Book excerpt: Debate over the important concept of externality has influenced our perception of the role of governing authorities and has become central to our appraisal of the ecology-economy connection. Despite this, it remains hazy as a concept. This book examines ideas of externality and some of the ways that these have influenced and should continue to influence economics. The difficult issue of defining or characterising externalities is tackled and the effect that externality theory has had on major economic issues is investigated. The author provides a distinctive and non-technical survey of the various methodological approaches taken by economists to the issue of externalities. He fully explains and analyses the ideas lying behind the theory and looks at the failure of some markets to reconcile individual and social costs and benefits. The book's major theme is an exploration of institutional inefficiency and the implications of incorporating organizational costs into economic models.