This is a standard work of reference for the study of the religious history of western Christianity in the later middle ages which, since its original publication in French in 1981, has come to be regarded as one of the great contributions to medieval studies of recent times. Hagiographical texts and reports of the processes of canonisation - a mode of investigation into saints' lives and their miracles implemented by the popes from the end of the twelfth century - are here used for the first time as major source materials. The book illuminates the main features of the medieval religious mind, and highlights the popes' attempts to gain firmer control over the wide variety of expressions of faith towards the saints in order to promote a higher pattern of devotion and moral behaviour among Christians.