The struggle against any form of simony, the implementation of the command to celibacy, as well as the elimination of the influence of the laity in matters to do with the Church were the most important aims of the popes from the middle of the eleventh century. They presented their requests increasingly in numerous synods, called for and led by themselves, to the extent that these councils came to be seen as a characteristic of the Reform Papacy. They run like a red thread through the pontificate of Pope Urban ii, from whose ten-year pontificate ten such synods are known, all of which concern themselves essentially with the themes mentioned above. It is these synods that have concerned Robert Somerville for decades and for the synods of Melfi (1089), Benevento (1091), Troia (1093) and Clermont he has already produced exemplary editions, which have been expanded upon and illuminated in several studies. So in this book, which concerns the Council of Piacenza, previous and new studies are summarised, expanded and systematically treated. At the centre of the discussion stands the critical sifting of the comprehensive manuscript transmission of synodal decisions, for which Somerville has examined over forty manuscripts (pp. 29ff., 71f.). None of these codices go directly back to the papal chancellery, but they all relate to copies, mainly from the twelfth century, and demonstrate few internal differences. The contexts and mutual dependence of these illustrated transmissions, designated by Somerville as ‘textus receptus’, are described and discussed with great perceptiveness and acumen, the result of which is to show, in spite of considerable effort, that, on account of the faulty nature of the sources, no unambiguous conclusions can be arrived at, so that at the end of a discussion more often than not a conclusion of ‘non liquet’ (p. 29) or ‘There is no way to know” is arrived at (pp. 109–11). The result of these text-critical studies is the edition of the decisions of the Piacenza (pp. 89–99), for which, and on good grounds, the Codex Paris, BNF lat. 3881, a manuscript of the collection of canons of Cardinal Gregory of San Grisogno, is chosen as the basic text. The readings of the other manuscripts form the partially comprehensive apparatus of variants. This is supplemented with further decisions of the Synod of Piacenza which are contained in some collections of canons and in historiographical and polemical works such as the Gesta romanae ecclesiae contra Hildebrandum of the cardinal priest Beno from the end of the eleventh century. Attached to the edition is a translation and a detailed commentary on the canons, the major themes of which are the struggle against simony and the validity of the consecrations of the imperial pope, Clement iii (ch. v, pp. 102–15). These studies are accompanied by discussions of the date, location of council and participants as well as detailed reports in the gesta of Cardinal Beno and in the chronicle of Bernold of Constanz. In the final chapter Somerville presents important comments on the poor transmission of and unresolved questions relating to the subsequent councils of Urban ii to the end of his pontificate (pp. 116–33). This strikingly penetrating study concludes with a comprehensive bibliography, a list of councils and manuscripts and a register of persons, places and subjects.