 This work, written by the fathers of post-normal science, discusses the use of science for policy and its problems.The book emphasizes the need for craft skills with numbers – not only in statistics but also in cost-benefit analysis, and on the need of specific skills for policy-related research.It introduces for the first time NUSAP, a new notational system for the management of uncertainty and quality in quantitative information, and presents examples of its application to radiological hazards, the valuation of ecosystems, and to energy technologies.