“Black Swan” is a term I probably need to explain before I proceed. There used to be a saying in Medieval England that something was about as likely as “finding a Black Swan”, meaning it was highly unlikely, akin to “when pigs fly”. According to historical record, this term was in widespread use until the 17th Century and the discovery of Australia, which bought with it the first sighting of a Black Swan in 1697. In scientific terms this is known as a paradigm shift, it was a discovery that couldn’t be incorporated into the current understanding, it had to redefine it. And clearly, the metaphor could no longer be used.
Nassib Taleb, in his book of the same name, defines the Black Swan as an event which is 1) hard to predict, 2) highly consequential, and 3) wrongly retro-predicted. The history of human culture is a progression of these Black Swans: the internet, the home computer, the motor car, wikipedia, Harry Potter, Princess Diana, facebook, the Renaissance. World War I was a Black Swan, it may look predictable in hindsight, but prior to it actually happening it was near unimaginable.
zdroj:
http://zenbullets.com/blog/?p=160