How does fine-tuning provide evidence for God?

In my previous blog, I defined the following fine-tuning claim:

“In the set of possible physical laws, parameters and initial conditions, the subset that permits rational conscious life is very small.”

I pointed out how this fine-tuning claim is widely accepted within the physics community and that some skeptics even admit that it’s not unreasonable to view this as evidence for cosmic design if there are not a multitude of other universes with different randomly-set constants. In this blog I’ll make a philosophical case that the fine-tuning of the universe for life constitutes evidence for God.

Let’s apply a methodology commonly used in science for making an inference to the best explanation.1 Scientists frequently evaluate candidate models based on how well predictions of those models match observations. In an atheistic origins model, the constants governing the laws of physics and the initial conditions were either set randomly or at least without respect to their consequences for bringing about intelligent life. In a theistic model, however, it’s not surprising to think that God would prefer a universe which supports rational conscious creatures. The skeptic who raises the problem of evil as an objection to God’s existence is implicitly affirming this expectation that God should favor conscious life. 2

Another expectation of skeptics also supports the inference from fine-tuning to divine design – the claim that God should leave some evidence for his existence. It is unsurprising that God would want to create a universe in which it appears that initial conditions and laws were set up providentially to reveal a purpose for the universe. If nearly any set of constants would have resulted in intelligent life, then it would appear as though no intervention was required to setup life-supporting physics. Conversely under atheism, there is no reason to expect that a life-supporting universe would be unlikely among possibilities. Indeed many skeptical scientists who have studied this fine-tuning data admit its surprising nature under their worldview. David Deutsch, for example, writes: “If anyone claims not to be surprised by the special features that the universe has, he is hiding his head in the sand. These special features are surprising and unlikely.”

Fine-tuning, if true, therefore, favors the hypothesis of theism over atheism because this data is much more likely on theism than atheism. This falls out from the likelihood principle from Bayesian probability theory. We can examine fine-tuning in isolation to see how one should adjust the credence for inferring God’s existence. My claim is simply that whatever was one’s prior epistemic probability for God’s existence, this fine-tuning evidence should make the hypothesis that God exists epistemically more likely than previously thought. So I’m not claiming proof of God’s existence but rather that fine-tuning is evidence for God’s existence.

Even many agnostics or atheists seem to agree that at least prima facie the fine-tuning looks like divine design. The fine-tuning is one of the key lines of evidence that led philosopher Antony Flew to renounce his long-held atheism. Here are a few quotes capturing the reaction among prominent skeptics that have studied this evidence:

“The impression of design is overwhelming. 3” Physicist Paul Davies

“A common sense interpretation of the facts suggests that a superintellect has monkeyed with physics … and that there are no blind forces in nature.4” Physicist Fred Hoyle

“As we survey all the evidence, the thought insistently arises that some supernatural agency – or, rather, Agency – must be involved. Is it possible that suddenly, without intending to, we have stumbled upon scientific proof of the existence of a Supreme Being? Was it God who stepped in and so providentially crafted the cosmos for our benefit?5” Astronomer George Greenstein

“Luck in the precise form and nature of fundamental physical law is a different kind of luck from the luck we find in environmental factors. It cannot be so easily explained, and has far deeper physical and philosophical implications. Our universe and its laws appear to have a design that both is tailor-made to support us and, if we are to exist, leaves little room for alteration.6” Stephen Hawking. He also says that the fine-tuning may reveal “a divine purpose in Creation and the choice of the laws of science.” To be clear, Hawking ultimately rejects this interpretation but admits the facts seem to support this viewpoint if there were no multiverse.

“If there is an inexplicable coincidence in the fundamental constants of nature whose values have to be precisely-tuned within a wide range of otherwise available possibilities that would make a complex universe possible then this constitutes a phenomenon that very naturally invites explanation in terms of a cosmic scale designer.” Oxford Philosopher Peter Millican  in his debate with William Lane Craig. Millican rejects the conclusion of design but seems to agree with my argument thus far that if the universe is fine-tuned it should serve as evidence for God.

The Philosophical Basis of a Fine-Tuning Argument for God

My philosophical argument is based on philosopher of science John T. Roberts’ formulation. The existence of life is treated as “background knowledge while the fact that fine-tuning is required for life serves as the evidence.” Roberts has an excellent illustration to elucidate the argument. Suppose that you witness a dart coming from behind you and landing on an enormously large wall that is homogeneously white. You wonder whether the dart was skillfully aimed or just flung in a random direction. You might be tempted to think that the dart was aimed since it’s incredibly improbable to have landed at that particular point on this enormous wall but that would be mistaken. There is nothing to distinguish the dart’s landing spot from any other location. Suppose that you then put on a pair of infrared goggles and see that there is actually a single, tiny bull’s-eye surrounding the dart on the wall. Now an inference that the dart was aimed seems plausible.

One can easily see how this analogy applies to the fine-tuning. Whether or not the dart was aimed is analogous to the question of whether or not there was intent in the setup of physics. No one argued for design based on the particular constants of physics until knowledge was gained that there was something special about those constants – life-permitting values were enormously rare. There was no significance at all in recognizing that constants permitted life – the perception of specialness arose when the set of life-permitting values were discovered to be a miniscule subset among possibilities. A universe containing life would be an aim-worthy target for a Creator. Most fine-tuning advocates run an argument for theism based on God favoring a life-permitting Universe but Roberts’ way of framing the argument side-steps certain objections as will be seen in future blogs.

Some readers may not be seeing the full force of the argument because I haven’t yet presented the extensive evidence that the universe is finely-tuned. Consider that many different parameters must each be finely-tuned – so it’s really like having many darts each hit a bull’s-eye. The inference to design will be more easily recognized if we shed some light as to the specialness of the required values. Consider the size of the bull’s eye and wall based on just 1 parameter – the cosmological constant. There is a natural range for possible values for this constant because there are known contributions that are 10120 times larger than the overall net value. (There is a near perfect but inexact cancellation of contributions accurate to 120 decimal places). Let’s use the most conservative numbers in the physics literature that indicate a fine-tuning to 1 part in 1053. If the cosmological constant, which governs the expansion rate of the universe, had been larger than its current value by this tiny fraction, then the universe would have expanded so fast that no stars or planets would have formed and therefore no life. If the value were smaller by this amount then the universe would have rapidly collapsed before the universe cooled sufficiently to allow for stable information storage which is required by any self-replicating system such as life. (And could intelligent life really emerge if the universe lasted only a few days even under ideal conditions?) Using this ratio, the size of the wall containing a single inner bull’s-eye of the size on a standard dart board, would be over 376 million light years on each side. A light-year is the distance light travels in a year – at 186,282 miles per second this is pretty far. The inference that the dart was aimed to the special area where life is possible seems reasonable – and that is just considering one of the finely-tuned parameters!

For one who assumes that nature is all there is, it is very surprising that the universe began in such an improbable state that it could support life and that a number of fundamental parameters whose values are not dictated by any known underlying theory all happen to lie in a narrow life-permitting region. This should cause one to question the assumptions of the naturalistic worldview.

1To clarify, I’m not making a scientific argument but rather a philosophical argument which relies on scientific data to affirm the truth of the premise that life-permitting universes are rare among possibilities.
2Refer to writings by Alvin Plantiga and William Lane Craig and others on the problem of evil as it’s tangential to my fine-tuning argument.
3Davies, The Cosmic Code, p. 203.
4Fred Hoyle, “The Universe: Past and Present Reflections.” Engineering and Science, Nov 1981. pp. 8–12
5Greenstein, George. The Symbiotic Universe, p.27.
6Hawking, Stephen. Grand Design, p. 162.


Picture (courtesy of Richard Matthews)

If you don’t want God, you better have a multiverse!

Such is the advice from Bernard Carr in grappling with the fascinating discovery that the physics of the universe had to be fine-tuned if it were to support life. Carr views the only viable options as being either God or a multiverse (the theory that there are a vast number of other universes). Stanford physicist Leonard Susskind also calls our attention to these relatively recent discoveries: “Science may be undergoing a huge course correction, a paradigm shift. A titanic controversy has erupted over the strange anthropic pattern that nature seems to exhibit – the pattern of extraordinary unexplained coincidences that are necessary for our own existence.[1]” I will discuss these fine-tuning discoveries and their implications in a series of blogs as part of my ongoing series on scientific evidence for God.

Here are my previous blogs in this series prior to the recent hiatus:


Can Science Disprove God?
What Counts as Evidence for God from Science?

Evidence for God from the Origin of the Universe:

Origin of the Universe

Doesn’t Quantum Mechanics Violate the Causal Principle?

Much Ado About Nothing

Philosophical Arguments that the Universe had a Beginning

 Before presenting the actual fine-tuning scientific data, I want to explore the philosophical basis of the argument. We can then examine the scientific data relative to some reasonable evaluation criteria.

What is Fine-Tuning?

Fine-tuning is not a synonym for design but is rather a technical term in physics that refers to a narrow range for suitable values among possibilities. All else being equal, if theory A requires fine-tuning and theory B doesn’t, then theory B is deemed to be more likely to be true because it doesn’t rely on assumptions for narrow constraints for the values of one or more parameters. There are other contexts where fine-tuning is discussed with respect to various hypotheses having nothing to do with life, but I defend this fine-tuning claim:

“In the set of possible physical laws, parameters and initial conditions, the subset that permits rational conscious life is very small.”

The universe is said to be finely-tuned for life if most possible ways for setting up physics would have resulted in no intelligent life anywhere in the universe. My claim is close to that defined by Luke Barnes[2] in his important review article. I use the term “rational conscious life” rather than “the evolution of intelligent life” because the fine-tuning claim can be evaluated independently of biological evolution. My wording also reflects Christian expectations that God wanted creatures in His image – rational, conscious creatures with whom He could have a relationship.

It’s important to note that my fine-tuning claim deals with the fundamental physics of the universe required before any biological evolution could get started. I personally happen to be skeptical of the all-encompassing claims about naturalistic macroevolution but even if it explains the full diversity of life that is irrelevant to my fine-tuning claim. For example, a universe without one type of fine-tuning would have lasted only a few hours and never cooled below 9000K. Thus, it is unreasonable to expect such a universe to have contained life – much less intelligent life. Physicists writing fine-tuning articles routinely make claims about life being impossible without certain finely-tuned parameters or initial conditions. Craig Hogan, for example, is very explicit, stating that “changing the quark masses even a small amount has drastic consequences [for] which no amount of Darwinian selection can compensate.” Alan Lightman of MIT clarifies the nature of the fine-tuning: “if these fundamental parameters were much different from what they are, it is not only human beings that would not exist but no life of any kind would exist.” No biological evolution can start until you have the first living cell and the vast majority of ways to setup the physics never allow life to get started.

My future blogs will detail some of the evidence supporting my fine-tuning claim but here is a foretaste from atheist physicist Stephen Hawking’s best-selling book, A Brief History of Time (on p. 125):

“The remarkable fact is that the values of these numbers [i.e. the constants of physics] seem to have been very finely adjusted to make possible the development of life. For example, if the electric charge of the electron had been only slightly different, stars would have been unable to burn hydrogen and helium, or else they would not have exploded. It seems clear that there are relatively few ranges of values for the numbers [i.e. the constants of nature] that would allow for development of any form of intelligent life.”

How widespread is the acceptance of fine-tuning among physicists?

In a word – very! In my years of researching this topic, I’m amazed at how few scientists who have studied the fine-tuning details disagree with this core claim that the subset of life-permitting physics is a tiny fraction among possibilities. Since Luke Barnes is a top researcher on this topic, consider his input on the level of acceptance of the fine-tuning claim: “I’ve published a review of the scientific literature, 200+ papers, and I can only think of a handful that oppose this conclusion, and piles and piles that support it.[3]

Of course, any topic with potentially significant philosophical or even spiritual implications is likely to encounter some opposition. Many physicists who accept the fine-tuning data do not, of course, embrace the design implicationsSome readers might be wondering how the skeptics interpret this evidence. The most common response among skeptical physicists is an appeal to the multiverse as alluded to in the introduction.



Is the multiverse a satisfying
explanation of the fine-tuning?

If we have an enormous number of other universes and if they have widely varying laws, then perhaps sufficient probabilistic resources exist for life to emerge in some universe. We need to carefully evaluate how well the multiverse serves as a potential explanation for fine-tuning. Here are some potential challenges to a multiverse explanation of the fine-tuning:

– No empirical evidence exists for any universe other than our own

– We need vast numbers of other universes to overcome horrendous odds against a life-permitting universe – probably more than 10100 (which is more than the number of subatomic particles in our observable universe)

– A universe generating mechanism might itself require fine-tuning to generate so many universes

o This is certainly true for the most popular multiverse theory – eternal inflation.

♦ Sean Carroll admits[4] that “inflation only occurs in a negligibly small fraction of cosmological histories, less than 10-66,000,000.”

o Also, other assumptions are required for eternal inflation – as Vilenkin admits: “The most likely thing to pop out of the [quantum vacuum] is a tiny Planck-sized universe, which would not tunnel, but would instantly recollapse and disappear. Tunneling to a larger size has a small probability and therefore requires a large number of trials. It appears to be consistent only with the Everett interpretation.” This Everett or many-worlds interpretation of quantum physics is one of a dozen or so interpretations and many physicists are skeptical of this interpretation because it entails that parallel universes are spawned at every quantum event.

–  The new universes would need to have different physical constants

o There are many theoretical reasons for thinking constants might vary but we have no clear evidence that fundamental constants have ever been more than trivially different in different parts of our observable universe. Without new physics in each universe, our odds for life wouldn’t be helped – it’d be like buying a million lottery tickets with the same set of numbers for each ticket!

–  The constants would need to vary extremely widely

o The degree of variety in possible values for the constants may not be sufficient unless a particular version of string theory is true. Some string theorists think that perhaps there are as many as 10500 different possible values for the constants. This variance would be more than sufficient. Polchinski, however, is one of many string theorists who disagree with this proposal – “there is no reason to expect … a large number of variations in the constants of physics.[5]”

♦ A significant minority segment of the physics community is highly skeptical of any version of String Theory because it thus far has no clear empirical confirmation and a history of failed predictions.

– It is fallacious to view the fine-tuning itself as evidence for a multiverse since the existence of other universes doesn’t make it any more likely that our universe supports life. We need independent evidence for the multiverse hypothesis before it becomes a viable candidate explanation of the fine-tuning. MIT philosopher of science Roger White shows this using Bayesian logic and summarizes: “the fact that our universe is fine-tuned gives us no further reason to suppose that there are universes other than ours.”

– Is the multiverse theory even scientific?

o Personally I’m not too concerned about this question – we just want to follow the evidence wherever it leads even if that is beyond the realm of direct empirical confirmation. It should be pointed out though that the most popular multiverse theories, such as eternal inflation, postulate other universes that could not have interacted with our universe, even in principle. About the only way to affirm such multiverse theories is to examine how well our universe conforms to multiverse predictions after applying a selection effect due to the constraint that observers can only observe a life-permitting universe. This selection effect is known as the anthropic principle although it really deals with any type of observer whereas ‘anthropic’ is derived from the Greek word ‘anthropos,’ which means human.

o Thus, our universe should be typical among life-permitting universes. If our universe appears “overly” fine-tuned it would still look more like the product of design than a random member of an ensemble of life-permitting universes. For further information about this widely accepted principle among multiverse advocates, see this excellent book of essays by prominent physicists entitled Universe or Multiverse?

♦ Many scientists are highly critical of this approach of trying to indirectly affirm the multiverse. However, some skeptical scientists seem willing to accept this approach because it seems to be the only way to avoid the design implications of the fine-tuning. Polchinski, a leading string theorist, acknowledges that “anthropic reasoning runs so much against the historic goals of theoretical physics that I resisted it long after realizing its likely necessity. But now I have come out.”[6] Susskind claims that “the stakes are to accept the [string] landscape and the dilution in the scientific method it implies or give up science altogether and accept intelligent design (ID) as the explanation for the choices of parameters of the standard model.”[7]

As we’re examining the fine-tuning evidence in future blogs, I’ll point out cases where parameters are significantly more fine-tuned than is necessary since this counts against the multiverse as a solution to the fine-tuning problem. As a preview consider that many physicists such as Lee Smolin have pointed out problems in this arena such as proton decay rates being many orders of magnitude smaller than the life permitting region. Also, Oxford physicist Roger Penrose says that the multiverse is “worse than useless” as explanation of the finely-tuned initial conditions because the multiverse predicts hyper-exponentially more tiny universes than large ones like ours.

Some physicists have rightly pointed out that a multiverse by itself is not necessarily a violation of Occam’s razor since it could arise from a simple law-like mechanism for generating universes. The key issue though is that for the multiverse to be an adequate explanation for the fine-tuning it requires the conjunction of several hypotheses for which we lack anyempirical evidence:

  1. A universe-generating mechanism that generates a plethora of universes
  2. That this mechanism doesn’t itself require fine-tuning
  3. The many-worlds interpretation of quantum physics
  4. The ability to widely vary constants in those universes. If you think that it’s a foregone conclusion that String Theory/M-Theory[8] will come to the rescue in this area, you should watch this video clip by Oxford physicist Roger Penrose where he exclaims that “it’s not even a theory … it’s a collection of hopes”.

Occam’s razor therefore does seem to favor design over the multiverse. When one accounts for the extensive problems in affirming premise 2 and how these multiverse theories make predictions incompatible with our universe, the hypothesis that God designed the physics of the universe to bring about life is more plausible. That so many physicists appeal to the multiverse to explain away the design implications of fine-tuning testifies to the power of this argument!


[1] Susskind, The Cosmic Landscape: String Theory and the Illusion of Intelligent Design. The Chattahoochee Review Podcast. (near about the 6th minute)

[2] I highly recommend Barnes’ excellent blogs correcting various people on both sides of the debate when they make mistakes in their analysis of the math, physics, or philosophy. I hope I can get more people to read his blogs. I recommend his blogs more than my own – I’m just trying to be a popularizer of the excellent scholarly work that is out there!

[3] To support the claim that Barnes is a top researcher/thinker on fine-tuning consider that he was invited to speak at last summer’s Philosophy of Cosmology conference. Here is his blog article from which I obtained his quote:

[4] Carroll, Tam. Unitary Evolution and Cosmological Fine-Tuning.

[5] Polchinski, String Theory. (1998, Vol. 2, pp. 372-73).

[6] Lee Smolin. The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next. (New York: Houghton Mifflin Co., 2006), 169.

[7] Ibid., 197.

[8] M-Theory is simply a more generalized version of String Theory


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Image: Courtesy of Kevin Hainline

Is the universe fine-tuned for life and is this evidence for God?

Sometimes people ask about fine-tuning and I created this overview to just provide links to all of my fine-tuning blogs on I’ll update this as I add to this. I defend this fine-tuning claim which is actually widely accepted in the physics community:

“In the set of possible physical laws, parameters and initial conditions, the subset that permits rational conscious life is very small.”

Of course whether that implies design is more controversial but I defend the case that it does:

Intro/Philosophical Background

If You Don’t Want God, You Better Have a Multiverse!

How Does Fine-Tuning Provide Evidence for God?


Fine-Tuning of Initial Conditions to Support Life

Many Changes to the Laws of Physics Would be Life-Prohibiting

Fine-Tuning of the Force Strengths to Permit Life

Fine-Tuning of Particles to Support Life


Mistaken Objections that Seek to Trivialize Fine-Tuning

Important Objections in the Fine-Tuning Debate

But We Can’t Even Define Life

Coarse-Tuning vs. Fine-Tuning

For a more in-depth defense of the scientific case (and some excellent philosophical points), I highly recommend Cosmologist Luke Barnes:

  • Dr. Barnes has an excellent podcast for popular audiences.
  • Here is the most comprehensive peer-reviewed review article on Fine-Tuning and an excellent rebuttal to Fine-Tuning skeptic Vic Stenger.
  • Barnes has some excellent videos on this topic as well – here is one.
  • Finally here are some excellent blogs by Barnes on this topic.