The twin themes stated in the title to this Festschrift reflect the honorand's interests as a leading specialist in medieval canon law and a historian who has sought to trace the medieval origins of modern legal concepts, notably through the manuscript tradition of medieval ‘learned law’ (Roman and canon). This law was learned for it was the law taught in medieval universities, hence the editorial introduction stresses the consequent interplay between jurisprudence and church law, legal learning and other disciplines, and legal theory and practice, emphases that are reflected in the essays gathered in this volume. The contributors comprise Europeans and Americans, indicating the honorand's reputation in his native US and beyond, and the international nature of his field; the twenty-six essays include ten in English, nine in German, four in Italian, two in French and one in Spanish. The editors, Pennington's former pupils, arrange these under four headings. The first refers to ‘An age before Jurists, c. 500–1140’. Körntgen's essay examines the growth of penitentials in this period, and focuses on one which comprised canon law collections. Conversely Hartmann's study of Regino of Prüm's ‘Sendhandbuch’ (a ninth-century canon law manual) identifies penitentials among its sources; his and Schieffer's essays also explore the ninth-century origins of diocesan courts, for which such manuals were compiled. In this period diocesan judges were apparently itinerant, as were Chorbischöfe, the wandering representatives of ‘full’ bishops (later superseded by other episcopal subordinates) who are the subject of Jörg Müller's essay. Meanwhile Schmitz and Austin's essays concern the emergence of canon law collections alongside these institutions, including a Carolingian codex at Barcelona comprising capitularies, conciliar and decretal material (Schmitz), and the better known Decretum of Burchard. Austin finds in the latter an innovatory condemnation of private vengeance based partly on the compiler's experience as bishop of Worms. The second group of essays treats ‘Authors and texts, c. 1140–1350’. Four concern Gratian's Decretum, the first generally accepted canon law collection in the medieval west. It has been the subject of much recent scholarly debate and research, centring on the idea that the Decretum evolved through at least two and possibly multiple ‘recensions’ from the early to mid-twelfth century. Winroth, the chief proponent of this idea, sees theological influences on the ‘first recension’, notably in its approval of marriage for the unfree, which departed radically from Roman law. Lenherr finds another innovation in Gratian turning the Church's official stance on the death penalty from consent to opposition. Sommar's case study concludes that such legal evolution did not end with the final recension of Gratian's text, but continued in the dialogue among its twelfth-century commentators. Larrainzar, who favours the ‘multiple-recension’ theory, finds evidence to support this in the changing form and content of the preface to the Decretum (two different prefaces occur in the manuscripts). Four other essays concern post-Gratian canon law and its commentators. Somerville notes an unknown French glossed fragment of the Compilatio prima, the model for subsequent collections of papal decretal law. Landau identifies the late twelfth-century glosses on another collection (‘Cassellana’) as possibly the work of the first German commentator on decretals. Kendall focuses on Innocent iii's decretal ‘Vergentis’ as evidence for Pennington's controversial theory that this pope was more of a theologian than a canonist. Finally, Donahue analyses the neglected contribution of Johannes Faventinus to the canonistic debate on marriage formation and suggests that he influenced Pope Alexander iii's important decretals on this issue; but his argument rests on the uncertain dating of these decretals and he revisits this question in an appendix. Part iii of the volume focuses upon ‘Courts and procedures, c. 1140–1500’. Brundage describes the rules that governed an advocate's relationship with his clients in the later medieval church courts. Condorelli edits and analyses three quaestiones of a late thirteenth-century Italian canonist that concern usury, notably the usurer's testamentary obligation to restitute his ill-gotten gains. Kéry traces the development of ecclesiastical penal law and concludes that the work of the canonist Bernard of Pavia (d. 1213) marked a turning-point by differentiating between penance and punishment. Lepsius observes the influence of canon law on late medieval secular justice in northern Italian cities, notably in their adoption of syndics (appeal judges) and summary procedure. Ascheri surveys the church court records for late medieval Siena, while Schmugge studies a German petition to the papal penitentiary that describes a complex marriage case and illustrates the fifteenth-century laity's knowledge of canon law and their access to courts and skilled lawyers. Part iv concerns ‘Canonists in conversation with the wider world’. Roumy illustrates such dialogue between canonists and other disciplines by tracing the origins and diffusion of a legal maxim, derived from classical sources and transmitted by canon law to theology, Roman law and even philosophy. Likewise de Miramon responds to Pennington's theory about Innocent iii by showing evidence that the future pope's studies at Bologna were probably in theology and natural philosophy, not canon law. Bellomo considers the ‘pervasiveness of religion’ in medieval universities, notably their close relationship with ecclesiastical authorities and clerical provision of accommodation and pastoral support for students often far from home. Erdö summarises the evidence for a canon law culture in late medieval Hungary and Poland, notably the presence of local church courts, university-trained lawyers, canon law books and synodal legislation. Tierney studies William of Ockham's use of canonistic texts in his Opus nonaginta dierum, particularly his invocation of natural rights in the Franciscan poverty controversy; Tierney holds that Hohfeld's work on legal ‘rights’ clarifies such medieval usage of the term. Finally Helmholz assesses how much a famous English common lawyer, Thomas More, knew and respected canon law, concluding that he made some use of it, notably regarding heresy, and defended it, but recognised the limits placed upon it by the secular law and showed a humanist's impatience with its intricacies. This rich and varied volume closes with a list of Pennington's published works from 1970 to 2005 and a brief index.