A Little History of Philosophy (Little Histories)

by Nigel Warburton

Scientists then find a way of testing this hypothesis – in this case, getting a lot of different sorts of gas and heating them. But ‘testing’ doesn't mean finding evidence to support the hypothesis; it means trying to prove that the hypothesis can survive attempts to falsify it. Ideally the scientists will look for a gas that doesn't fit the hypothesis. Remember that in the case of the swans it only took one black swan to undermine the generalization that all swans are white. Similarly, it would only take one gas that failed to expand when heated to undermine the hypothesis that ‘All gases expand when heated.’ If a scientist refutes a hypothesis – that is, shows that it is false – then that results in a new bit of knowledge: the knowledge that the hypothesis is false. Humanity progresses because we learn something. Observing lots of gases which do expand when heated won't give us knowledge, except perhaps a little more confidence in our hypothesis. But a counter-example really teaches us something. For Popper a key feature of any hypothesis is that it has to be falsifiable. He used this idea to explain the difference between science and what he called ‘pseudo-science’. A scientific hypothesis is one that can be proved wrong: it makes predictions that can be shown to be false.