Weak and strong conditions for sustainable development : clarification of concepts and their policy application.

As is well known there are a variety of concepts of sustainable development. This paper concentrates on the main economic concept of sustainable development and discusses weak and strong conditions for it, taking into account the scope for substituting different types of capital - man-made capital (physical and human) and natural resource or environmental capital. A simple diagrammatic approach is adopted which should help to clarify controversies in this area, and allow also for the views of ecocentric persons. The possibility is explored that the conditions for sustainable development may differ between countries - some are able to adopt weaker conditions than others. In addition, some of the implications of weak and strong sustainability for project evaluation are explored and a dilemma is raised about offset policies as a means for satisfying strong sustainability conditions