I don’t particularly care about the usual. If you want to get an idea of a friend’s temperament, ethics, and personal elegance, you need to look at him under the tests of severe circumstances, not under the regular rosy glow of daily life. Can you assess the danger a criminal poses by examining only what he does on an ordinary day? Can we understand health without considering wild diseases and epidemics? Indeed the normal is often irrelevant.

Nassim Nicholas Taleb (b. 1960) Lebanese-American essayist, statistician, risk analyst, aphorist

The Black Swan, Introduction (2007)
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