The culture of friendship in pre-modern Europe was broadly commensurate with political culture. Friendship could provide a conceptual vocabulary for almost any relationship of importance outside the ambit of close kin. Some notion of friendship seems to have been inextricable from most social or political institutions, such as patronage, lordship and military allegiance – indeed even ideas about kinship itself were interwoven with friendship. But it is hard to recover the precise role of so ubiquitous, even apparently commonplace, a concept. References to friends and friendship scattered throughout the texts of chronicles, charters, histories, letters, sermons and so forth, can easily escape our attention. The writers presumably thought in most cases that they needed no explanation. From the perspective of a modern culture in which friendship is valued as an essentially private experience, they can appear as mere clichés, as hollow as the notion of the friendship of nations. Yet friendship had been at the centre of the tradition of political thought since antiquity, and recent research has demonstrated its centrality to political life and social order in the Middle Ages. Gerd Althoff's work, for example, was among the first to show the importance of friendship to the functioning of order in early medieval society. His approach has been described as part of a ‘new constitutional history’. Huguette Legros, more recently, has demonstrated how the chansons de geste of the central Middle Ages reflect a comparable culture of friendship: ‘Avoir un “ami” c’est d’abord avoir un “allié” ‘. An increasing amount of research has focused on the impact of the friendship bond on the organisation of medieval society and the functioning of its politics, often recovered from scattered and cryptic references in the sources.

In the monastic world friendship is apparently less elusive. The heightened expressions of friendship found in monastic letter collections for example, or its treatment in sermons or treatises, are an important part of medieval literary culture. Such explicit interest in friendship flourished particularly in what has come to be known as the twelfth-century Renaissance.