It is no coincidence that we speak of “a climate of trust,” for the health of a society depends on trust much as the health of a region depends on the weather. Just as thousands of subtle interacting factors determine the quality of the natural climate, so thousands of small individual behaviours determine the quality of the social climate. Chaos theory posits that a butterfly fluttering its wings in one part of the world can set off a hurricane in another. Just so, a random act of indifference toward another human being may contribute to the degradation of the social climate.