The crisis of European constitutional law in the interwar period was not merely the collapse of parliamentarism or the failure of liberal states; rather, it was a crisis in the legal understanding of the constitution itself. The formal constitution, understood in the liberal tradition as a supreme legal document and an instrument for limiting power, lost its explanatory force in the face of mass parties, executive concentration, social polarization, and the transformation of sovereignty. This study aims to explain the emergence of the concept of the “material constitution” in interwar Europe and to analyze its relationship with the crisis of constituent power, the transformation of the state, and institutional order.

The study employs a descriptive-analytical method with a historical-conceptual approach. Costantino Mortati’s theory is reappraised within the theoretical field shaped by Hans Kelsen, Carl Schmitt, Rudolf Smend, and Hermann Heller, so that the constitution may be understood not merely as a text, but as the point of intersection between norm, power, institution, and society.

The findings show that Mortati’s theory, despite its connection with a historically and politically problematic context, provides a way beyond the simple dualism between Kelsenian normativism and Schmittian decisionism. For Mortati, the material constitution neither negates the formal constitution nor submits to the raw reality of power; rather, it refers to the institutional and social layer that sustains the constitutional text.The significance of the theory of the material constitution lies in revealing the gap between the written constitution and the institutional reality of power. It shows that a constitution without institutional and social support may remain formally valid yet practically ineffective. However, the material constitution can serve constitutionalism only when accompanied by the rule of law, separation of powers, fundamental rights, and accountability. Mortati’s main contribution is thus the opening of a path toward “institutionalized constitutionalism