“If you wish to upset the law that all crows are black, you mustn't seek to show that no crows are; it is enough if you prove one single crow to be white.”

“In order to disprove the assertion that all crows are black, one white crow is sufficient.”

“The crow wished everything was black, the Owl, that everything was white.”

“And although I have seen nothing but black crows in my life, it doesn't mean that there's no such thing as a white crow. Both for a philosopher and for a scientist it can be important not to reject the possibility of finding a white crow. You might almost say that hunting for 'the white crow' is science's principal task.”

“The crows assert that a single crow could destroy the heavens. This is certainly true, but it proves nothing against the heavens, because heaven means precisely: the impossibility of crows.”

“I will make thee think thy swan a crow.”

“Both for a philosopher and for a scientist it can be important not to reject the possibility of finding a white crow. You might almost say that hunting for 'the white crow' is science's principal task”