Great intellectual effort has gone into the development of sophisticated designs and methodologies to study individual policies, programs, and projects. Costly efforts to find the smallest evidence of a policy or program impact have been undertaken in the presumption that such data are central to policy decision making. Meanwhile, the intergovernmental nature of political and policy governance has been ignored. Whether it is Canada, the United States, England, Denmark, Sweden, Germany, Japan, or any other industrial country, the governmental structure is essentially a web of interrelated...

Knowledge grows as ideas are tested against each other. Agreement is not resolved simply by naming concepts, but in the dialectical process of thesis, antithesis, and synthesis. There are many echoes of these debates in The Evidence Book. The contributors make claims for both practitioner wisdom and the voice of experience. Against this is posed the authority of experimental science and the randomized controlled trial. The contributors are concerned, in their own ways, with collecting, ranking, and analyzing evidence and using this to deliver evaluations. As an expert group, they are aware...