Studies in the field of International Relations (IR) are taken into account by dividing the discipline into two or three schools. For example, it can be divided into three categories such as “traditional theories, global society theories and neo-Marxist theories” as Holsti accepted in his famous book “Dividing Discipline”, or it can be named differently such as “realism, pluralism and globalism” (Viotti and Kauppi, 1993). Barry Buzan identified the theories of international relations as “conservatism, liberalism and radicalism”. Indeed, realism, liberalism and Marxism are the fundamental divisions which are very common in different studies. On the other hand, Shimko used the basic division of realism and liberalism and further elaborated it with the division as Machiavellianism, Grotianism and Kantianism (Shimko, 1992: 283-84; Little, 1996: 68-69; Buzan, 1996: 55; Zacher and Matthew, 1995: 107; Smith, 1997: 12). There are some other categorizations which are not mentioned above, such as realist approach, rationalist approach and revolutionary/ cosmopolitan approach (Hedley Bull, 1993).

According to the realist paradigm, nature of human has important results for the international politics. For realist scholars, human is naturally sinful, egoist, interest oriented, aggressive and all the time power seeking in character. In particular, classical realism depends on the opinions of Carr and Morgenthau, and explains the international politics through human nature. Objective laws which dominate human nature must be understood to conceive international politics. In other words, as long as these laws are neglected, IR cannot be figured out. Naturally, humans are created with negative evil character and has passion and vanity (Shimko, 1992: 286; Buzan, 1996: 50). Morgenthau and Niebuhr among leading post war realists explain IR with human nature. According to them, just like individuals, states also have negative characters such as interest seeking and aggressive. States seek persistently to increase their power and capabilities to the extent that they can take other states under their control. Therefore, in such a structure, war and conflict are normal processes.

According to realism, states are the major actors of international politics. Their interests and the rivalry for getting more powerful, shapes politics. Multinational companies (MNCs) and international organizations are not assumed as actors of international politics.

Realists accept states as rational actors; that behave in accordance with certain rules and national interests to realize their objectives and to sustain themselves through national capacity (Viotti and Kauppi, 1993: 35; Grieco, 1995: 153; Buzan, 1996: 54; Senarclens, 1991: 11-12).

Hedley Bull (1993: 120-22), as stated above, classified the theories of international relations by three groups as realist approach, cosmopolitan approach and international society approach.

In contrast to realism or conservatism, Wilsonian idealism depends on Kantian liberalism, and it emphasizes the enlargement of the rights of individuals as a main point of concern.

As realist approaches focus on the security problems of the states in the anarchical nature of the international system, and pluralists research on how to realize peace and cooperation in the face of multi actors and their interdependent relations in terms of economic, political and social fields, globalist approaches criticize the reasons behind the underdevelopment of Third World countries in Asia, Latin America and Africa while other countries get richer. In general, Marxist writers are very interested in such debates, but non Marxist ones also pay attention to underdevelopment. Therefore, the IR theory is known as globalism instead of Marxism.

Dependency theories like pluralists are likely to accept the states, international organizations and nonstate actors as important actors. However, their main concern is to understand the uneven development of international economic system and its results. In particular, they focus on the dependency relations between industrialized northern countries (in North America, Europe and Far East) and underdeveloped poor countries in Asia, Africa and South America.

In 1970s, a new paradigm debate emerged in IR. This debate was a contention between state-centrism and transnationalism/non-state centrism. Transnationalism as a new paradigm was encouraged by the developments such as emergence of new actors and state-centric approach lost its attractiveness. At the same time, new international structure demonstrated that old fashion approaches couldn’t help to understand and explain new developments. In this framework, the writers such as Joseph S. Nye, Robert O. Keohane, Richard W. Mansbach and John A. Vasques who agreed with the description of David Easten for politics as authoritative allocation of values; claimed the necessity of changes in the statecentric paradigm. Henceforth, it is obvious that in the field of IR, the number of actors increased and differentiated extending from individual to the larger international social organizations. Political decisions are made and implemented in a very complex structure and sophisticated mechanism (Dougherty and Pfaltzgraff, 1990: 539).

Concerning the level of analysis and unit of analysis debate, the former is related to the causes and the latter is related to the results. In other words, unit of analysis is a dependent variable while level of analysis is an independent variable. In this context, level of analysis is the framework for analysis for the issue to be analyzed. Therefore, unit of analysis is an agent or a state the political behaviors of which is to be analyzed. In particular, if state-centric approaches are presumed then in general unit of analysis is a state and its foreign policy behavior to be analyzed. On the other hand, level of analysis is related to the framework the states as units of analysis are situated in. But level of analysis might change according to theories used for the purposes of an analysis. For example, if system theories are employed as framework for analysis, then, system is regarded as the level of analysis, whereas the state itself would be the unit of analysis (See, Buzan, 1995: 199, 203-204).

David Singer known by his contributions to the problem of level of analysis, in his well-known article titled “The Level-of-Analysis Problem in International Relations” (1969: 22), reduced the number of levels of analysis to two categories as: system level analysis and state level analysis.

For system level analysis, as mentioned above, the structure and distribution of power among the states are very important and determine the state’s foreign policy. Here, power configurations, changes of power and capabilities respectively formation of alliances and coalitions, stabilities and instabilities, international institutions and the changes in their structures are included to the analysis. In other words, in the level of international system, structure as a whole is taken into consideration for analysis.

Kenneth Waltz in his book titled as “Man, the State and War” (1959) analyzes the reasons of war through three factors and he has become the first scientist to start the debate about the problem of level of analysis. He demonstrated that the foreign policy could be analyzed by three ways such as state stemmed reasons, system oriented reasons and reasons depending on the human nature.

Epistemology The theory of knowledge or the theory of science. In other words, epistemology is to investigate the answer of “what is scientific knowledge?” and how is it produced? And in this context, there are three theories of knowledge or three epistemologies for scientific knowledge: empricism, rationalism and pragmatism

The basic feature of positivism as a methodological position and philosophical thought is that science is accepted only as valid scientific knowledge and acts are basic objects to be experimented on. This outlook is based on two important philosophical beliefs: 1) The main source of human knowledge is data (fact) and it is easily observed, 2) Data (or fact) is available only as a result of our senses.

Among the theories of knowledge, empiricism as a way of reaching-knowledge, the basic assumption is that true knowledge can only be acquired through senses and observations. So, empiricists don’t accept a priori knowledge, instead knowledge can only be gained by experience and the consequences of empirical observations. 

Positivism is distinguished by four important assumptions. First of these is the belief about the uniqueness of science. According to this assumption which is called as naturalism in philosophical language, there is no important difference between natural world and social world and through the methodology of natural science, social world can be analyzed. Second assumption is that there should be a distinction between facts and values. In terms of philosophy, this point of view which is known as objective position assumes that objective knowledge can be attained by scientific methods despite the existence of subjective factors influencing the research. Third assumption is based on the belief that as in the universe or natural world, there are also regularities in the social world. In this way, as research is carried out, either deductive or inductive methods are employed. According to the final assumption, research must be based on the methods of empirical verification or falsification (Smith, 1996: 16).

Positivism that denotes empricism, referring to scientific method was applied to philosophy by Saint Simon and further by August Comte, it became a noun of philosophical movement.

According to Waltz, in foreign policy of states, either the unit oriented reasons or system oriented reasons might be effective. Waltz asserts that regarding only one of these to analyze the foreign policy and the international politics is not enough. Instead, both should be considered to make right and healthy explanations and analysis. In short he adopts two track analyses, i.e. sometimes system level and sometimes unit level could be taken as an independent variable to analyze the foreign policy as a dependent variable. With his approach, Waltz has been the pioneer of neorealism/structural realism.

According to the Marxist theories focusing to explain war and peace through economic reasons, war and conflicts emanate from contradictions of capitalism.

Barry Buzan identified the theories of international relations as “conservatism, liberalism and radicalism”.