Before the discovery of Australia, people in the Old World were convinced that all swans were white, an unassailable belief as it seemed completely confirmed by empirical evidence.
The sighting of the first black swan might have been an interesting surprise for a few ornithologists (and others extremely concerned with the coloring of birds), but that is not where the significance of the story lies.
It illustrates a severe limitation to our learning from observations or experience and the fragility of our know- ledge.
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.
I push one step beyond this philosophical-logical question into an empirical reality, and one that has obsessed me since childhood.
What we call here a Black Swan (and capitalize it) is an event with the following three attributes.
First, it is an outlier, as it lies outside the realm of regular expectations, because nothing in the past can convincingly point to its possibility.
Second, it carries an extreme impact (unlike the birds).
Third, in spite of its outlier status, human nature makes us concoct explanations for its occurrence after the fact, making it explainable and predictable.
I stop and summarize the triplet: rarity, extreme impact, and retrospective (though not prospective) predictability.
A small number of Black Swans explain almost everything in our world, from the success of ideas and religions, to the dynamics of historical events, to elements of our own personal lives.
Ever since we left the Pleistocene, some ten millennia ago, the effect of these Black Swans has been increasing.
It started accelerating during the industrial revolution, as the world started getting more complicated, while ordinary events, the ones we study and discuss and try to predict from reading the newspapers, have become increasingly inconsequential.
Just imagine how little your understanding of the world on the eve of the events of 1914 would have helped you guess what was to happen next.
(Don’t cheat by using the explanations drilled into your cranium by your dull high school teacher.) How about the rise of Hitler and the subsequent war?
How about the precipitous demise of the Soviet bloc?
How about the rise of Islamic fundamentalism?
How about the spread of the Internet?
How about the market crash of 1987 (and the more unexpected recovery)?
Fads, epidemics, fashion, ideas, the emergence of art genres and schools.
All follow these Black Swan dynamics.
Literally, just about everything of significance around you might qualify.