The truth is that none of these standpoints in isolation suffices for the student of Italy.  Her inner history is the history of social and intellectual progress evolving itself under the conditions of attraction and repulsion generated by the double ideas of Papacy and Empire.  Political unity is everywhere and at all times imperiously rejected.  The most varied constitutional forms are needed for the self-effectuation of a race that has no analogue in Europe.  The theocracy of Rome, the monarchy of Naples, the aristocracy of Venice, the democracy of Florence, the tyranny of Milan are equally instrumental in elaborating the national genius that gave art, literature, and mental liberty to modern society.  The struggles of city with city for supremacy or bare existence, the internecine wars of party against party, the never-ending clash of principles within the States, educated the people to multifarious and vivid energy.  In the course of those long complicated contests, the chief centers acquired separate personalities, assumed the physiognomy of conscious freedom, and stamped the mark of their own spirit on their citizens.  At the end of all discords, at the close of all catastrophes, we find in each of the great towns a population released from mental bondage and fitted to perform the work of intellectual emancipation for the rest of Europe.  Thus the essential characteristic of Italy is diversity, controlled and harmonized by an ideal rhythm of progressive movement.[1] We who are mainly occupied in this book with the Italian genius as it expressed itself in society, scholarship, fine art, and literature, at its most brilliant period of renascence, may accept this fact of political dismemberment with acquiescence.  It was to the variety of conditions offered by the Italian communities that we owe the unexampled richness of the mental life of Italy.  Yet it is impossible to overlook the weakness inflicted on the people by those same conditions when the time came for Italy to try her strength against the nations of Europe.[2] It was then shown that the diversities which stimulated spiritual energy were a fatal source of national instability.  The pride of the Italians in their local independence, their intolerance of unification under a single head, the jealousies that prevented them from forming a permanent confederation, rendered them incapable of coping with races which had yielded to the centripetal force of monarchy.  If it is true that the unity of the nation under a kingdom founded at Pavia would have deprived the world of much that Italy has yielded in the sphere of thought and art, it is certainly not less true that such centralization alone could have averted the ruin of the sixteenth century which gives the aspect of a tragedy to each volume of my work on the Renaissance.