The Fukushima safety engineers were trying to prevent harm with their safety assessment, and they failed by ignoring an important but low-probability event. In just the same way, when trying to do good, we need to be sensitive both to the likelihood of success and to the value of that success. This means that low-probability, high-payoff activities can take priority over sure bets of more modest impact. It also shows that people are often confused when they say that ‘one person can’t make a difference’. Voting provides a vivid illustration.
