The strong do what they can and the weak suffer what they must.

The following definitions are from the book Understanding Global Conflict And Cooperation by Joseph S. Nye Jr. and David A Welch.

The building blocks

The state

The state is a political unit that has two important features: territoriality and sovereignty. By territoriality we mean that a state governs a specific piece of land. Sovereignty means that the state has absolute right to govern said piece of land. The word country is a decent synonym for state.

Oftentimes you will come across the term nation-state. In IR a nation is a group of people with common language, religion, history, etc (think ethnic-group). A nation-state is then a state where the inhabitants are vastly member of a specific nation. By definition then, there exist only a few nation-states today; Japan, South Korea, and North Korea.

Anarchic system

In contrast to domestic relations, there is no authority that rule over states. Yes, there are international laws and courts, but it is quite possible for a state to ignore them. This world order is called an anarchic system.

The theories of international relations

This list only include theories relevant to this web site.

Classical realism

Classical realism consider states to be the most important actors in international relations. What actions a state take against another state can be based on national conditions, as well as systemic pressures in the anarchic system. A pessimistic view on human nature is at the base, where one assume that humans, by nature, wants to dominate others. Classical realists is mainly concerned with power and security. Examples of classical realists are President Nixon, Henry Kissinger, and Machiavelli.

Structural realism

As with classical realism structural realism (also called neorealism) view the state as the most important units in the anarchic system. The main difference is that structural realists suggest that the choices of a state vis-a-vis other states is mainly dictated by the framework of the anarchic system. The focus of structural realism is first and foremost the balance of power in this system.

Liberalism

This theory acknowledges the anarchic system as well. States are important actors, but other actors are important as well (e.g. specific people, international help organizations, and companies). Contrary to realism liberalism has a positive view of human nature, where the main goal is to have a good life. Liberalism focus on progress, prosperity, and security.