Book excerpt: For Resilience Engineering, 'failure' is the result of the adaptations necessary to cope with the complexity of the real world, rather than a malfunction. Human performance must continually adjust to current conditions and, because resources and time are finite, such adjustments are always approximate. Featuring contributions from leading international figures in human factors and safety, Resilience Engineering provides thought-provoking insights into system safety as an aggregate of its various components - subsystems, software, organizations, human behaviours - and the way in which they interact.