When we speak of unity in this connexion we may mean one of three things. There is a unity of character or type. There is the unity involved in continuous unbroken descent from a common origin, and there is unity of effective interconnexion and mutual dependence. These senses of the term unity are confused by some writers, but must clearly be distinguished before any useful inquiry can be made. Unity of character, for example, is a different thing from continuity of historical development, for a civilization might radically change its character in the course of generations. It might lose all the specific features of its own family and come into closer resemblance with others of quite distinct parentage. Again unity of character is not the same thing as the effective interconnexion and co-operation of different centres. On the contrary, such co-operation is of most value where there is marked difference of character, where, for instance, a lack of a quality in one nation is counteracted by a surplus in another. Thus these three forms of unity are distinct, but if distinct they are not unrelated. Naturally, where there is a common origin, many traits of the primitive unity of character are likely to persist, and where there is effective intercommunication, many differences may be rubbed off. So, where we start with unity of origin, we are likely to find some measure of unity in other respects, and this is what we do find, in fact, in the case of Western civilization. It does possess a certain unity of character, and this is largely due to unity of origin, and is maintained in spite of marked divergences, which have not impeded an effective intercommunication but have tended rather to add interest and value to the results which that intercommunication has produced. SECTION I.--UNITY OF CHARACTER