This chapter provides a history of the idea of custom both in definitions and as presented in texts about lay legal life before the coutumiers. The first part of the chapter examines the struggle to define custom from late antiquity to the time of the coutumiers. It shows that thinking about and defining custom in its legal capacity was no obvious thing: while there where common definitional elements, the quest to define custom was marked by debate and a lack of consensus that would continue into the fourteenth century.

The eighth and final chapter examines the larger effects of textualization and vernacularization. The combination of the new technology of writing with the social choice of the vernacular permitted ideas about custom to circulate beyond their traditional local community ambit. Previously rooted laws and customs grew legs, and customary legal ideas could be transmitted though the circulation of texts and shared outside their local setting. In fact, this is when we start seeing the term ‘common law’ appear in French texts, a term scholars associate in this period with either royal law in England or with Roman and canon law as law that was common to Europe. This French ‘common law’ has been hotly debated. This chapter contributes to this debate by using the coutumiers to show how a French ‘common law,’ in the sense of a pool of common customary legal knowledge, was developing in France. This, in turn, implies more similarity between the legal cultures of France and England in this period than previously thought.

The thirteenth-century coutumiers capture a moment of intellectual ebullience. They were part of the formative moments of the lay courts and the theorization of ‘law in practice’ and in this sense the coutumiers were the linchpin of French legal thinking until the Revolution – and beyond in some French colonies. They created something powerful in the French legal imagination, so powerful that their use only increased with time and eventually became official law when the kings demanded coutumiers to be written for all the regions of France in the fifteenth and sixteenth centuries. This was all due to the ingenuity and intellectual creativity of the thirteenth-century lay jurists who borrowed, constructed, and effectively created a field of knowledge known as ‘customary law’.