This chapter is about reflections on several approaches to International Relations theory given the case studies and the findings of this book. It is not the aim of this chapter to conduct a full review of theory but rather to comment on theories and ideas in International Relations given the lessons learned from the complex web of human relations in the three river systems. In general, no theory can be said to have provided a perfect fit but some approaches, including Classical Realism and Social Constructivism, seem to be more promising than others.