The fine-tuning argument for God's existence is a failure

I thank CON for his construction of the argument, which closely follows Robin Collins (see Collins 2009). I wish to slightly modify the argument, for the sake of charity and clarity. I invite CON to correct me if I have unwittingly straw-manned his argument. CON writes, "[T]he universe is ordered in such a complex way, delicately balanced upon a razor's edge, as to allow for the existence of intelligent life…". I would like to make this explicit: Theism does not predict 'Fine Tuning' as such, but rather predicts a universe fertile for intelligent life (or embodied moral agents). Call this a "Life Permitting Universe" (LPU).{1} I presume CON is using epistemic possibility to drive the probability inference. So, when CON writes "[I] will argue that the universe and all its constants and conditions, under the principle of indifference, could have been different." I take him to be saying that it is epistemically possible for the universe to have different values for its constants and conditions (and, given indifference, they should be weighed equally). This appears the most defensible way of cashing out these possibilities - if CON had a better idea in mind, he is welcome to offer it. We now have: P(LPU|T & k') >> P(LPU|ASU & k') LPU: Life permitting universeT: TheismASU: Atheistic single universe{2}k': our background knowledge, subtracting (inter alia) knowledge of our existence or this universe existing. {3} Con is surely right to say the universe is 'delicately balanced' for Life Permitting-ness: across the epistemic space of possible values for these constants and conditions could take, the life permitting range appears miniscule. On Atheism (given indifference), the likelihood of landing in this miniscule range is as remote as any other miniscule range in the probability space (nothing turns on just how small this is - call it "one in a zillion"). Theism, by contrast, predicts a life permitting universe, as embodied moral agents or similar are part of God's design plan.{4} So, P(LPU|T&k') >> P(LPU|ASU&k'), and that a life permitting universe obtained provides stonking good confirmation of Theism. How can this argument be a failure? Epistemic access and modal explosion Best science tells us that mild deviations of the constants and conditions would result in a universe that is not life permitting. It is silent about massive deviations - if, for example, a universe with some of the constants and conditions shifted by a few million orders of magnitude would be life permitting. We cannot reliably extrapolate our physical understanding out that far. The space of possible worlds with wildly divergent values is bigger than the space of possible worlds with values close to our own. There are further limits to our epistemic access. Consider these possibilities: Alien Physics (friendly): There is a set of physical laws entirely dependent on four variables, A, B, C, D. A-D can range over the positive reals. For all combinations of A-D, the resulting universe is life permitting. Alien Physics (unfriendly): There is a set of physical laws entirely dependant on a million variables, all of which can range over the positive reals. Only the instance where each of these million variables equals one is the resulting universe life permitting. Both alien physics, friendly or unfriendly, strike me as epistemically possible (it strikes me as epistemically possible, albeit remotely, that this universe could be one or the other - our best physics might be mistaken). One can conceive of more and more alien physics, to varying degrees of life friendliness, ad infinitum. From this, it is clear that the possibility space is exploded far beyond our means of epistemic access: we only have reliable insight into the locality around our universe, not those with wildly different constants or laws of physics. In this far larger region of the probability space, the incidence of LPUs is inscrutable. For the fine tuning argument to work, we need to assign P(LPU|ASU&k') as low - that life permitting universes are rare across all epistemic possibilities of how the universe 'could have been different'. Yet the fact that LPUs are rare in the tiny scope of possibilities we can examine provide no warrant to suppose that they are rare across the entire probability space, the vast bulk of which we do not have access to examine. If so, then the correct assignment for P(LPU|ASU&k') is that it is inscrutable. Therefore, whether it is less than P(LPU|T&k') is also inscrutable. Therefore, the fine tuning argument provides no confirmation for Theism over Atheism. Consequently, the fine tuning argument is a failure.{5} Conclusion CON may accuse me of having a modally promiscuous imagination: that alien physics or wild constants are impossible. It is hard to see why this would be so: there seems no warrant for thinking the space of epistemically possible universes comprises primarily of those with laws of physics like our own, and values for the constants not too far from our own. The problem is the possibilities I leverage to show the fine tuning argument is a failure are no more remote than those CON relies upon to make the argument in the first place. I have closely addressed CONs original presentation, at the expense of a more general overview of fine tuning arguments. Might it be the case that this objection applies only to this particular form of the fine tuning argument, but the argument succeeds in other guises? This is unlikely - this presentation is the clearest iteration of the fine tuning argument (Craig's, for example, is far more clumsy, see e.g. (Craig, 2007 pp. 78), and the objection - that we lack access to say life permitting universes are rare on Atheism - will be applicable no matter how we cash the argument out. If any fine tuning argument can survive this objection, then this fine tuning argument can survive this objection. But it cannot. Thrasymachus {1} Also, "fine tuning" is a bit vague, and risks confusing the argument I think my opponent is making with subtly different ones (for example, (Roberts, 2011)) {2} I will grant for the sake of argument that multiverses are not a serious possibility. {3} This is included for little more than completeness's sake, although subsequent developments will make it relevant. See (Collins, 2005) for a programme of how this 'subtraction' may occur. {4} It does not strike me that P(LPU|T) should be very high: it is not clear to me why God would want worlds of embodied moral agents rather than aphysical spirits, for example. Regardless of my worries, P(LPU|T) is not that low - certainly greater than one in a zillion to derive confirmation from the fine tuning argument. I note this now only because it may be relevant later.{5} I reject CON's assertion that "[M]y opponent must show that … the probability of theism is not increased even if all my premises are true". What I originally said was "An argument is a failure iff, after considering the argument, it would not be reasonable to raise one's credence in the conclusion of that argument. In other words, the argument does nothing to make what it is arguing for more probable or plausible." CON misquotes me by omitting the part in italics. Yet even if that was a fair redaction, CON's exegesis is crazy: formal validity is insufficient to "make what it is arguing for more probable or plausible". Here's an example of a formally valid fine tuning argument that fails to make its conclusion more plausible: If there is fine tuning of the universe, then the moon is made of cheeseIf the moon is made of cheese, then God existsThere is fine tuning of the universe//God exists So I don't need to show CONs argument to be formally invalid - I can settle for showing key premises to be false or inscrutable. If my argument that we have no access to make the probability assignments CON requires prevails, then the fine tuning argument is a failure (on this, cf. (van Inwagen, 2006. Ch. 3)).