A Users Guide to the Fine-Tuning Argument for the Existence of God

Update: This article is now one of Part 2. In Part 2, further objections are considered.

This approach is utilized in worldview debates: asking whether some data is more likely given some theory versus without that theory.

A worldview is a sort of total picture of reality. Classical theism, for example, is a worldview; naturalism is another. The former is marked by a principle of perfection or pure actuality at the foundation of everything, the latter by a principle of indifference. (See recent discussions on worldview comparison here and here; this discussion is an extension of those.)

Fine tuning — one of the relevant data points considered in worldview debates — is defined by physicist James Sinclair as follows,

“This expression refers specifically to fine-tuning for the emergence of life within our universe—or within any universe with physical laws similar to those of our universe. An instance of fine-tuning for life occurs if a free parameter has a value needed for the emergence of life-forms, and if such a value is exceedingly improbable within the total available parameter space of our universe. So, for example, if the total free parameter space for the values of a given free parameter (say, the electromagnetic charge or the Q nonuniformity of mass-energy density) could be mapped on a grid that is three miles by three miles, but the parameter space permitting life is only one millimeter by one millimeter on that grid (exceedingly improbable), and the value of the free parameter in our universe just happens to fall within that relatively small area, it appears to be an instance of fine-tuning for life. The fact that this free parameter just happens to have an exceedingly improbable value needed for life and that it is not necessitated or predicted by any physical theory (or the laws underlying that theory) requires a causal explanation beyond a one-off pure chance (which is virtually unrealizable).”

Further appreciation of fine-tuning is accomplished through additional expert testimony.

Consider, for example, the following from physicist John Polkinghorne,

“Four fundamental forces of nature operate in our universe. Their intrinsic strengths are determined by the values of four corresponding constants of nature. … The magnitudes of all these constants are tightly constrained if the universe is to be capable of producing life. If [one of these] were a little smaller, the early universe would have converted all its hydrogen into helium before it had cooled below the temperature at which cosmic nuclear processes ceased. Not only would this have meant no water, so essential to life, but there would also only have been helium-burning stars, which would not have lived long enough to support the development of life on one of their planets. If [it] had been somewhat bigger, supernova explosions would have been inhibited.”

The following from physicist Luke Barnes,

“… A universe that has just small tweaks in the fundamental constants might not have any of the chemical bonds that give us molecules, so say farewell to DNA, and also to rocks, water, and planets. Other tweaks could make the formation of stars or even atoms impossible. And with some values for the physical constants, the universe would have flickered out of existence in a fraction of a second. That the constants are all arranged in what is, mathematically speaking, the very improbable combination that makes our grand, complex, life-bearing universe possible is what physicists mean when they talk about the ‘fine-tuning’ of the universe for life.”

Finally, as astronomer Fred Hoyle once remarked,

"If this were a purely scientific question and not one that touched on the religious problem, I do not believe that any scientist who examined the evidence would fail to draw the inference that the laws of nuclear physics have been deliberately designed … A commonsense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as with chemistry and biology.”

It has often been claimed that fine-tuning is astronomically more probable if God exists than if God does not exist. The argument being our discovery of fine-tuning should afford enormous credence to the classical theistic hypothesis over the naturalistic hypothesis.¹

For example, philosopher Michael Rota has issued a powerful demonstration, using the standard Bayesian formula, focusing on just one aspect of physical fine tuning (namely, that the effective cosmological constant falls within the life-permitting range) to show one would have to have a lower prior expectations of God down at over 1 over 10^32 (meaning they would have to think the existence of God is that unlikely before considering the evidence of fine-tuning) to neutralize the force of the fine-tuning evidence in favor of theism.[1] What this means, for all intents and purposes, is that from physical fine-tuning alone one should be extremely confident – i.e., virtually certain – that God exists.[2] That is, from Rota’s calculation, one could argue that physical fine-tuning can more than pay all probabilistic debts a naturalist might accrue against the theism in evidential cases, including the problem of evil. Fine-tuning is that probabilistically persuasive toward theism. Or so certain philosophers and scientists claim.

With those preliminaries aside, the remainder of this article is to highlight what I believe are the most important aspects of the fine-tuning debate. Given this just is an article — really, a blog post — not everything can be covered.

So, when it comes to naturalistic attempts to address the force of the fine-tuning argument, I consider the most interesting to be:

• First, the suggestion that fine-tuning is neither the result of design nor chance but necessity.

• Second, multiverse proposals, bringing back the chance alternative.

• Third, to concede the force of fine-tuning for theism but suggest it is outweighed by other considerations for naturalism, such as the problem of evil.

• Fourth, that theism predicts fine-tuning no better than naturalism because God’s will is inscrutable, which means we cannot have any realistic expectation that God would create a universe like ours.

The third consideration I will not have much to say on since that concedes the overall point about fine-tuning favoring theism but then shifts the debate to other territory. (There is one objection later that falls under this category, however.)

Let’s start with the first proposal — namely, that fine-tuning is neither result of design nor chance but necessity. Perhaps some will say that if fine-tuning is part of some initial segment of physical reality that is itself necessary, then that fine-tuning is necessary as well.[3]

Here are two reasons I think this response is not a good one. First, from the best of our knowledge, it seems fine-tuning is not necessary. After all, physicists can mathematically model many universes with different parameters that appear perfectly coherently, which is reason to think this universe is not the only possibility, and thus not necessary. It seems that to support this necessity proposal one must adopt a rather ad hoc account of modality, which would damage our modal intuitions moreover since it really seems – for all we know – that things could have been otherwise in this respect. Either way, this objection ultimately fails, since the necessity proposal does little to alleviate the evidential force of fine-tuning in favor of theism once one makes the distinction between metaphysical and epistemic possibility, as philosophers like Rota have pointed out. Details of this distinction are found in Rota’s published work (footnoted) for the interested reader, but the simple, summary point is this distinction ultimately renders the necessity objection toothless by showing that fine-tuning provides powerful evidence not just that there was a designer involved but that the relevant fine-tuning is contingent.[4]

What about God’s will being inscrutable? There are various ways of addressing this objection, most of them harmonious, I think. First, there is the path of working through the notion of omnipotence to omniscience and ultimately to motivation theory (effectively Richard Swinburne’s approach); or more traditionally stated, God, in perfectly understanding himself as the fullness of being, understands all the ways anything else could exist and that it would be good for them to exist. Quite obviously, beings like us are extremely good and God would know this and be motivated by it. How motivated? Like Rota and Swinburne, I suggest a modest likelihood of God creating beings like us is 50%. However, in Rota’s calculations (which affords an enormous credence to theism from fine-tuning) he affords the skeptic the exceedingly generous estimate of God creating beings like us being just 1 in a billion!

There are other considerations of course, including the diffusiveness principle and plentitude principle, as long maintained within the classical theistic tradition though more recently defended by thinkers like Norman Kretzman, Joshua Sijuwade, Norris Clarke, and David Oderberg. These notions are simple, intuitive, and typically linked: first, that the very notion of goodness is one of self-communication or diffusive. The good naturally seeks to diffuse itself, sharing its goodness with others. Second, that God being the supreme good – literally subsistent goodness itself – would, by nature, seek to diffuse his goodness as well through a vast hierarchy of being (principle of plentitude), which would ultimately include, if not culminate in, beings like us. Again, read the mentioned authors for further development of these two principles. The point now is these principles are not contrived but rooted independently within the classical theistic metaphysical tradition and build a strong anticipation that God would create beings like us. The objection from God’s will being inscrutable largely ignores these considerations and is too skeptical. One needn’t grasp the essence of God for reason to reveal that God would have strong motive to create, especially to create beings like us (which entails a fine-tuned universe).

But we can go further. Because Rota helpfully draws another distinction, namely between,

(a)   P(the universe is life-permitting | God exists), and

(b)   P(the universe is life-permitting | the universe was caused by God).[5]

As Rota elaborates,

“To evaluate P(X|Y), one takes it as given that Y is true, and then estimates P(X). So to evaluate (a), one would take it as given that God exists, but not take it as given that God has chosen to create anything at all. In contrast, to evaluate (b) one would assume that God has caused the universe to be and then ask how much one could expect the universe to be life-permitting. So if one were discussing (b), questions about how likely God is to create anything at all are irrelevant. The question is whether God (or more generally any universe-designer) would make the universe life-permitting, supposing that the universe-designer was already going to make the universe. In the FTA as presented above, P(E|D) is akin to (b), not (a). In order to evaluate P(E|D), one takes it as given that the universe is the causal product of an intelligent being (and hence one assumes that the universe-designer has already produced the universe). One then asks how much it would be expected that the cosmological constant would be life-permitting. Is P(E|D) inscrutable?”[6]

And of course, it is not inscrutable, since we know of a good reason for the cosmological constant to fall within the life-permitting range – it is necessary for the emergence of beings like us, which are extremely good. Thus, it is quite expected that if the universe is God-produced the cosmological constant would fall within the life-permitting range.

In sum, it seems to me that the inscrutability objection can be overcome.

Moving on now to what I believe is the most interesting objection, which is the multiverse objection. In short, the most prominent naturalistic explanation for fine-tuning is the multiverse theory, which posits an enormously, perhaps infinitely, large number of universes (each resulting, say, from some universe generator), with the notion being that probably, if not inevitably, you wind up with a universe like ours. From there, we just happen to be the lucky ones.

As skeptical philosopher Michael Ruse puts it,

“The fact that it is our universe or part of the universe in which there is life is no more improbable than that someone holds a winning lottery ticket. Given enough rolls of the dice or the drum, there was bound to be a winner eventually. The same with livable universes. Obviously, if we didn’t have the winning ticket, we wouldn’t be around to tell everyone about it. That’s no miracle, any more than that the person who won the lottery is the person who quits work and goes to live in the south of France.” [7]

There are, however, problems with the multiverse proposal; several of them insuperable.

The first is pretty simple: namely, that just positing an infinite number of universes, without qualification, fails to solve the larger issue, since that could mean an infinite number of non-finely tuned universes – that is, non-finely tuned for life like us. An infinite number of something is no guarantee you’ll get what you want – you could just as well have an infinite number of universes with just one particle. Nor will it do to posit a multiverse theory which includes all possibilities, since, as Joshua Rasmussen points out, this is contradictory: “The possibility that all reality is empty preclude the possibility that some parts of reality are not empty.”[8]

The fundamental issue is that any theoretically workable multiverse proposal itself requires specification and fine-tuning, which only relocates the problem rather than solves it.

As physicist Robin Collins summarizes the point,

“… in all current worked-out proposals for what this ‘universe generator’ could be—such as the oscillating big bang and the vacuum fluctuation models explained above—the ‘generator’ itself is governed by a complex set of physical laws that allow it to produce the universes. It stands to reason, therefore, that if these laws were slightly different the generator probably would not be able to produce any universes that could sustain life. After all, even my bread machine has to be made just right in order to work properly, and it only produces loaves of bread, not 12 universes! Or consider a device as simple as a mouse trap: it requires that all the parts, such as the spring and hammer, be arranged just right in order to function. It is doubtful, therefore, whether the atheistic many-universe theory can entirely eliminate the problem of design the atheist faces; rather, at least to some extent, it seems simply to move the problem of design up one level.”[9]

Moreover,

“Even if an inflationary/superstring many-universe 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. In the absence of alternative explanations, the existence of such a system counts as evidence for design since it seems very surprising that such a system would exist with just the right components under the hypothesis that the universe exists as a brute fact without any explanation, but not surprising under the theistic hypothesis. Thus, it does not seem that one can completely escape the evidence of design merely by hypothesizing some sort of many-universe generator.”[10]

Second, it goes without saying that the multiverse comes with an impressive increase of ontological commitments (a strike against quantitative simplicity, minimally). Perhaps this is not terrible however, if the ballooning number of entities are not basic or fundamental. Still, for the multiverse theory to generate such a range of universes to eventually wind up with one like ours, requires that theory to be rather very complicated which just reinvites or more likely confounds issues we’ve discussed in previous posts concerning whether theism or naturalism is a simpler overall theory.   

Third (consider this a bonus), is the issue of “freak observers” and the various skeptical scenarios this invites. As Spitzer and Sinclair summarize the issue,

“Continued advocacy of a multiverse under an atheist definition of mind (where the brain just is the mind), will lead to increasing skepticism—from Boltzmann brains to brief brains, and then, it seems necessary, to “Boltzmann robots” (machines that can pass a Turing test; see Banks 2012). Ultimately, cosmologists will saw off the branch on which they are sitting and produce the purest form of skepticism, and, perhaps, rule out cosmology itself. In view of this, it seems unlikely that the multiverse will provide an ultimate explanation for fine-tuning—even into the future.”

I cannot elaborate this concern here. For readers unfamiliar with freak observer problems, I recommend the article Our Universe from Spitzer and Sinclair as featured in this unfortunately priced volume.

OK, some remaining objections.

Philosophers like Ruse are ready with another retort: “Are we convinced that the only kind of life-form we know – carbon-based and so forth – is the only viable life-form? What about the Horta in Star Trek?”[11]

As Collins said about this objection years before Ruse raised it,

“Another objection people commonly raise to the fine-tuning argument is that as far as we know, other forms of life could exist even if the parameters of physics were different. So, it is claimed, the fine-tuning argument ends up presupposing that all forms of intelligent life must be like us. The answer to this objection is that most cases of fine-tuning do not make this presupposition. Consider, for instance, the case of the fine-tuning of the strong nuclear force. If it were slightly larger or smaller, no atoms could exist other than hydrogen. Contrary to what one might see on Star Trek, an intelligent life form cannot be composed merely of hydrogen gas: there is simply not enough stable complexity. So, in general the fine-tuning argument merely presupposes that intelligent life requires some degree of stable, reproducible organized complexity. This is certainly a very reasonable assumption.”[12]

We’re almost done. What about the objection that says: fine-tuning doesn’t require an explanation, because if the universe wasn’t fine-tuned, we wouldn’t be here to ask about it. In other words, the universe must be fine-tuned since that is the only universe where we could discover fine-tuning (after all, you couldn’t exist in a universe not fine-tuned for your existence).

While common enough, this objection is not a good one. Obviously, we could not be aware of fine-tuning if the universe were not fine-tuned; nobody denies that. So, fine-tuning must occur for us to raise questions about. That, however, does not itself explain the occurrence of fine-tuning, even if it explains how we came to discover fine-tuning. Common comparison: you’re set to be executed by a firing squad of 100 sharpshooters. Somehow, after all the shots are fired, you survive. Against all odds, not a single bullet hit you. Obviously, if you didn’t survive, you wouldn’t be able to ask the question – however did I survive the execution attempt? That said, your being alive does not explain why you survived the execution attempt. Surely, it is reasonable to demand explanation of this, and likely that explanation has to do with the execution attempt being something of a put on (someone giving the command for all the shooters to miss, say).

Other moves? At this point, the skeptic could accept the probabilistic force of fine-tuning in favor of theism but respond (as some naturalists have) that quantum cosmology gives counter evidence for atheism, since it implies only the probability of a life-permitting universe and not the certainty thereof, alongside the claim that this would be an irrational way for God to create. Unfortunately for the skeptic, this objection assumes too much including that God doesn’t have control over outcomes based in natural propensities: of course, God, given that God creates and sustains all nature(s) in existence, can hit whatever outcome He wants with certainty. As Rob Koons says, “What exactly is irrational about God's creating a condition C with the natural propensity of producing E with probability p (<1), and then actualizing E with probability 1? I suppose God does that sort of thing all the time. Presumably there was some small, finite probability that the water of Lake Galilee would support Jesus' weight in an upright position, but God intervened so as to bring about this result with probability 1.”[13]

Finally, one might ask if positing God just relocates the issue as well, for wouldn’t God be something quite complex and requiring a designer, as well? For those who’ve studied the cosmological argument the answer to this query is obviously, “no.” Cosmological reasoning tells us God is in no way complex, either physically or metaphysically. Given divine simplicity, God’s act and object of understanding are identical – God has no parts that require coordinating, nor is God directed toward some end other than himself by anything beyond himself. This shows the explanatory superiority of classical theism as it escapes the concern of positing something more complex (in the sense of requiring extrinsic explanation) than the phenomena before us yet is still something with intellectual capability, which is the best if not only possible explanation of physical fine-tuning.

In summary: even when strapped with greater complexity, naturalism fails to provide as good an explanation of physical-fine tuning as theism does, since theism is more predictive of fine-tuning than any naturalistic variant, including multiverse scenarios. While much more can be said about the fine-tuning debate, my evaluation is physical-fine tuning is far better explained by theism than naturalism and provides overpowering confirmatory weight in favor of a theistic worldview.[14] So much evidentiary weight, in fact, that considerations from fine-tuning should be enough to confirm a person in theistic belief, even if granting substantial evidential weight in favor of atheism from other considerations.

Further Resources

If I were to recommend just three resources on this debate, they would be…

Luke Barne’s A Fortunate Universe. Robin Collins contribution in The Blackwell Companion. Finally, Michael Rota’s Taking Pascal’s Wager.

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[1] See, Michael Rota’s Taking Pascal’s Wager

[2] Importantly, Rota’s calculation considers the suggestion that physical fine tuning was necessary rather than contingent. Rota shows the necessity objection does ultimately virtually nothing to block the enormous evidential weight fine-tuning provides for the existence of God.

[3] Graham Oppy seems to make a proposal along these lines.

[4] See Taking Pascal’s Wager, 121-126, and particularly note 6, for the mathematically inclined.

[5] The Fine-Tuning Argument as featured in https://www.amazon.com/Contemporary-Arguments-Natural-Theology-Rational-ebook/dp/B097P8FPQN

[6] Ibid.

[7] Taking God Seriously: Two Different Voices, pg. 72.

[8] Is God the Best Explanation of Things, 145.

[9]See:  https://rintintin.colorado.edu/~vancecd/phil201/Collins.pdf

[10] Robin Collins, “The Many-Worlds Hypothesis as an Explanation of Cosmic Fine-Tuning: An Alternative to Design?” Faith and Philosophy 22:5 (Special Issue 2005): 654-666, 659.

[11] Taking God seriously, pg. 73.

[12] Robin Collins The Fine Tuning Design Argument: https://rintintin.colorado.edu/~vancecd/phil201/Collins.pdf

[13] See: https://robkoons.net/uploads/1/3/5/2/135276253/sobel_review_logic_and_theism.pdf

1. Assuming, of course, these two hypotheses form a partition, which many contend is not the case. What about animism or polytheism or maltheism or whatever else? Could fine-tuning not point in their direction just as well as classical theism? The short answer, I think, is not really – or at least not as heavily – but to evaluate that would mean unpacking the expectations of each of these hypotheses systematically, which is not something we have adequate time for, here. For now, I think we can safely set that complication aside, because it seems most people do not seriously entertain these alternative worldview theories. After all, I am not sure the last time I met a living polytheist and maltheism is almost never proposed apart from (never very good, in my estimation) parody attempts. More realistic are considerations of pantheism or panentheism. Perhaps, then, it is the case that fine-tuning gets us to just a more general form of theism, even if further work must be done to move toward classical theism particularly. I don’t see that as a problem, however. Progress is still progress.