This chapter introduces the concept of international relations (IR) theory. It highlights the importance of the historical context in understanding the different theories of international relations that have emerged over the years and why they fall in and out of favour. New theoretical perspectives are constantly coming to the fore and they tend to develop as a result of intellectual reasoning. However, quite often there will be practical consequences of implementing such intellectually grounded theories. The chapter then explores the interplay between international relations, international politics, and world politics and looks at the key concepts of ontology, epistemology, and methodology. It then provides an outline of a number of IR theories, such as liberalism and realism, before acknowledging that there is no right or best IR theory and it is important to keep an open mind.
