It occurs to me that now Barnes has his book out, he may well be invited to speaking opportunities or debates and when he is, he may fall back (WLC style) on his standard arguments. In a debate, you can't go into huge detail with respect to each of your points, although you can do what is known as a Gish Gallop (proof by verbosity) and spurt out so many factoids and positional statements that your opponent cannot hope to rebut all of them in an intellectually satisfying way.
My suspicion is that Barnes will, if given the opportunity, rely on this technique. I base this suspicion on his interview with Luke Muehlhauser at the Pale Blue Dot podcast, in which he listed "11 objections" to fine-tuning.
Right, first off, there weren't 11 "objections", at best there were 10. The final "objection" wasn't an objection at all, it was the staff answer for the vast majority of people pushing the fine-tuning agenda: "god did it". And there weren't really 10 anyway, since a few of them fall into distinct categories. And not all of them were objections to fine-tuning per se, for the most part they were objections to the staff answer. One wasn't even an objection.
Let's look at the broad categories:
Denial: there is no fine-tuning, so there's no problem.
Chance: there is fine-tuning, but it comes down to chance that this universe had fine-tuning.
Necessity: there is fine-tuning, but that is just part of the way the universe is.
Design: there is fine-tuning and that was intentional.
Barnes basically Gish galloped through the first of his 10 objections which were (in Muehlhauser's words):
Chance: It’s just a coincidence
Chance (overlaid by an appeal to ignorance): We’ve only observed one universe, and it’s got life. So as far as we know, the probability that a universe will support life is one out of one!
Denial: However the universe was configured, evolution would have eventually found a way
Denial: There could be other forms of life
Necessity: It’s impossible for life to observe a universe not fine-tuned for life
Necessity and Chance/Design: Maybe there are deeper laws; the universe must be this way, even though it looks like it could be other ways
Chance: Maybe there are bajillions of universes, and we happen to be in one of the few that supports life
Design: Maybe a physics student in another universe created our universe in an attempt to design a universe that would evolve intelligent life
Chance: This universe with intelligent life is just as unlikely as any other universe, so what’s the big deal?
Denial: The universe doesn’t look like it was designed for life, but rather for empty space or maybe black holes
Design: Fine-tuning shows there must be an intelligent designer beyond physical reality that tuned the universe so it would produce intelligent life
Let's look at the necessity first. It is simply a truism to say that, in order for intelligent observers to observer a universe (from inside the universe), that universe must be conducive to intelligent observers. If the intelligent observers in question are alive and require certain stringent conditions to be met in order to remain alive then, during the period in which they observe the universe, the universe will meet these stringent conditions. This will be the case irrespective of whether the universe is designed or not.
The necessity argument is not an argument against fine-tuning, nor is it really an argument against design. At best it is an argument against the argument for design, since it effectively says "all universes with intelligent observers in them would appear designed from the inside, no matter whether they were designed or not, so mere observation of apparent design does not constitute evidence of design (nor does it constitute evidence against design)".
And if fine-tuning of the universe is a necessity, the question arises as to why it is necessary. Is it mere happenstance that the universe is necessarily the way it is, or is that by design?
There is an argument that is a combination between necessity and something else, in which the deepest laws establish fine-tuning in our universe. But the provenance of those deepest laws then becomes the question; were they established by design or do they just happen to be that way? This isn't really a separate argument, it's merely a pointless deferral of the argument.
Then there is denial. Denial is difficult to maintain, since there are so many elements of the universe which appear to be fine-tuned. Nevertheless, there have been some people who have argued that at least some of the claims regarding fine-tuning are bollocks (even I have dabbled: gravitational constant - claimed by WLC, the speed of light - claimed by Josh the Searcher). There are papers that point out that one of Barnes' favourite examples doesn't hold water (fine-tuning of the strong force). Vic Stenger wrote a book attacking many of the claims of fine-tuning. But even if denial worked, we'd still be left with an appearance of design and we could ask questions about whether this appearance was due to chance, necessity or design. If it was necessity, then this is no real argument against design and ends up resolving down to chance or design anyway, as alluded to above.
That leaves us with chance and design. At the end of the day, there are only two fundamental answers to the problem of fine-tuning, either it is mere chance that the universe is the way that it is or it was designed that way. And only one of those is an objection to design.
To be continued in Chance or Design?