​This text was fundamental to the crystallization of structuralist theory in international relations. It addresses one of the discipline’s major dilemmas: the dialectic of the relationship between actor and structure. It reveals the shortcomings of the interpretations offered by the prevailing structuralist theories (neorealism and world-system theory), which failed to grasp the mutually constitutive nature of human agents and system structures, reducing the international system either to constraints imposed on actors or to structures generating behavioral patterns. However, by employing the “structuration theory” borrowed from sociology, US political scientist Alexander Want offers an expanded perspective that avoids reducing system structures to state actors (as neorealism does) or their reification in worldsystem theory. The scientific realist/structuration approach thus investigates the properties and dispositions of state actors and the system structures in which they are embedded, contributing to the reformulation of theoretical debate in the field of international relations, opening up broad horizons for understanding international dynamics and establishing a new research agenda that combines philosophical-scientific analysis with political-historical analysis.