Today was a most productive day: I disproved the old theory that “all swans are white.” In the words of Karl Popper, “No number of sightings of white swans can prove the theory that all swans are white. The sighting of just one black one may disprove it.”
Swans, white and black, birds of the genus cygnus, have figured prominently in the thought of philosophers for over two thousand years. Aristotle was, I suppose, the first to use the ‘white swan’ as an example of inductive reasoning, though I always found his book Prior Analytics a little to0 dense for easy comprehension. But from the time of Aristotle and certainly from the time of Juvenal (the Roman poet who lived in the second century AD), the notion that there might be swans that are actually black was considered a very funny idea, as when Juvenal said: “a good person is as rare as a black swan”.
Popper, on the other hand, was using the swan to establish his belief that it is the job of the scientist to disprove theories not to prove them, thus he arrived at his ‘theory of falsifiability’. Alas, after my little walk to see the black swan, I arrived at no new theories - but arrived only at the little B&B where we are staying on the lake shore.