Our lives increasingly take place in ever more complex and interconnected networks that blur the boundaries we have traditionally used to define our social and political spaces. Accordingly, the policy problems that governments are called upon to deal with have become less clear-cut and far messier. This is particularly the case with climate change, environmental policy, transport, health and ageing - all areas in which the tried-and-tested linear policy solutions are increasingly inadequate or failing. What makes messy policy problems particularly uncomfortable for policy makers is that...