pWhy do giraffes have long necks It can't really be for reaching tasty leaves since their main food is ground level bushes, tidy though that explanation would be. And how does relativity theory cope with the fact that the observable universe defies prediction by being far too small and anything but homogeneous By inventing a vastly larger, but invisible, universe. And what exactly should we make of the scientists who claim to be witnessing thought itself, when the changes of blood flow in the brain that they observe are a thousand times slower than the neuronal activity it is supposed to reveal A little scepticism is in order.ppYet if philosophers of science, from Thomas Kuhn to Paul Feyerabend, have argued that science is a more haphazard process, driven by political fashion and short-term economic self-interest, today almost everyone seems to assume it is a vast jigsaw of interlocking facts pieced slowly but steadily together by expert practitioners.ppIn this witty but profound 21st-