In its second edition, this introduction unfolds the world of medieval piety: Religion was taken for granted in the pre-modern era. Depending on the level of culture, it took on various forms and expressions. Characteristic of medieval piety is the way in which the book religion of Christianity penetrated an oral society and transformed it: Writing and reading, philosophy and theology developed. Religious practice manifested in various forms: veneration of relics, blood cults, endowments, indulgences, passion piety - an overall mix that cannot always be considered genuinely Christian. It is precisely in this blending of various elements that the tension lies; by the end of the Middle Ages, an almost explosive mixture emerges. This is made evident - contrary to the approach of earlier research, which was often confessional in nature.