Global Guerrillas: WAS 9/11 A BLACK SWAN?:
“Nassim Taleb, a scientist-philosopher-businessman, makes the case that 9/11 was a black swan. A black swan is a unpredictable event that defies prediction. An outlier. I agree. He expands:
A vicious black swan has an additional elusive property: its very unexpectedness helps create the conditions for it to occur. Had a terrorist attack been a conceivable risk on Sept. 10, 2001, it would likely not have happened.
link via Warren Ellis.