The book by Georges Duby, one of the largest French medievalists, is dedicated to the social ideas of the Middle Ages. This is primarily a history of what medieval society thought about itself. But this is also a story about how such reflections correlated with reality, how they fit into more general ideological systems, what roots they had in previous eras and how they were developed in subsequent ones. If the geographical space of the study is outlined quite strictly - the North of France, then its mental space is by no means limited to the framework of one problem and one segment of history.