The subject of my investigation will be the widespread acceptance of a variety of forms of Christian worship in medieval Western Europe beyond those performed or approved by the pope, even by those who would never have accepted a range of doctrines. To examine this issue, I cast a wide net on sources, starting with authoritative late antique authors like Augustine (354–430) and extending to late medieval thinkers like William Durandus (ca. 1230–96). Many papal letters that are essential to the argument must be consulted in manuscripts in Rome and Italy more generally. Most intellectuals tolerated others' worship, and the standards generated for what must be included in normative liturgy were minimal. This attitude extended to the papacy, which held that Christians should be unified through the same doctrines and structures of authority, not the same worship. The research is intended to nuance the view of medieval Europe as an oppressive persecuting society when applied to religious practice.