When faced with a human error problem, you may be tempted to ask 'Why didn't they watch out better? How could they not have noticed?'. You think you can solve your human error problem by telling people to be more careful, by reprimanding the miscreants, by issuing a new rule or procedure. These are all expressions of 'The Bad Apple Theory', where you believe your system is basically safe if it were not for those few unreliable people in it. This old...