Incremental decisions in a complex world

Decision makers are used to complicated problems, those rich in detail. Whether they are trying to manage a computer or a farm, managers know how to get the task done-break it down into its constituent parts, get an expert to solve each part and stitch the whole together with a management hierarchy. This approach fails with complex problems, those rich in structure. What do you do when a decision in one area affects another? How do you decide to close an uneconomic railway service without understanding the impact on roads, housing or employment? These problems are the domain of system engineering, which seeks quantitative answers, not qualitative guessing; a description of the whole, not just the parts; answers that are good enough, not exact, and so offer the decision maker a rational basis for choice.