It's a review of Many Worlds in One: The Search for Other Universes by Alex Vilenkin.
There's a lot of interesting ideas going on there: Vilenkin speculating that we live in an infinite multiverse, Vilenkin embracing the Many Worlds Interpretation for whatever reason... of course, what turns Craig's head is the following:
It is said that an argument is what convinces reasonable men and a proof is what it takes to convince even an unreasonable man. With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape, they have to face the problem of a cosmic beginning" (p. 176).
Given that everyone who knows about WLC knows that the Kalam Cosmological Argument is one of his favorite arguments, you can see why Craig's writing such a review of this book. No matter what else Vilenkin may say, that's a feather in Craig's cap.
Now, there's two other things I want to point out. One today, one tomorrow. First this quote by Vilenkin, while talking about the ramifications of multiverses, in his view.
In the worldview that has emerged from eternal inflation, our Earth and our civilization are anything but unique. Instead, countless identical civilizations are scattered in the infinite expanse of the cosmos. With humankind reduced to absolute cosmic insignificance, our descent from the center of the universe is now complete (p. 117).
There are a lot of ways to pick apart this view. One, of course, being: Since when is being infinite in number a downgrade of importance? This is back to the "if God existed, the universe would be smaller / bigger!" argument, always one of the weakest around. No point spending time on it.
But, there's another problem. If we're going to play the multiverse game, well.. let's play. And Paul Davies has something interesting to say about the board:
These are murky waters, but they get even murkier when we scrutinise what is meant by the words "exist" and "real". In the Tegmark multiverse of all possible worlds, some worlds will have intelligent civilisations with computers powerful enough to create authentic-looking virtual worlds. Like in the movie The Matrix, it may be almost impossible for an observer to know which is the real world and which is a simulation. And if the simulation is good enough, is there any fundamental difference between the two anyway?
It gets worse. Mathematicians have proved that a universal computing machine can create an artificial world that is itself capable of simulating its own world, and so on ad infinitum. In other words, simulations nest inside simulations inside simulations ... Because fake worlds can outnumber real ones without restriction, the "real" multiverse would inevitably spawn a vastly greater number of virtual multiverses. Indeed, there would be a limitless tower of virtual multiverses, leaving the "real" one swamped in a sea of fakes.
So the bottom line is this. Once we go far enough down the multiverse route, all bets are off. Reality goes into the melting pot, and there is no reason to believe we are living in anything but a Matrix-style simulation. Science is then reduced to a charade, because the simulators of our world - whoever or whatever they are - can create any pseudo-laws they please, and keep changing them.
In other words, Vilenkin - at least by this interview - hasn't quite dropped us at rock bottom yet after all. Turns out there's still one more infinite drop we can be placed in, at least given his views and metaphysics: Downward. Not spatially, but in a simulation sense. Our fall isn't 'complete' unless we're in a simulation (of a simulation, of a simulation, of a...)
Of course, Vilenkin can walk through that door if he so wishes - Davies would say his theory practically demands it. But as Davies points out, the price to pay for that is a reductio of his position, in the form of dashing science once and for all. It turns out we haven't been studying 'nature' all this time after all. Nature's the next floor up on the elevator, so to speak. Chances are we're studying someone's computer simulation - and we're all Intelligent Design advocates now!
Amusingly, if Vilenkin (or others) would even try to refute this, they'd suddenly be changing their tune. Something along the lines of, "Sure, we're insignificant - but not THAT insignificant!"
What I'd really like to know is: Where would the Copernican Principle place us, given the prospect of simulation and Vilenkin's multiverses? Again, the answer's bound to be interesting.
Anyway, quite a lot can be said about what Vilenkin is discussing. (Such as, what are the prospects of 'reason' in the universe as pictured by Vilenkin?) But I'm picking up two themes. One is the multiverse/ID aspect. The other.. well, tomorrow, hopefully.