Karl Popper and the black swan

The philosopher Sir Karl R. Popper (1902-1994) made an important contribution to the philosophy of science. He showed that we can refute empirical hypotheses, but not prove them. A famous example concerns the hypothesis "All swans are white.". Even if we don't find a black swan among 10,000 swans, we can never be sure that there is no black swan in the world. Popper's (quite more complex) theory has led to research designs being more thorough today than they were 80 years ago.