Realism, Liberalism, and Marxism are the three main theoretical positions that have shaped and dominated our understanding of the international world. Out of the three theories, Marxism has had the least influential role. Nevertheless, it should not be disregarded because it has a continuing validity in the study of international politics. Marxism claims that the politics of the world exist in a global capitalist economy. It argues that states are not the primary actors that must be considered when studying international relations; classes are. Economic strength is the determinant of how much power a region or group possesses. The international realm is an arena where constant class struggle is played out. Marxism argues that global capitalism ensures that the wealth and prosperity of the few will continue to depend on the exploitation of the many. The Critical theory school of Marxism presents some especially significant arguments that have shaped our understanding of the international world. .
Since Marx himself provided little insight as to how his theories should be attributed to international relations, many different schools of thought have emerged to stretch the philosophy to the global dimension. Although these schools differ significantly from one another, certain elements are central to all Marxian theories. All Marxian beliefs claim that the social world should be studied as a totality. This is important because no one area of social studies can be thoroughly understood without and knowledge of all the others. Another central belief to all Marxist schools is the contention that all historical and social developments are the products of the economic development of society. This is known as the materialist conception of history. Developments in the economic base of society lead to changes in the legal and political "superstructure" of society. Perhaps what sets Marxist theory apart from the other major IR theories is the value it places on the idea of emancipation.