Just a Gwai Lo

Richard Posner: “There is an old but still useful distinction between "risk" and "uncertainty," the former referring to contingencies to which a probability can be attached, the latter to contingencies to which no probability can be attached. The former is the domain of insurance and cost-benefit analysis. The latter? No one can assign a probability to any given time, place, or manner of a terrorist attack within a very broad range (obviously some possibilities can be excluded); and yet we have to take counterrorist measures; we have, in short, to manage uncertainty as well as risk.”