The Science of Discworld II

his day, when chemists had already moved on. Archimedes doesn’t seem to have followed the scientific method, possibly because he was clever enough not to need it.
    The textbook scientific method combines two types of activity. One is experiment (or observation – you can’t experiment on the Big Bang but you can hope to observe traces that it left). These provide the reality-check that is needed to stop human beings believing something because they want it to be true, or because some overriding authority tells them that it’s true. However, there is no point in having a reality-check if it’s bound to work, so it can’t just be the same observations that you started from. Instead, you need some kind of story in your mind.
    That story is usually dignified by the word ‘hypothesis’, but less formally it is the theory that you are trying to test. And you need a way to test it without cheating. The most effective protection against cheating is to say in advance what results you expect to get whenyou do a new experiment or make a new observation. This is ‘prediction’, but it may be about something that has already happened but not yet been observed. ‘If you look at red giant stars in this new way then you will find that a billion years ago they used to …’ is a prediction in this sense.
    The most naïve description of the scientific method is that you start with a theory and test it by experiment. This presents the method as a single-step process, but nothing could be further from the truth. The real scientific method is a recursive interaction between theory and experiment, a complicity in which each modifies the other many times, depending on what the reality-checks indicate along the way.
    A scientific investigation probably starts with some chance observation. The scientist thinks about this and asks herself ‘why did that happen?’ Or it may be a nagging feeling that the conventional wisdom has holes in it. Either way, she then formulates a theory. Then she (or more likely, a specialist colleague) tests that theory by finding some other circumstance in which it might apply, and working out what behaviour it predicts. In other words, the scientist designs an experiment to test the theory.
    You might imagine that what she should be trying to do here is to design an experiment that will prove her theory is correct. 4 However, that’s not good science. Good science consists of designing an experiment that will demonstrate that a theory is wrong – if it is. So a large part of the scientist’s job is not ‘establishing truths’, it is trying to shoot down the scientist’s own ideas. And those of other scientists. This is what we meant when we said that science tries to protect us against believing what we want to be true, or what authority tells us is true. It doesn’t always succeed, but that at least is the aim.
    This is the main feature that distinguishes science from ideologies, religions and other belief systems. Religious people often get upset when scientists criticise some aspect of their beliefs. What they fail to appreciate is that scientists are equally critical about their own ideas and those of other scientists. Religions, in contrast, nearly always criticise everything except themselves. Buddhism is a notable exception: it emphasises the need to question everything. But that may be going too far to be helpful.
    Of course, no real scientist actually follows the textbook scientific method unerringly. Scientists are human beings, and their actions are driven to some extent by their own prejudices. The scientific method is the best one that humanity has yet devised for attempting to overcome those prejudices. That doesn’t mean that it always succeeds. People, after all, are people.
    The closest that Hex manages to come to genuine science is Phocian the Touched’s lengthy and meticulous investigation of Antigonus’s theory of the trotting horse. We hope that you have heard of neither of these gentlemen, since, to the best of our knowledge, they never existed. But then, neither did the Crab Civilisation – which didn’t stop the crabs making their Great Leap Sideways. Our story here is modelled on real events, but we’ve simplified various otherwise distracting issues. With which we shall now distract you.
    The prototype for Antigonus is the Greek philosopher Aristotle, a very great man who was