Defining an entity so geographically, culturally and linguistically varied as the Latin west is difficult: despite the spectacular achievements of the Carolingians and Ottonians, fragmentation and plurality prevailed. Smaller political structures proved more durable, and, while the English and French realms gained sharper definition from the twelfth and thirteenth centuries on, the western empire became a loose federation headed by secular princes, lesser nobles and urban communities – all setting their own codes of conduct. New polities emerged on Christendom’s margins, adopting some Carolingian and Ottonian norms and administrative practices. The church – especially the papacy from the thirteenth century on – set the tone, holding kings and other secular rulers to account, while universities were both agents of clerical control and breeding grounds of dissent. But the range of participants in the political game was expanding, imposing limits on royal power, bringing access to additional resources and offering a potential counterweight to papal power. This was one of the west’s many paradoxes: strong elements of unity alongside the gravitational pull of many different centres.