ABSTRACT
The twelfth and thirteenth century popes had struggled, not unsuccessfully, with the Hohenstaufen emperors: their successors were to find the national kings of Europe enemies as dangerous. The delimitation of the boundary between secular and spiritual jurisdictions had always been difficult, and it was likely to be more difficult. The power of the national kings, considered in relation to the spiritual claims of the papacy, was more compact and less vulnerable than that of the emperors had proved. It was more difficult to construct a society in which secular power should be national and spiritual power international, than one where both had been, at least in theory, international. This fact lies behind the weakness of the papacy in the fourteenth, fifteenth and sixteenth centuries, and accounts for the divisions of western Christendom at the Reformation.
