Perhaps the worst (published) straw-man argument against cosmological fine tuning as an apologetic. Ever.

Consider this 2005 paper Problems with the argument from Fine Tuning by Colyvan, Garfield, and Priest. ¹ Its abstract:

ABSTRACT. The argument from fine tuning is supposed to establish the existence of God from the fact that the evolution of carbon-based life requires the laws of physics and the boundary conditions of the universe to be more or less as they are. We demonstrate that this argument fails. In particular, we focus on problems associated with the role probabilities play in the argument. We show that, even granting the fine tuning of the universe, it does not follow that the universe is improbable, thus no explanation of the fine tuning, theistic or otherwise, is required.

Note that this is not a physics or cosmology paper. It is a rather clumsy philosophy-probability paper. They make so many mistakes that by the second page that I can hardly believe what I am reading.

They begin by stating the fine-tuning argument with, in their words, “precision”:

(1) The boundary conditions and laws of physics could not have been too different from the way they actually are if the Universe is to contain (carbon-based) life. 

(2) The Universe does contain (carbon-based) life

Fine-tuning makes no such claim as (1). The fine tuning claim is this: our universe’s constants could not change much from their given values without destroying habitability. It is the claim that in the multi-dimensional parameter space of physical constants, we are sitting on an unstable equilibrium–like a ball resting on a mountain peak. It does not does not claim that there are no other mountain peaks, or stable equilibria (valleys), or vast plateaus of stability– it only claims that a small step from our position in this parameter space is calamitous.

Let me say this again: the fine tuning argument does not rule out the possibility of other sets of constants, very different from our own, producing habitable universes. It merely states that small excursions from where we are would result in a loss of habitability.

Then the authors give the unsubstantiated and dreaded probability claim as a hence:

Hence: (3) The Universe as we find it is improbable.

There is no such hence. The fine-tuning argument makes no claim with regard to the probability of our universe. It only makes a claim, be it right or wrong, about the sensitivity of the habitability of our universe to small changes to the constants.

Fine-tuning proponents cannot make a claim about the probability of our universe, even if they wanted to, because nobody knows how to calculate such probabilities.

The authors then do the inevitable:  they make a gratuitous connection to the religious co-opting of the fine-tuning argument:

(4) The best explanation for this improbable fact is that the Universe was created by some intelligence.

Hence: (5) A Universe-creating intelligence exists.

They have either no knowledge or no regard for the fact that the fine-tuning problem is viewed as a serious physics puzzle by secular scientists who do not connect it to a religious argument.

You could easily replace, with as much legitimacy, (4) and (5) by

(4’) The best explanation for this improbable fact is the multiverse

(5’) No universe-creating intelligence exists.

Their paper has the goal of showing that (3), above, does not follow from (1) or (2). Which is an exercise in irrelevancy. We can readily stipulate that (3) is not a consequence of (1) and (2). But by demonstrating that that (3) is not a consequence of (1) and (2) they have, in their own minds, neutered fine-tuning.

OK… let’s roll with it. Maybe they can provide some value to the community by proving that (3) does not follow. It won’t make any difference to the fine-tuning argument, but it would be at least interesting in its own right. Can they provide a convincing argument? They have an argument, and it leads to the stunning conclusion:

The fine tuning argument, on its most plausible interpretation, hence not only shows that life-permitting universes are improbable, but, arguably, that they are impossible!

Now that would be something! (Although again, it is not an argument at all relevant to fine tuning.)

How did they prove such a stunning result in a mere two paragraphs on p. 327? With some of the worst analysis I have ever seen published. To paraphrase (read it if you think I am being uncharitable) they argue that if a constant k can have any real value (which, by the way, nobody claims, but OK) , then any finite range of possible values (even big ranges, let alone the small ranges demanded by fine-tuning) has effectively a zero probability. Therefore, they conclude, improbable habitable universes are, in fact, impossible.

I’m not kidding, that’s their argument.

I’m pretty sure that they don’t relealize that a high probability universe (esp. P = 1) with fine-tuning (sensitivity) is a much stronger religious apologetic than a low probability universe. Why? Because it undermines a secular solution of the fine-tuning problem based on large numbers (the multiverse) which, though presently unfalsifiable, does indeed "explain" why we are in the perfect puddle for our own existence. The non-religious multiverse answer is inextricably tied to a low probability universe. (Do the authors realize that if they are right they have not shredded the religious apologetic, but the secular one?)

A high probability universe, in which our constants were somehow inevitable, would be a major victory for the theists, who could rightly claim that habitability was built into the fabric of spacetime.

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¹ Colyvan M., J. L. Garfield, and G. Priest, 2005, “Problems with the argument from fine-tuning”, Synthese, 145(39): 325–338.