The concept of "identity" has gained increasing currency in international relations scholarship, but it offers too many vague and imprecise definitions of the concepts that stand at its very core. Most of this scholarship does not go beyond the mere assertion that identity is important and that somehow, in one way or another, it plays a role in how many states define and pursue their national interests. As a consequence many scholars have argued that the identity school had little to offer, and that norms and institutions offered explanations similar to those drawn from identity. This text offers clear definitions of the concept of identity and the concepts surrounding the term, and aims to demonstrate the causal link between identity and the behaviour of states.