Much of Mannheim’s focus fell on the importance of “youth” in the analysis of generations. In stable communities (such as the European peasantry of the Middle Ages), youth is a simple biological distinction — the quality of being not yet old. But in times of social instability, youth becomes a source of difficulty, a problem. Mannheim was thinking of revolutionary eras, such as the early 19th century, when the movement from countryside to city was accelerating, and the status society of the restored monarchies was buffeted by a nascent bourgeoisie. It was a classic moment when the young people of a certain period became (in Mannheim’s terminology) an “actual generation”: “We shall therefore speak of a generation as an actuality only when a concrete bond is created between members of a generation by their being exposed to the social and intellectual symptoms of a process of dynamic de-stabilization.” Generations tend to get made by the people in them and by the times they live in when a span of time is felt by a biological cohort as one of crisis.