In international relations, a story from game theory called the prisoner's dilemma is often used to illustrate the decisions of two interacting actors under certain conditions. This prisoner's dilemma presupposes that captives, when faced with the option of cooperating with or squealing on one another, will always choose to squeal. This is the best option given the circumstances.

The realist perspective uses this example to illustrate what they see as basic truths – the international system is anarchic, forcing states to rely on self-help for protection. Because states exist in a security dilemma, they, like the prisoners, cannot trust one another enough to cooperate.

The liberal perspective, in contrast, believe that repeated interactions, changes in technology, and institutions can change the incentives that prisoners face and allow them to cooperate. If the prisoners are able to build a relationship in jail, for example, they might be willing to trust one another.

The identity perspective, meanwhile, is interested in the ideas that define the identities of the prisoners. If both prisoners are members of the same gang, then perhaps they will be compelled to cooperate; likewise, states with similar identities might have an incentive to act cooperatively in international affairs. If each prisoner is from a rival gangs, then perhaps they will be inclined to squeal; similarly, states with different identities might see an incentive to act against each other in international affairs.

These three perspectives seek to explain and predict behavior in the international system; however, the critical theory perspective (like some variants of the identity perspective) argues that it is difficult to abstract the behavior of states in the way discussed. Instead, deep historical and social circumstances are key determinants in the way events unfold.

There are other perspectives to the study of international relations.  A significant subset of perspectives are deemed “critical” theories or perspectives, as they deconstuct the study of international relations from the viewpoint of “the winners write the history.”  Feminism and Marxism, in particular, argue that the rules of international relations have been written by men and/or the dominant wealth holders.

The perspectives deal with the substantive causes of relations between states, while the levels of analysis locate the origin of the cause. By locating the cause at either the systemic, domestic, individual, or foreign policy level, we shift our focus of analysis. Do we look at the distribution of power among states (systemic) or do we look at the preferences of different states (domestic) as the potential explanatory factors for events? Levels of analysis are ways to locate the sources of causal factors.