International relations is a broad and ever-expanding field, covering all sorts of social practices that cross borders. This discussion will provide an in-depth introduction to a number of topics. To begin, though, it is important to lay out the major analytical approaches that have come to define the discipline of international relations. One of the earliest lessons within the discipline was that the way one looks at things, the theoretical lens one employs to analyse phenomena, determines much of what one sees. The world is a complex place, and it is impossible to understand and discuss it is in its totality -- any analysis necessarily requires some sort of simplification and abstraction to make sense of things. Theories are one way to do this, each privileging certain things.