdf/hep-th/0211048.pdf and http://arxiv.org/pdf/hep-th/0302219.pdf.

“So, the universe can be easily fine-tuned for any kind of life, including ours. No design is needed. If the universe exists in a single copy (no different types of laws of physics), or if one of the available possibilities for the universe is overwhelmingly more probable than all alternatives, then it is possible that we are fine-tuned to the universe, see e.g. http://arxiv.org/pdf/1011.0119.pdf. However, this option, while possible, does not seem very likely to me. We hope to learn more about it in the future.”


2. Based on existing knowledge, we cannot demonstrate that a natural explanation for the apparent fine-tuning is so unlikely as to provide a strong case for the existence of supernatural intelligent design in the universe.

“Sure. You may look at the closely related book by Susskind on this issue:[6]



I have read Susskind’s book. In Fallacy I did not dismiss the multiverse scenario, which obviously solves the fine-tuning conundrum. I was simply trying to show that, based on well-established physics and cosmology (no speculations about strings, etc.), even for a single universe the constants of physics cannot be shown to be so tightly constrained that no natural explanation is viable.


Lee Smolin

Lee Smolin is a well-regarded theoretical physicist at the Perimeter Institute in Canada. He is the author of several excellent popular books and is noted for his original work on theories of quantum gravity that do not involve String theory. Here’s what he wrote:

“Thanks for writing. I disagree with 1 and agree with 2. My view is that the parameters of the standard models of physics and cosmology are fine tuned for the production of massive stars leading to black holes, and that this can be explained as a result of dynamical processes acting in the past, which I propose in the theory of cosmological natural selection. This explains the hospitality of the universe for life such as the plentitude of carbon and oxygen as a byproduct of the fitness of the universe without any need for theological explanations and in a way that is falsifiable.

“This was discussed at length in my first book, Life of the Cosmos and I return to it in my forthcoming book, Time Reborn. I am attaching review articles that describe the current status of cosmological natural selection.”[7]


When Smolin says he disagrees with my first question, it is clear that he is not adopting the view that the universe is fine tuned to “us” humans, but rather to life like ours based on carbon and oxygen. Furthermore, he is not confirming supernatural design. Quite the opposite, he is proposing that a natural selection process takes place in the formation of universes that favors those with ample carbon and oxygen.

       Smolin’s ideas in no way refute anything in my book.


Alan Guth

Alan Guth gained instant fame in 1981 with his proposal that the universe underwent a period of exponential inflation shortly after it appeared lasting a tiny fraction of a second before flattening out in the conventional, almost linear, big bang.[8] While others,[9] including Linde as mentioned above, independently arrived at this notion, Guth recognized its full significance in solving a number of existing problems in cosmology. Here’s how he responded:


“I certainly agree with you that the fine-tuning of the universe does not imply any form of supernatural intelligent design. I agree with your two statements,


1. The universe is not fine-tuned to us; we are fine-tuned to the universe.


2. Based on existing knowledge, we cannot demonstrate that a natural explanation for the apparent fine-tuning is so unlikely as to provide a strong case for the existence of supernatural intelligent design in the universe.


But I would expand a bit to mention that I consider the cosmological constant problem to be very real. It needs some explanation, although the intelligent design solution does not make much sense to me. I consider the cosmological constant problem much more compelling than the other instances of fine-tunings that are discussed, since the strikingly small value of the cosmological constant (compared to the Planck scale or the supersymmetry-breaking scale) is rather shocking, and does not require any assumptions about the nature of life to appreciate. I would add that I find the explanations that you mention in your chapter on the subject, other than the multiverse explanation, to be very unconvincing. None of them comes close to having a solid mathematical formulation. Thus, I consider the cosmological constant problem to be a significant piece of evidence for the multiverse.

“Concerning the need for a deity, I may differ slightly from you on one related point. (I'm not really sure what you would say about this, so maybe we agree.) I would say that we know essentially nothing about where the laws of physics came from. I would therefore say that anyone who wants to attribute the laws of physics to God is certainly welcome to do so, without any fear of contradicting anything I know about science. I might add, however, that I don't see that this hypothesis helps in any way to explain where the laws of physics come from. One can simply define ‘God’ to be the entity responsible for the laws of physics, but then one is still at a loss to learn what other properties ‘God’ might have, or what origin ‘God’ has. So, the problem of the origin of the laws of physics seems to just be pushed back one level, with no advantage.”


       First, Guth agrees with my two statements and states very clearly that fine-tuning does not imply Intelligent Design. Second, he has read my book and makes only one negative comment. He is unconvinced by my proposed possible solutions to the cosmological-constant problem. However, he does not in anyway imply that a purely natural solution to the problem is impossible.

One of the major misunderstandings of my book is on the matter of burden of proof. Several of my critics have objected that I have not proved this or that. Well, I don’t regard the burden of proof to rest on my shoulders. The one who makes the more extraordinary and less parsimonious claim, in this case that the universe is fine tuned for life by a creator God, has the burden of proving that all plausible natural explanations are impossible.

As for the laws of physics, I refer you to my 2006 book The Comprehensible Cosmos: Where Do the Laws of Physics Come From?[10] The arguments I make in Fallacy do not depend on the proposal I made in that book.

In sum, those religious apologists who attempt to discredit the Fallacy of Fine-Tuning by claiming that I am in severe disagreement with the scientific community are simply wrong. As we have seen, the prominent physicists and cosmologists I contacted do not agree with me 100 percent. So, what else is new? That’s what science is all about: doubt, dispute, devil’s advocacy.

Other scientists whose names have been mentioned by my critics include Franck Wilczek, Stephen Hawking, and Leonard Susskind. I could not reach Wilczek, did not want to bother Hawking, and have so far received no response from Susskind.

I wish scientists everywhere would speak out more forcefully against those who claim that science has uncovered convincing evidence for a creator God.



[1] Victor J. Stenger. The Fallacy of Fine-Tuning: Why the Universe is Not Designed for Us. Amherst, NY: Prometheus Books, 2011.

[2] Martin J. Rees. Just Six Numbers: The Deep Forces That Shape the Universe. New York: Basic Books, 2000.

[3] Martin Rees, “Numerical Coincidences and 'Tuning' In Cosmology, ” http://lanl.arxiv.org/pdf/astro-ph/0401424v1.pdf (accessed September 5, 2012).

[4] Andrei Linde. “The Self-Reproducing Infaltionary Universe.” Scientific American Presents, 1998, 98-104.

[5] A.D. Linde. “Eternally Existing Self-Reproducing Chaotic Inflationary Universe.” Physics Letters B 175, no. 4 (1986): 395-400; “The Self-Reproducing Infaltionary Universe.” Scientific American Presents, 1998, 98-104.

[6] Leonard Susskind. Cosmic Landscape: String Theory and the Illusion of Intelligent Design. New York: Little, Brown and Co., 2005.

[7] Lee Smolin. The Life of the Cosmos. New York: Oxford University Press, 1997; 2006. “The Status of Cosmological Natural Selection” http://arxiv.org/pdf/hep-th/0612185v1.pdf (accessed September 5, 2012); 2012. “A Perspective on the Landscape Problem.” http://arxiv.org/pdf/1202.3373v1.pdf (accessed September 5, 2012).

[8] Alan H. Guth. “Inflationary Universe: A Possible Solution to the Horizon and Flatness Problems.” Physical Review D 23, no. 2 (1981): 347-56.; The Inflationary Universe: The Quest for a New Theory of Cosmic Origins. Reading, MS: Addison-Wesley Publishing, 1997.

[9] Demos Kazanas. “Dynamics of the Universe and Spontaneous Symmetry Breaking.” Astrophysical Journal 241 (1980): L59-L63.

[10] Victor J. Stenger. The Comprehensible Cosmos: Where Do the Laws of Physics Come From? Amherst, NY: Prometheus Books, 2006.