Nassim Nicholas Taleb defines black swans as events that:
- Are totally unpredictable by mortal minds.
- Have a disproportionately large impact.
- Have retroactive predictability imposed on them through the foresight of 20/20 hindsight.
Taleb frequently points to the outbreak of World War I as an example of a black swan. He scoffs at historical accounts that present the outbreak as the result of trends that built up over the preceding decades, dismissing them as manifestations of the narrative fallacy:
Narrative fallacy: our need to fit a story or pattern to a series of connected or disconnected facts.
As evidence of the narrative fallacy in histories of World War I, Taleb cites Niall Ferguson’s The Pity Of War
…historians arrive on the scene. They are the scholars who specialize in the study of “fat tail” events—the low-frequency, high-impact moments that inhabit the tails of probability distributions, such as wars, revolutions, financial crashes, and imperial collapses. But historians often misunderstand complexity in decoding these events. They are trained to explain calamity in terms of long-term causes, often dating back decades. This is what Nassim Taleb rightly condemned in The Black Swan as “the narrative fallacy”: the construction of psychologically satisfying stories on the principle of post hoc, ergo propter hoc.
Drawing casual inferences about causation is an age-old habit. Take World War I. A huge war breaks out in the summer of 1914, to the great surprise of nearly everyone. Before long, historians have devised a story line commensurate with the disaster: a treaty governing the neutrality of Belgium that was signed in 1839, the waning of Ottoman power in the Balkans dating back to the 1870s, and malevolent Germans and the navy they began building in 1897. A contemporary version of this fallacy traces the 9/11 attacks back to the Egyptian government’s 1966 execution of Sayyid Qutb, the Islamist writer who inspired the Muslim Brotherhood. Most recently, the financial crisis that began in 2007 has been attributed to measures of financial deregulation taken in the United States in the 1980s.
Ferguson proclaims that the real truth is found in the opposite direction:
In reality, the proximate triggers of a crisis are often sufficient to explain the sudden shift from a good equilibrium to a bad mess. Thus, World War I was actually caused by a series of diplomatic miscalculations in the summer of 1914, the real origins of 9/11 lie in the politics of Saudi Arabia in the 1990s, and the financial crisis was principally due to errors in monetary policy by the U.S. Federal Reserve and to China’s rapid accumulation of dollar reserves after 2001. Most of the fat-tail phenomena that historians study are not the climaxes of prolonged and deterministic story lines; instead, they represent perturbations, and sometimes the complete breakdowns, of complex systems.
I’m going to quibble with the Laurence A. Tisch Professor of History here.
