The aim of the book is clearly stated on p. 19: it is to provide ‘a detailed analysis of how these conciliar canons emerged from or affected legal culture and ecclesiastical government during that period’, and the author achieves it.

Her main finding is that both in their genesis, and in respect of their reception, the 1179 canons do not seem to be a very different kind of law-making from papal decretals, at least as the latter have been interpreted in more recent scholarship. Like decretals, they are in large part responses to pressures from below, including tricky legal situations with which the pope had been dealing at a more local and specific level; and, like decretals, their subsequent legal force depended a lot on how they were used by canon lawyers.

The development of the book follows the two-fold structure of the questionnaire behind it: first the genesis and then reception of the conciliar canons. On the genesis of the canons, Summerlin concludes that the council was not pushing forward a long-term over-arching papal programme (though ideology of papal supremacy was implicit). ‘There appears to have been a genuine attempt to promulgate conciliar canons grounded in the problems and disputes that had come to papal attention before the council … All the issues that the canons tackled had been brought to papal attention within the previous decade’ (p. 91). For example, there had been a movement to set up colonies for lepers (not very clearly distinguished from infirmi, people who were just ill) along lines in some ways analogous to religious communities. Canon 23 of the council gave such colonies rights to a cemetery, chapel and priest and some tithe exemption. The extent of the tithe exemption had however been the subject of recent dispute: the parish churches pushed for their rights. The council ruled with a compromise: tithe exemptions on gardens and animal fodder. Summerlin notes (p. 91) that this seems to match Alexander's compromise solution in recent cases. Other examples of a correlation between conciliar canons and recent real cases relate to excommunications and appeals, and to the place of military orders in church hierarchy.

The book notes a significant absence: canons on lay marriage. An ingenious argument takes off from Charles Duggan's thesis that Alexander preferred to deal with marriage problems on a case by case basis. Summerlin agrees that Alexander seemed to want to avoid general legislation on this topic, and infers the converse is that he did want general legislation on the subjects covered by the conciliar canons.

A major section is devoted to the connection between them and the newly emerging academic world. The 1179 council includes some canons borrowed from the Lateran Council of 1139, but not included in Gratian's Decretum. This is an important finding. Summerlin is right that it does not look like coincidence. There would seem to be an intention to fill a gap in Gratian: there is a ‘targeted repetition of canons that were omitted from Gratian but recognised as important’ (p. 122). That intention however presupposes a close knowledge of his Decretum. Summerlin's observation therefore fits well into her more general analysis of the relation between her council and the proto-university Schools. This continues with identification of connections between the (relatively new) tradition of academic commentary on the Decretum and the council canons. Canon lawyers were heavily influenced by Roman law, and the influences that she traces include elements of the latter: rules against promising a benefice when the holder was alive, and the rule of the two-thirds majority (only for papal elections) rather than the traditional ‘greater and saner part’.

Most of the rest of the book is about the reception of the council. There ‘appears to be little or no uniformity’ in the number or text of the canons across either the narrative or the manuscript traditions (p. 146) – ‘no single version of the canons was disseminated across Christendom’ (p. 160); ‘no one canon appears in the same place in every tradition’. Summerlin uses the phrase ‘fundamental confusion’ and speculates whether ‘the canons were held on loose leaves – or wax tablets – that were jumbled together in clerical luggage during the journey home from Rome’ (p. 166). Similarly there is textual variation: so, in the papal election decree, some manuscripts specify a three-quarters majority rather than a two-thirds majority. This may be the result of scribal error but other textual variants suggest confusion among participants about what the final version was: ‘no one “official” copy left Rome to be broadly disseminated … there was no mechanism by which the canons could be disseminated that would ensure that every cleric used the same – or even a closely similar – text’ (p. 181).

It took time for the 1179 canons to sink in to the collective consciousness of the educated clergy. Popes, it is true, used the canons as one might expect, as authorities to cite, or sometimes to modify. As usual, they reacted rather than initiated. The papal Curia aside, the use of the Third Lateran Council takes less predictable forms. At first canonists were unsure in what genre to classify them, and what kind of authority to assign to them. Local synods seemed not to consider them particularly noteworthy. Only from the late 1180s did the conciliar canons have an evidently major impact. Why then? Summerlin's answer is ‘the schools, which link the papal curia and the episcopal familiae’.

Throughout, Summerlin uses manuscript evidence intelligently, shining a strong scholarly torch on dark places in the thickets of textual and manuscript data provided by earlier scholars in highly technical studies. She is at home in the major scholarly languages, notably German, so crucial in this field. Her laborious and skilful work makes for a dense text, but there are clear conclusions to each chapter. Her findings are striking and, to this reviewer, convincing.