The accidents are characteristic of the system itself

Laurence Gonzales in Deep Survival. Page 102.

Perrow's Normal Accidents, first published in 1984, is a work of seminal importance because of its unusual thesis: That in certain kinds of systems, large accidents, though rare, are both inevitable and normal. The accidents are characteristic of the system itself, he says. His book was even more controversial because he found that efforts to make those systems safer, especially by technological means, made the system more complex and therefore more prone to accidents.

In system accidents, unexpected interactions of forces and components arise naturally out of the complexity of the system. Such accidents are made up of conditions, judgments and acts or events that would be inconsequential by themselves. Unless they are coupled in just the right way and with just the right timing, they pass unnoticed. . . . Perrow's point is that, most of the time, nothing serious happens, which makes it more difficult for the operators of the system (climbers, in this case). They begin to believe that the orderly behavior they see is the only possible state of the system. Then at the critical boundaries in time and space, the components and forces interact in unexpected ways, with catastrophic results.