One single observation can invalidate a general statement derived from millennia of confirmatory sightings of millions of white swans. All you need is one single (and, I am told, quite ugly) black bird.
Nicholas Nassim Taleb, The Black Swan - prologue, paragraph 1
The association of "ugly" with black swan primes readers to spend the rest of the book in fear of the rhetorically imbued negative implications of not knowing an outcome with certainty. No thanks.
Unknowing is the heart of possibility. Unknowing is a source of adventure. Unknowing is infinity - certainty, zero.