This monograph both summarises and contributes to recent scholarship on the life and work of Gratian, compiler of the Concordia discordantium canonum (c. 1140), the work long known to canonists simply as the Decretum. It was this text with which students began their study of the canon law in the European schools. Fifty years ago there was a widely accepted view of Gratian's place in history. Probably a Camaldolese monk and also a teacher in Bologna, his work rendered all prior canonical collections obsolete. A lawyer in spirit if not in fact, he set the administration of the Church's law on a path separate from the one taken by theologians. These pioneering steps have justified Gratian's reputation as ‘Father of the Canon Law’, earning a place for him in Dante's Paradiso (Canto x.103–5).

Within these past fifty years, much of this account has been challenged. In 1979 John Noonan demonstrated that most of the received biographical information about Gratian was, at best, unreliable. We actually know almost nothing certain about him. Then, in 2000, Anders Winroth's Making of Gratian's Decretum announced a discovery of what appeared to be earlier versions of the Decretum. Instead of being later abbreviated versions, their texts actually contain the text as it left Gratian's hands. Winroth concluded that a large part of the text of the Decretum had in fact been added later by an unknown redactor. These challenges to the accepted account have provoked disagreement and also further research by specialists in the subject. This book is an example of the latter. The author's intent in it is to show that Gratian's interest in law was matched by an interest in theology. If so, the difference between Gratian's own contribution and prior canonical collections was less than has been thought. The Decretum was more theological in character than it now seems. The book raises the possibility (though the author does not say so) that Gratian himself deserves only a share in the title ‘Father of the Canon Law’.

The author's argument has two principal parts. The first shows that, as the compiler of only the original text, Gratian used the Bible more frequently and purposefully than later canonists would. Scripture ‘occupied the highest place in Gratian's doctrine of the sources of law’ (p. 35). Gratian's invocation of the example of Saul, who had continued to act as judge of the Israelites after he had been condemned by the Lord (1 Samuel xv), allowed Gratian to dismiss patristic authorities who had held that no deference was owed to the sentences of judges who were themselves guilty of serious and manifest crimes (p. 51). The point was of immediate relevance for the then current issue of the validity of the actions of simoniacal clergy. Adding support to his conclusion, Gratian pointed to the statement by Jesus that, despite all their faults, the Scribes and Pharisees still properly ‘sat in the seat of Moses’ (Matthew xxiii.1–2). Similar usage of biblical argument appears throughout the original Decretum.

The second part of the author's argument focuses upon the section of the Decretum known as De penitencia. It occupies the third quaestio within causa 33 and was probably a separate tract on penitence that was later turned into distinctiones for easier use within the schools. The nature and effect of the sacrament of penance dealt with in this quaestio were then controversial, and the book's treatment leads the reader into some deep waters. Must all sins or only some be confessed to a priest? Can public penance be repeated? What effect does confessing one sin and receiving absolution have on the status of other (unconfessed) sins? Do once forgiven sins return to count against the sinner if he repeats them? Gratian devoted considerable space and ingenuity to dealing with questions like these. The book also deals with them at length. Like Gratian, the author devotes less attention to other theological questions, but he explains the omission by arguing that Gratian's interests lay within theological matters that were then in dispute. Gratian felt no need to discuss issues that appeared settled when he wrote.

This monograph can profitably be read alongside Atria Larson's edition and translation of Gratian's Tractatus de penitentia. It appears as volume xvi of the same series. Whether the current interest and controversy surrounding the Decretum’s compiler or his intent will be resolved in the near future remains uncertain. One can only guess. But whatever the outcome turns out to be, Wei's book will have made a positive contribution to our understanding of Gratian and the nature of his place in the development of European law.