Welcome to the fascinating and turbulent world of international politics. Wars, the decisive influence of multinational companies, the migrant crisis, pandemics, climate change: it would be an understatement to say that the impact of international issues on our societies is very direct, if not, more bluntly, on human life itself. All these issues are embedded in what is commonly known as the theories of International Relations (IR). Like any other phenomenon in political and social life, international relations is an object of study that needs to be theorised in order to be grasped through in-depth, well informed and wise knowledge. Consciously or unconsciously, academically or not, our interpretations of the international politics are often linked to existing theoretical approaches (realism, idealism, Marxism, constructivism, etc.) which emphasise various causal factors such as national interests, the role of non-state actors, anarchy, the importance of cooperation, the economy or ideas and norms. The central aim of this course is to give an account of the main theories of the international system, their postulates, their analytical capacities, their explanatory power and their limits.