This volume is the result of a collective effort made by its authors to reason and write about environmental policy from an empirical, rather than from a prescriptive perspective. Since the authors, like most people, care about the environment and, as professional economists or political scientists, have some expertise to offer in the area of policy-design, it was not always easy for them to keep on the intended track. Whereas they knew that it is unusual to follow a strictly empirical approach in such a 'practical' field as environmental policy, they discovered only during the effort what kind of difficulties would be encountered. Moreover, they learned that it is sometimes necessary to reason normatively in order to catch essential features of empirical reality. As it turns out, moral notions cannot entirely be neglected in political life. The predominance of homo economicus is not absolute. We feel that the effort has been worthwile and deserves to be repeated and expanded. It has been a truly co-operative project and we are very grateful to all authors for their willingness to contribute. Special gratitude we owe to Frans van Nispen and Annemarie Rima. Frans van Nispen has assisted us in every conceivable way during the preparation of this book.