War is unique, but the same point holds in other contexts, including the domain of climate change, in which costly precautions inevitably create risks. This is not to say that we should not take action to avert the dangers posed by climate change; we should. But if we take steps to reduce risks, we will always create fresh hazards. No choice is risk-free. For environmental and other problems, we need to decide which risks to combat - not comfort ourselves with the pretense that there is such a thing as a "safe" choice.

The nations of the world should take precautions, certainly. But they should not adopt the precautionary principle.