and research fellow at the USA Study Group, the Center for Strategic Studies
Realizing security is the main task of a nation-state and is the most important issue which is addressed by International Relations researchers. However, it is a very complicated, contradictory concept and mostly dependent on the approaches and theories which those researchers are using. So far, many different theories have been raised for description, explanation and prediction of security issues. The author attempts to illustrate developments in the concept of Security through the prism of developments in theories of security. Theories of Realism, Liberalism, Copenhagen School, Constructivism and also Normative theory are prominent theories which by raising different pre- assumptions and frameworks on national and international security have produced new horizons on security studies; they have raised different views on the main questions of security including reference, agent, aspects and means of realizing security. The topic of the present paper is surveying developments of the concept of security through prism of the above-mentioned theories.