The tension between professional expertise and democratic governance has become increasingly significant in Western politics. Environmental politics in particular is a hotbed for citizens who actively challenge the imposition of expert theories that ignore forms of local knowledge that can help to relate technical facts to social values. Where information ideologues see the modern increase in information as capable of making everyone smarter, others see the emergence of a society divided between those with and those without knowledge. Suggesting realistic strategies to bridge this divide, Fischer calls for meaningful nonexpert involvement in policymaking and shows how the deliberations of ordinary citizens can help solve complex social and environmental problems by contributing local contextual knowledge to the professionals’ expertise. While incorporating theoretical critiques of positivism and methodology, he also offers hard evidence to demonstrate that the ordinary citizen is capable of a great deal more participation than is generally recognized. Popular epidemiology in the United States, the Danish consensus conference, and participatory resource mapping in India serve as examples of the type of inquiry he proposes, showing how the local knowledge of citizens is invaluable to policy formation. In his conclusion Fischer examines the implications of the approach for participatory democracy and the democratization of contemporary deliberative structures. This study will interest political scientists, public policy practitioners, sociologists, scientists, environmentalists, political activists, urban planners, and public administrators along with those interested in understanding the relationship between democracy and science in a modern technological society.