Tuesday, 4 January 2011

The Fabric of Reality

by David Deutsch

This is a frustrating book, I feel that there is some good stuff in there, but that the arguments aren’t that well made.

Deutsch’s theme seems to be that we can construct a theory of everything from four current scientific theories; the Turing Principle of a universal computer, the multiverse version of quantum physics, Karl Popper’s view of knowledge and Dawkin’s update of Darwininan evolution, and the greatest of these is quantum theory. The argument is that all these theories can be related, and that as quantum theory is the most basic -in terms of physics and mathematical description- then it is the most important. The other three theories are emergent, that is they can’t be connected directly, mathematically, to the base theory, in the way that say large parts of chemistry can be, yet they still provide good working explanations of the universe (multiverse!) as it is.

That word explanation is key to the book, he explains (following Popper) that all scientific theories are explanations of problems that we use until we find a better one. I struggled with the word problem, but if I read it more as a conundrum, or define it as something that needs an explanation it helps. An explanation is deemed to be good if it is the simplest one to fit all the known facts, reference William of Occam. So whilst we can describe planetary motion in terms of angels moving heavenly bodies about the earth so as to appear that the earth rotates about the sun, it’s much simpler just to treat the earth as moving around the sun -which we would have to, angels or no- than to worry about the motives of the angels as well.

It is also central to the book that we should treat explanations as serious and true until we find a problem with them that needs a new explanation. So Newtonian mechanics was believed in, and treated as true and the world advanced using Newton for two or three centuries until problems arose (such as the orbit of Mercury being slightly different to that predicted) that required a new explanation. That explanation was General Relativity. Deutsch argues that this is not the case with his chosen theories, although they are the best explanations that we currently have they are not taken seriously, at least in part because we just don’t like them. Quantum theory is downright weird. You either have to believe in the Copenhagen Interpretation that the world changes because you look at it; or the multiverse theory where new universes are created at every decision point, that damn cat is dead and alive. The Selfish Gene is a cold and amoral theory and doesn’t need a god. Not a worry when you’re talking about rocks and atoms, but this is personal and we have emotional problems dealing with it. The Turing principle is fine -but largely ignored, we’re too busy playing with computers to think much about them and perhaps the same is true of Popper, although it seems pretty similar to the scientific method as I was taught it in school.

So what do I think? It’s not very coherent -perhaps because three of the theories are emergent so we can’t formally tie everything together. There are links there between the theories, obvious ones between Turing and Dawkins, and computers are, in a limited sense, quantum devices anyway. So worth reading, lots to think about, but for me it lacked a defined central argument and some of the logic chopping seemed to get close to the ‘All elephants are grey, the battleship is grey, therefore the battleship is an elephant.’; although I do realise that this is because we are supposed to assume the four theories to be absolutely true and dream up ideas around that assumption, ideas that we can then test.

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