The modern literature of comparative constitutional law and of general theory of the State has always tried to provide a satisfactory explanation for the various forms of autonomy that cannot be included in the classical phenomenon of the federal State.
Already in the final decades of the nineteenth century the literature on the distribution of political power from the “spatial” point of view underlined that it was impossible to interpret a wide range of phenomena only on the basis of the dichotomy Unitary State / Federal State (leaving aside the phenomenon of the Confederation).