Knowledge, power, and participation are absolutely central to the understanding of any policy. But it is the area of environmental policy issues where, from the 1970s onwards, an impressive knowledge base has become available across various disciplines and research traditions. The process of rethinking scientific and political rationality is evident in developments within converging fields such as political science, including international relations, public administration and implementation studies; the utilization of knowledge tradition in the policy sciences; the sociology of science and technology; technology and integrated environmental assessment; and philosophy of science. The study of environmental policy issues tends to bring about a convergence between research areas in political science that have stood apart for most of the twentieth century. The implications for political theory have drawn attention especially since the nuclear power issue provoked a flow of publications in the 1980s. The chapter also presents an overview of the key concepts discussed in this book.