In this chapter, Robert Pinker discusses the complex relationship between social theory and social policy in democratic societies, focusing on the work of the philosophers Hilary Putnam and Karl Popper. Pinker first considers the distinction between scientific theory, normative theory and ideology and whether it is possible — or desirable — to design and implement rational social policies in the fractious world of democratic party politics. He then examines the interrelationships between policy making, policy research and public opinion and goes on to describe behavioural and structural models of poverty, as well as how poverty relates to liberal individualism, social inequality, socialism and collectivism. Pinker argues that the development and testing of theories is an essential element in the conduct of social research. He also comments on the work of Amartya Sen on the capability approach and its relevance to poverty analysis.