Niall Ferguson in The Telegraph:
It was predictable. Cho Seung-Hui was a taciturn, moody loner. Four of his professors expressed concerns about the content of his work or classroom conduct. After complaints by two female students, the campus police and a college counsellor tried to have him committed to a mental institution. But a doctor didn’t agree with the judge that he presented a danger to others. And guns are easy to buy in America (though banned on Virginia campuses). As a result 33 people are dead.
Journalists’ efforts to explain the Virginia Tech massacre perfectly illustrate one of the central points of an idiosyncratically brilliant new book by Nassim Nicholas Taleb, The Black Swan: The Impact of the Highly Improbable (Penguin/Allen Lane). Having been completely caught out by some random event, we human beings are wonderfully good at retrospectively predicting it. In reality, however, Cho was what Taleb calls a “Black Swan”.
Why a black swan? Taleb’s starting point is what philosophers call the problem of induction. Suppose you have spent all your life in the northern hemisphere and have only ever seen white swans. You might very well conclude (inductively) that all swans are white. But take a trip to Australia, where swans are black, and your theory will collapse. A “Black Swan” is therefore anything that seems to us, on the basis of our limited experience, to be impossible.
More here.