How do we imagine the worst that can happen? What happens when our leaders fail to imagine worst cases? Why is disaster sometimes good for society? Why should we do more worst case thinking? These are the central questions that I answer in Worst Cases. The usual view about danger and catastrophe is that it's irrational to worry about low probability events: airplane crashes and nuclear power meltdowns are good examples. That's probabilistic thinking and in modern times it is equated with reason itself. Worst case thinking is different. It emphasizes consequences over probabilities: what if terrorists commandeer four airplanes simultaneously, what happens if the power-grid goes down for six months, how many might die if a chemical plant explodes? Conceptions of "the worst" permit exploration of how culture and society shape the imagination. Designations of the worst involve both prospective and retrospective viewpoints. As such they tell us about people's orientations toward the past and the future, as well as toward self, others, and society. Disasters, even worst cases, are normal parts of life. They are prosaic. The rules that govern social life in non-disastrous situations are reproduced in disastrous ones, because disasters are not special. We can lead safer and more interesting lives by coming to grips with living and dying in a worst case world.

http://worstcases.com. Excerpted in The Guardian: http://www.guardian.co.uk/science/story/0,3605,1637497,00.html