This chapter explicates the theoretical and conceptual framework of the book. It embeds the adopted discursive-ideational approach to policy analysis within broader theoretical debates on the nature of human motivation and institutional change. In particular, it defines the three key concepts of the framework—ideas, discourse, and power—and identifies causal mechanisms associated with different types of ideational power. It also conceptualises the interactive discourses on the creation of the EPPO with reference to the main institutional arenas where the EPPO was debated. Finally, the chapter theorises the substantive content of discourses on the EPPO based on the discursive institutionalist conceptualisation of discourse as containing both necessity-based (cognitive) and value-based (normative) ideas.