tl;dr: Richard Cook's classic essay argues that complex systems (healthcare, aviation, power) are inherently hazardous and always run in a degraded mode with latent failures; catastrophes require multiple small failures to align, not a single "root cause." Human operators are the adaptive element that continuously creates safety by gambling under uncertainty, though hindsight bias causes investigators to unfairly label their actions as errors after accidents. Safety is an emergent property of the whole system, not a component that can be added, and post-accident fixes often increase complexity and introduce new failure modes.