It will be well to try to ascertain in what measure these essentials are found in a classification of European bodies politic under the five heads of tribes, cities, nations unitary and federal, and heterogeneous empires. Firstly, the classification is, I believe, so far exhaustive that it includes all those bodies which most clearly deserve to be called both political and European: it does not however provide a place for mere feudal principalities which never grew into nations, nor is it intended to include the Asiatic Empire of the Turks in Europe. Secondly, the marks which distinguish the classes are easily recognisable. Thirdly, the classification is decidedly imperfect because it does not make it impossible for a political body to be in two classes at once. But the possibility that a political body may be in two classes at once does not occur except during those periods when a community is gradually growing out of one form and into another. Such periods of transition have occurred in the history of many peoples: there was one in Greek history when the tribes were growing into cities: one in Roman history when the Republic was ceasing to be a mere enlarged city and was growing into a heterogeneous empire: and one in English history when the English were losing the character of a tribe and acquiring the qualities of a nation. But such periods of transition do not occur in the life of all peoples, and where they do occur, they are not usually of long duration when compared with the whole of the people's history. Fourthly, there are many important general propositions which are true of all or of nearly all the individuals in any given class. To establish such general propositions by historical evidence will be my task in the present chapters and in any future additions which I may be able to make to them. Some of these general propositions may be at once indicated in an imperfect form, though the proofs of them must be postponed.