This chapter examines ideas of varying levels of generality that define how policymakers should act. Building upon and drawing together the best work in the field, it seeks to offer a synthetic analysis of how ideas matter in politics: what is known, what is not known, and what areas are in need of further research. It considers ideas at three levels of generality: policy solutions, problem definitions, and public philosophies or zeitgeist. It also consider interactions between the levels of ideas, with a particular interest in “upward-flowing” interactions, showing that not only does the conception of a problem constrain policy alternatives, but the fate of specific policy solutions also can have an impact on problem definitions or even broader public philosophies.
