Design's Last Stand
I finally finished Leonard Susskind's book The Cosmic Landscape: String Theory and the Illusion of Intelligent Design. Susskind's main argument is that the universe as we know it is just one small piece of a vastly larger landscape inhabited by something like 10^500 different pocket universes. The laws of physics can vary from universe to universe. If this is correct, it provides a satisfying explanation for the apparent examples of fine-tuning we find in the fundamental constants of our own universe. Why does our universe appear to be so well-suited for life? Because if it weren't we wouldn't be here to ask the question. And if you get 10^500 tries to get it right, there is bound to be some corner of the landscape where the constants will work out the right way.
I won't attempt a full review of the book. Overall I liked it quite a bit, but there are also a lot of small problems along the way. My main criticism is that as an explainer of difficult ideas from physics, Susskind can't hold a candle to Brian Greene.
But his main argument strikes me as very satisfying on two fronts. First, the main rival to Susskind's idea is that the fine-tuning of the universe represents the action of an intelligent designer. This idea is based on nothing more than people's desire that it be true. Susskind's idea, by contrast, arises naturally from modern String Theory. Susskind writes (in a discussion of the idea of Eternal Inflation):
The bubbling up of an infinity of pocket univerdses is as certain as the bubbling of an opened bottle of champagne. There are only two assumptions: the existence of a Landscape and the fact that the universe started with a very high density of energy, i.e., that it started at high altitude. The first may prove to be no assumption at all. The mathematics of String Theory seems to make the Landscape unavoidable. And the second - high energy density - is a feature of every scientific cosmology that begins with the Big Bang. (p. 304)
I also liked this:
In any case the difficulties in testing the Landscape, Eternal Inflation, and the Anthropic Principle are real, but there are many ways to test a theory. Mathematical consistency may not impress the most hard-nosed experimental physicist, but it should not be underestimated. Consistent theories that combine quantum mechanics and general relativity are far from common. Indeed, this is the reason that String Theory has so little competition. If no alternatives show up and if String Theory proves to have as varied a Landscape as it seems, then the populated Landscape will be the default position - the theory to beat, so to speak. (p. 375)
So the choice between ID and the Landscape is the choice between an explanation made up out of whole cloth for its emotional value on the one hand and an explanation that makes sense out of such data as we have on the other. String theory can hardly claim to have proven itself correct, but it has a lot going for it.
The second reason I find the Landscape appealing is that it fits so well with everything else we have learned from science over the years. Everything science has been telling us has been in the direction of downplaying the metaphysical significance of our existence. Comparative anatomy reveals to us that there is nothing in our physical make-up to distinguish us from the animals. Neuroscience can find nothing to support the idea that the mind exists separately from the brain. Evolution shows that we are just one more species among many, formed by the same processes that formed every other species. And we did not arise in a puff of smoke in one moment of creation, but rather as one end result of a billion year process; a process, no less, that gives no indication of having had us in mind. Astronomy shows that the Earth is not the center of it all. Rather we are just an unremarkable planet orbiting a nondescript star; one of countless solar systems in countless galaxies that litter the universe.
And now here comes the Landscape to show us that even our universe is not distinguished in any important way. That is why I have titled this blog entry the way that I have. The relentless march of science over the last few centuries has been paralleled by one ignominious retreat after another for the design argument. Today design advocates can only play one, last, desperate card - the fine-tuning of the constants. Upon this one puzzling phenomenon they base their conclusion that despite all the evidence to the contrary, humans are still the point of it all. Can any thoughful person seriously believe such a thing?
And is there any argument at all - I'll take one! - for rejecting the Landscape, or more generally, the megaverse? Can the other side offer any actual reason for thinking that we are not part of a vast Landscape? It certainly can't be that we have no direct evidence of the existence of other universes. After all, we have no direct evidence for the existence of God either, but ID folks are quick to assure us that it is the height of rationality to believe it nonetheless.
Susskind himself points out some unsolved problems with the Landscape, and he also points to ways we might possibly, someday, be able to experimentally test various aspects of his theories. So it is possible that String Theory and its logical correlates will eventually fail the only test that matters - fit with experimental data. But until that day comes the Landscape has to be regarded as vastly more probable than ID. Even if some people find that idea unpleasant.