In the course of a long professional life spent, or misspent, in the study of the strengths of materials and structures, I have had cause to examine a lot of accidents, many of them fatal. I have been forced to the conclusion that very few accidents just "happen" in a morally neutral way. Nine out of ten accidents are caused, not by more or less abstruse technical effects, but by old-fashioned human sin — often verging on plain wickedness. Of course I do not mean the more gilded and juicy sins like deliberate murder, large-scale fraud, or Sex. It is squalid sins like carelessness, idleness, won't-learn-and-don't-need-to-ask, you-can't-tell-me-anything-about-my-job, pride, jealousy and greed that kill people.