Sovereign nations share the international system with a host of non-state transnational actors. Some of these entities have been created by states themselves, often as a result of the need to jointly solve a common problem, such as the United Nations. Other international entities are created when members of a society organize across traditional national boundaries to deal with a collective concern, such as Amnesty International or Oxfam. To understand and explain contemporary world politics we need to consider these institutions, as key actors influencing issues of war and peace. Although transnational actors are not new on the world stage, the number and type of these international entities expanded dramatically after World War II. This set examines both the rise of these new transnational actors and their effect on international politics and policies. Volume One: Causes - Why Do International Institutions Exist? Volume Two: Consequences - When, Where and Why International Institutions are Effective Volume Three: Types of Institutions - Security and Economic Volume Four: Types of Institutions - Environment, Human Rights, International Courts, Multilateralism, Regionalism