Military institutions are a vivid reflection of social order and social change, particularly in eighth and ninth centuries. Social history, more than any other branch of historiography, is compelled to adopt explicative theories which often remain hypothetical. With a knowledge of medieval social concepts, one can better understand the thought of the former times. Social order represented the theoretical and structural classification of medieval society, social life was rather determined by the various relations between people or classes, by natural or 'artificial' bonds between human beings and groups on an equal as well as on a hierarchical level. The family was the most natural and primary social institution at all levels of society. The household and manorial systems were more than mere social bonds in so far as they at the same time represented forms of community life within a certain social context: on the one hand the family, on the other the seigneurial familia.