The purpose of this book is to explore the human contribution to both the reliability and resilience of complex well-defended systems. The predominant mode of treating this topic is to consider the human as a hazard, a system component whose unsafe acts are implicated in the majority of catastrophic breakdowns. But there is another perspective, one that has been relatively little studied in its own right, and that is the human as hero, a system element whose adaptations and compensations have brought troubled systems back from the brink of disaster on a significant number of occasions. What, if anything, did these heroes have in common? Can these abilities be 'bottled' and passed on to others?Insightful, eloquent and extremely accessible, James Reason provides the reader with an essential guide to human behaviour on individual and organisational levels, examining the human from both perspectives.