Concepts are a key feature of academic research and international politics. Despite the fact that interpreting, classifying and communicating the world through concepts has far-reaching social and political consequences, their various roles and complex dynamics remain poorly understood in International Relations (IR). Instead of disregarding concepts, conflating them with other cognitive terms such as norms, or obsessing about their ability to scientifically capture reality, this dissertation builds on the emerging field of critical concept studies (CSS), which understands concepts as open and contestable interpretive devices that observers use to make sense of the world, often to steer political thought and action. In line with CSS, this d...