INTRODUCTION 23
tribes which in many respects is of the same order as that between divisions of the Ngwatd themselves. The same is true of the other societies with centralized governments.
This overlapping and interlocking of societies is largely due to the fact that the point at which political relations, narrowly defined in terms of military action and legal sanctions, end is not the point at which all social relations cease. The social structure of a people stretches beyond their political system, so defined, for there are always social relations of one kind or another between peoples of different autonomous political groups. Clans, age-sets, ritual associations, relations of affinity and of trade, and social relations of other kinds unite people of different political units. Common language or closely related languages, similar customs and beliefs, and so on, also unite them. Hence a strong feeling of community may exist between groups which do not acknowledge a single ruler or unite for specific political purposes. Community of language and culture, as we have indicated, does not necessarily give rise to political unity, any more than linguistic and cultural dissimilarity prevents political unity.
Herein lies a problem of world importance: what is the relation of political structure to the whole social structure? Everywhere in Africa social ties of one kind, or another tend to draw together peoples who are politically separated and political ties appear to be dominant whenever there is conflict between them and other social ties. The solution of this problem would seem to lie in a more detailed investigation of the nature of political values and of the symbols in which they are expressed. Bonds of utilitarian interest between individuals and between groups are not as strong as the bonds implied in common attachment to tnystical symbols. It is precisely the greater solidarity, based on these bonds, which generally gives political groups their dominance over social groups of other kinds.