In governing their dioceses late medieval bishops faced significant epistemological challenges: how was it possible to determine the truth in disputes over local customs, patronage, the conduct of divine service and the provision of pastoral care? All such problems demanded an adjudication between competing stories about rights, history and usage, and while canon law provided a framework of principles, it did not provide the answers bishops needed. Increasingly from the thirteenth century the answers came from panels of local ‘trustworthy men’. Bishops had to trust – to have ‘faith’ or belief in – informants who were often peasants. In the church courts and before visitation tribunals lay litigants, witnesses and parish representatives also used the language of faith and belief to characterize their knowledge of events and people: they had faith in their own perceptions. The role of faith in the knowledge that bishops and lay people claimed to have of the material and social world had much in common with the faith that brought Christians closer to having knowledge of God, but there were also important differences in the operation of faith in these three contexts. This essay describes and compares the epistemologies of late medieval bishops, lay people and theologians, paying particular attention to the relationship between trust and doubt in each instance.