It's a great parable, told by Sam Spade in Dashiell Hammett's The Maltese Falcon. On the way to lunch, a real estate man named Flitcraft is almost killed by a beam falling from a high floor of a building under construction. A chip thrown up from the sidewalk leaves a scar on his cheek.
By the end of lunch, Flitcraft decides to simply walk out of his comfortable, middle-class life in Tacoma - and vanishes, walking out on his family, his job and his savings without a goodbye to anyone.
Sam Spade explains, "He knew then that men died at haphazard like that, and lived only while blind chance spared them. It was not, primarily, the injustice of it that disturbed him: he accepted that after the first shock. What disturbed him was the discovery that in sensibly ordering his affairs he had got out of step, and not in step, with life."
A close encounter with death, and awareness of the role of the "haphazard", changes people, that's for sure. Ironically, when spotted years after his vanishing act, Flitcraft has settled into a life very similar to the one he abandoned, with a similar wife and car, and the same date with the golf course at four every afternoon.
In his brilliant novel Oracle Night, Paul Auster tells the story of a novelist who accepts the challenge to write a new version of the Flitcraft parable.