Saturday, 12 January 2013

Occam’s Razorburn

Stephen Hawking’s latest book raises far more questions than it answers. Such as, why hasn’t he been reading Thomas Kuhn, and what really is the benefit of unifying theories which don't seem to need unification?

In which we meet yet another first-class scientist who wishes to self-identify as a second-class philosopher and a comedian from the back end of steerage.

Since few will buy A Grand Design for its wit we can forgive Stephen Hawking's appalling attempts to be funny, but it's not so easy to forgive his philosophical ignorance. Certain physical scientists might be better off unacquainted with the modern philosophy of science (though those who know it possess a welcome sense of perspective and humility). But not world-renowned cosmologists. Their field continually bumps up against the boundary of what science even is (and it doesn't have a "no-boundary condition", whatever that might be).

So when Stephen Hawking claims that "philosophy has not kept up with modern science, especially physics" it suggests not only a lack of perspective and humility, but that Hawking has been skipping on some required reading.  Especially since, having written off the discipline, Hawking seems barely acquainted with it. He mentions few philosophers more recent than Rene Descartes (d. 1650). So it is hard to know who he thinks hasn't kept up.

Particularly when Hawking's first grand pronouncement is "model-dependent reality": the idea that there may be alternative ways to model the same physical situation with fundamentally different elements and concepts. "If [such different models] accurately predict the same events, one cannot be said to be more real than the other." Physics has, apparently, been forced into this gambit following recent failures to get unifying calculations to work themselves out. In any case it isn't quite the neat trick Hawking thinks it is.

Firstly, while model-dependent reality might be news to Stephen Hawking (he seems to think it the fruit of modern physics' womb) the philosophers he hasn't been reading have been talking about it for years, if not centuries, to the constant sound of scientists' excoriations. It is even part of Descartes' philosophical fabric (and, more tellingly, Darwin's, but picking a fight with modern evolutionists, while fun, is a story for another day). That is to say, it sounds like it is the physicists who are finally catching up with the philosophers and not the other way around.

Secondly, in the grand game of philosophers' football that Cosmology has become, the model-dependent reality play is something of a surrender before kick-off.  For if it is true that the same phenomenon can be plausibly accounted for in multiple, "incommensurate" (© Thomas Kuhn) ways, then the hard question is not about the truth in itself of any model, but the criteria for determining which of the (potentially infinite) models available we should choose in the first place. 

This question is not one for physics, but metaphysics. It necessarily exists outside any given model (© Paul Feyerabend). Here we meet our old friend, Occam's Razor. This isn't a scientific principle at all, but a pragmatic rule of thumb with no intellectual pedigree: all else being equal, take the simplest explanation. Occam's Razor is a favourite instrument for the torture of hapless Christians by grumpy biologists: all your tricksy afterlife wagers and so on fail because evolution is so much less complicated and has so much more explanatory value than the idea that an omniscient, intangible, invisible, omnipotent entity pulling strings we can't see to make the whole thing go.

But, alas, in seeking a grand unification of things that really aren't asking to be unified, cosmology reveals some almighty snags. Unification under Hawking's programme, if it is even possible, involves slaughtering some big old sacred cows. To name a few: causality, the conventional conception of space-time; the idea that scientific theories should be based on observable data and their outcomes testable. It bows to some truly heinous false idols too. For example: seven invisible space-time dimensions, a huge mass of invisible dark matter, an arbitrary cosmological constant, a potentially infinite array of unobservable universes which wink in and out of existence courtesy of a mathematically inferred "vacuum energy"). Hawking doesn't propose solutions to these problems, but seems to think they're a fair price for achieving grand unification.

I'm not so sure: other than intellectual bragging rights, the resulting unified theory has no obvious marginal utility. And it has political drawbacks: believing one's model to be the truth carries potentially unpleasant implications for the suppression of those who don't.

There are practical drawbacks, too. We are asked to reject existing theories, which still have quite a lot of utility, in favour of something that it infinitely harder to understand and work with. The accelerating expansion of the universe without any apparent acting force seems to violate Newton's second law of motion. Without an outrageous end-run, the first nanosecond of the Big Bang (wherein the universe is obliged to expand in size by ten squillion kilometres - i.e. far faster than the speed of light) seems to violate the fundamentals of general relativity. String theory requires seven necessarily unobservable space-time dimensions and/or entirely different universes, and even then doesn't yield a single theory but millions of the blighters, all slightly inconsistent with each other (hence the appeal to "model dependent reality).

From the camp which wielded Occam's Razor so heartily against the Christians, this seems a bit rich. If these are the options, then the razor might slice in favour of the big guy with the beard.

But these aren't the options. We could save a lot of angst, and perhaps could have avoided digging trillion dollar circular tunnel under Geneva, had we employed model dependent reality the way the philosophers saw it and not the scientists (and shouldn't we call a spade a spade and label it cognitive relativism, by the way?). Since it crossed the event horizon of observability modern cosmology has become arcane, stunt-mathematics. If there were a chance that it might deliver time-travel, hyperspace or a tool for locating wormholes to other galaxies or universes then one could see the point in this intellectual onanism. But none of that seems to be allowed. So we should therefore ask the question "but why? What's the point? What progress do you promise that we can't achieve some other way?" No one seems to be able to answer that question.

But if we park it, what's left of Stephen Hawking's latest book is some pretty ropey jokes.

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