Sustainable development, albeit a fashionable phrase, covers several substantive issues. In essence, as the Bruntlandt Report has it, it is "development that meets the needs of the present without compromising the ability of future generations to meet their own needs". Underlying this concern is the issue of modelling and evaluating alternative long-term dynamic paths open to an economy which, in an essential way, is dependent on environmental inputs. section one of this book presents two non-technical surveys of some of the questions in the areas of dynamics and uncertainty. The papers in section two then go on to model and evaluate alternative development paths of an economic - environmental system, especially with reference to their long-run properties. Of course, many of the processes and relationships underlying such models are uncertain, and the types of uncertainty and how to model them are considered in section three. There are many complex and interesting economic issues that arise when we consider how best to manage the "global commons" as privately produced public goods, and the present book deals with many of the related issues in an informative way.