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.


Picture (courtesy of Richard Matthews)

 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.

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3 replies
  1. John Moore says:

    Here’s another deep sciencey question: You say “many different parameters must each be finely-tuned,” but what if all the constants are inter-related? What if all the physical constants can be derived from just one absolutely fundamental constant, such as the Planck constant?

    Have you read where scientists address this question? I’d be glad if you pointed out some good quotes on this topic.

    Probably the scientists say they just can’t imagine how one thing such as gravity can be related to some other thing like the fine structure constant, etc. But that sounds like an argument from ignorance! Isn’t there any better reason for believing the constants are independent of each other?

    • Allen Hainline says:

      Please see my most recent blog for a response to this important question. Obviously we could make some new discovery that could show some relationships of this type but it would still be remarkable if a single constant was involved in equations for other constants that somehow still resulted in values in these narrow ranges. Comment on that blog though with remaining concerns and I can try to address them.

      Here is one reason for thinking that the constants may be independent of each other:
      “we have never successfully predicted the value of any dimensionless constant in advance of its measurement.” John Barrow


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