As Arvind Thomas observes in the introduction to “Piers Plowman” and the Reinvention of Church Law in the Late Middle Ages, some of the earliest readers of William Langland's Piers Plowman were also practitioners of canon law, the system of ecclesiastical legislation that was codified in papal decrees and in the statutes of councils and enforced in the church courts. In this rich and thoroughgoing study, Thomas reads some key passages from the poem to reveal Langland's own immersion in canon law and argues that the poem itself makes a creative contribution to canonist thought. Piers Plowman engages directly with canon law in scenes where its allegorical characters come to confession or trial, and their interlocutors must establish the nature of their offences and assign appropriate penances. Thomas argues that these scenes not only dramatize the operations of canon law but also participate in producing it, reshaping and extending its categories and imagining the possibilities for its reform, with consequences for legal practice in the world beyond the poem. Like contemporary canonists, Thomas contends, Langland was engaged in a process of “finding” and “founding” the law, locating applicable concepts and categories in the existing texts, and establishing new precedents and possibilities through their application.

The first four chapters of this book are organized around the stages of the penitential process, while the fifth considers Piers Plowman's approach to penance as a whole, through its treatment of the documents and institutions that mediate this sacrament. In chapter 1, Thomas shows how Langland engages with the postures and gestures that the canonists recommended for penitents in confession—the kneeling, prostration, weeping, and blushing that were held to be conducive to contrition and expressive of it. When Mede laughs during her confession in the first vision, and when Contrition fails to weep as he makes his confession in vision eight, Langland reveals that neither figure is truly contrite, and he criticizes the friar-confessors who administer the sacrament without first encouraging this kind of response.

Thomas returns to the trial of Mede in chapter 2 to show how Conscience enlarges the canonists’ prohibition on usury when he speaks against her in the king's court. Conscience rehearses the usury prohibition directly in the B version of the poem, in a context that reflects its application to many different kinds of corrupt practice; in C, the explicit reference to usury disappears, but Conscience continues to think in terms of the categories that define usurious practices, invoking concepts of credit, time, risk, and doubt as he implicates Mede in an ever-wider range of crimes. Here, Thomas argues, Conscience makes his own innovative contributions to canon law, coining the expression “relacioun rect” to describe the social circumstances in which virtuous gift-giving occurs, and elaborating on the concept of “spiritual usury” (usura spiritualis) that was often alleged but rarely substantiated in canon law texts (C.3.343).

In chapter 3, Thomas considers Langland's treatment of a canon law maxim adduced by Repentance during the confession of Covetousness: “Non dimittitur peccatum donec restituatur ablatum” (The sin is not forgiven until the stolen goods are returned) (B.5.273a, C.6.257a). Repentance addresses the maxim directly to Covetousness in B, emphasizing the penitent's need to make restitution, but in C he speaks it as a general statement of principle, insisting that “þe Pope with alle his pentauncers” cannot absolve a usurious penitent who has not made restitution. Thomas argues that Repentance makes a new contribution to canon law in the C version, by extrapolating a binding law (ius) from a canonical rule (regula) and using it to govern the “relacioun rect” between penitent and confessor. Chapter 4 addresses another canon law maxim, “nullum malum inpunitum, nullum bonum irremuneratum” (no evil will be unpunished, no good unrewarded), cited by Reason during the trial of Wrong (B.4.143–44, C.4.140–41). Thomas shows how Reason transforms the trial of Wrong from a secular proceeding to a confessional interrogation in the scene where he cites the “nullum malum” maxim, so that its outcome has implications for the spiritual health of Wrong and his confessors. He argues that Piers Plowman develops its own, distinctive account of satisfactory penance in this scene, as Reason stresses the need to undertake socially productive manual labor (an emphasis that ran counter to contemporary trends in canonist thought), and imagines that confessors undertake a comparable form of labor when they interpret the penitential canons.

Chapter 5 explores the different responses to canonist thought in Piers Plowman B and C through a reading of the document that Patience describes for Haukyn in the fourth vision as he explains Christ's covenant with human beings: in B, he calls this document a “patente” and uses it to figure a direct, interpersonal relationship between humans and God, but in C he calls it a “chartre” and uses it to represent a relationship that is mediated by the Church (B.14.192, C.16.35). In this new emphasis on the institutional power of the church, the C version is more closely aligned with canonist thought, Thomas argues, yet it also innovates within the tradition of canon law by emphasizing the final fulfilment of this covenant on judgement day over its first formulation at the atonement.

This book offers a rich and provocative account of the way an allegorical poem might participate in the discourse of canon law and make its own, distinctive contributions to canonist thought. Thomas makes a convincing case that the early readers who encountered Piers alongside digests of canon law by Raymond of Peñafort, Henry of Susa, and William of Pagula could have understood these texts to be in a fruitful dialogue with each other. This is a book of precise, attentive close readings, but the arguments Thomas makes have implications for Piers as a whole, raising questions about retributive justice, productive labor, and the role of church institutions that are central to Langland's poetic project. In his account of “finding and founding,” variously elaborated with reference to medieval rhetorical categories and twentieth-century theories of metaphor, Thomas expands our own critical categories for thinking about the way medieval poems engaged with preexisting texts and reshaped the discourses in which they participated.