Yet Italy profited less than any other state from the lessons which she taught. France, England, and Spain, all of them the pupils of Italy, became strong, united, and wealthy states, while Italy herself, in the very middle of an intellectual and artistic activity which has remained the wonder of the world, subsided into political insignificance, and only finds a place in subsequent history as the stage on which other nations fight out their quarrels. The solution of this crucial problem, the combination of intellectual progress with political decadence, can only be found in a careful study of the conditions which [Sidenote: Causes of Italian disunion.] prevented the people of Italy from following the normal tendencies of the period, and becoming a nation. The causes of disunion are too numerous and deep-seated to be summed up in a few sentences. But it may be instructive to form a clear conception, at starting, of some of the most notable conditions which influenced the course of Italian history in the period which we have to consider. In the first place, geography in Italy, as in Greece, tended to disunion. The Apennines cut off the Lombard plain from the rest of Italy, and divided the latter into two unequal parts which were again split up by the lateral offshoots into divisions, not quite so small as those of Greece, but almost equally marked off. The nominal subjection to an elective emperor, who was also king of Germany, rendered impossible the rise of any strong native power which could weld together the separate political units. The influence of the Papacy, which in the thirteenth century combined the sovereignty of an Italian state with the spiritual headship of Latin Christendom, proved almost as great an obstacle as the Empire to national union. The great length of Italy, by increasing isolation, hindered the growth of common interests. The leagues occasionally founded for common aims, such as the Lombard league against Frederick Barbarossa and the league of Venice against Charles VIII., were never more than temporary alliances, and fell to pieces as soon as their immediate object was gained.