The 11th century is commonly seen as the time when Western Christianity first drew strict moral and behavioural boundaries between the servants of the Church and the laity. Recent scholarship has indicated, though, that many ideas and solutions propagated then built on a legacy from up to two hundred years earlier. Crucially, the contribution of the 'long 10th century' (c. 880–1020/30) – a critical transition phase – remains for the most part unknown. While case studies have shown that commentators of this period were deeply preoccupied with the moral identity and conduct of ecclesiastical personnel in particular, a systematic investigation of surviving testimonies remains a major gap in religious and historical scholarship. In order to resolve this gap, the project will offer a detailed reconstruction of a large, regionally defined sample of narratives of religious distinction. This study is innovative because it transcends the focus of former scholarship on specific commentators and their work. Not only will it undertake an unprecedented comparative study of known commentaries, it will also considerably expand the body of primary evidence by including a range of narrative texts that have so far remained beyond the specialists' focus. As such, this project will award to the long tenth century the key place it deserves in the study of religious reflection and debate in the medieval West.