This chapter examines constructivist approaches to international relations theory. It explores whether there is a possibility of moral progress in world politics, whether some cultures and countries are more (or less) inherently violent, and whether states are motivated by power or by ideas. The chapter also discusses the rise of constructivism and some key concepts of constructivism, including the agent–structure problem, holism, idealism, individualism, materialism, and rational choice. It concludes with an analysis of constructivist assumptions about global change. Two case studies are presented, one relating to social construction of refugees and the 2015 European migration crisis, and the other to the ‘human rights revolution’ and torture. There is also an Opposing Opinions box that asks whether the laws of war have made war less horrific.