Going to war is like walking off a very long cliff: at any point you can decide to turn around and walk the other way; you can stop walking altogether, you can decide at the edge not to jump afterall, and once you've jumped you can usually grab a root or a ledge and pull yourself back up. It is only by deciding again and again with each footstep that you will not choose another course of action that a full-scale disaster happens. It doesn't happen by chance.

This is a paraphrase of a metaphor I first encountered in the book Use of Weapons, a novel by Iain Banks, but I've since heard it expressed elsewhere. It seems to me that it applies to many preventable tragedies: everything from global warming to the breakup of a marriage or the development of heart disease.

Once in a while I encounter a metaphor that helps me to see things much more clearly. This is one of them.