LOOK at the complex world around you. There's a basic assumption that the things you see – be it humans, computers or trees – can ultimately be boiled down to the behaviour of the particles they are composed of. Biology is determined by chemistry, which is in turn governed by the underlying physics. Much of modern science is rooted in this bottom-up, reductionist view of cause and effect, which has been an excellent way of explaining many phenomena. But can all things be understood just by looking at their constituent parts?
Consider a computer. You want to type a document, so you press the keys to give the sequence of letters "I love this machine because it is so obedient". Electrons in the transistors in the central processing unit obligingly flow in such a way as to make these letters appear on the screen. The underlying physics – governed by ...
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