Henry Mayr-Harting's book is the result of many years research into intellectual life at Cologne in the tenth century. It is the culmination of a long-standing interest in the world of Bruno, brother of the Emperor Otto i, archbishop of Cologne and duke of Lotharingia, and represents a vital contribution to scholarly understanding of the importance of Cologne, a nub of Ottonian ecclesiastical and political rule. Crucially, he demonstrates that in a context where politics was patrimonial and non-centralised, individual centres such as Cologne provide insight into the shape of Ottonian rule.

This work focuses on annotations found in manuscripts surviving at Cologne – an important though much neglected source for the intellectual underpinning of imperial power. Mayr-Harting has already demonstrated how Ottonian art illumines the society and culture that created it. This work represents a crucial addition. Glosses are skilfully deployed to show how actual politics and intellectual life at Cologne in the period c. 950–1050 were closely intertwined. Through the lens of Ruotger, Bruno's tenth-century biographer, as well as extant scholia, Mayr-Harting brings attention to the intersection between Ottonian Realpolitik and ruler ethic.

Church and cosmos in early Ottonian Germany is unique in a number of respects: it provides a detailed study of intellectual life at Cologne in the tenth century, edits and examines for the first time one of the earliest known corpus of glosses to Boethius' Arithmetic, expands current knowledge of the importance of Platonism before the twelfth century and shows how some of the central texts of the Middle Ages were read by tenth-century scholars at Cologne. Its broad sweep is rooted in rigorous manuscript work and detailed exploration of various kinds of marginalia, ranging from nota monograms to glosses.

The introduction is in the tradition of Althoff, Bernhardt, Leyser and Reuter. Mayr-Harting provides a concise survey of Ottonian politics in the tenth century. Familiar themes are explored with fresh insight, specifically to understand the intellectual culture of rule and the ideals of Ottonian churchmanship. Mayr-Harting integrates Ottonian economic, political and cultural developments with the details of Bruno's life and Ruotger's biography. The political and sacral significance of itinerant kingship, understood in a context where rule was face-to-face and aristocratic loyalties were strongly regional, provide a focus for Ruotger's Life and the growth of Ottonian ruler ideology. More specifically, the importance of regional politics is examined as a means of understanding the career of Bruno. Mayr-Harting studies the strategic role of Lotharingia against the backdrop of Bruno's mission as archbishop and Ruotger's Gregorianism. In addition, he demonstrates that Ruotger's use of an episcopal model in the Gregorian mould is not only an attempt to justify Bruno's combination of ecclesiastical and military office against his detractors, but reflects a specific interest in Gregory at Cologne, evident in the early efforts made to assemble his writings there, as well as in marginal notae found in manuscripts surviving at Cologne. Here Mayr-Harting makes a vital observation: Gregory meant different things in different periods in Cologne. On the evidence of marginal notae found in Dombibliothek, ms 94, he highlights the shift away from the Trinitarian and Christological interests of the Carolingian period found in ms 92 into the world of Ruotger, with its interest in the active and contemplative life.

This book's principal contribution is to show how many of the central texts of the Latin west were read at Cologne in the mid-tenth century and how the extant glosses, studied with an eye to Ruotger, help to illumine the intellectual context of imperial rule. Apart from the works of Gregory, the texts studied are Prudentius' Psychomachia, Boethius' Arithmetic and Martianus Capella's De nuptiis Philologiae et Mercurii. All three works were at Cologne by the late tenth century, as is evident from the extant cathedral manuscripts. Mayr-Harting brings together much evidence to show that the eleventh-century Prudentius manuscript (Dombibliothek, ms 81) is based on a tenth-century exemplar. This enables him to demonstrate a shared thought-world. For example, he notes a congruence between the ecclesiological slant of the glosses in ms 81 and the ecclesiological interest of Ruotger's Life, as well as the shared interest in peace.

For Boethius' Arithmetic, he deploys a similar method. He notes the interest in the liberal arts in Ruotger's Life and other tenth-century Cologne sources as evidence for the acquisition of Dombibliothek, ms 186, a manuscript in which Boethius' Arithmetic and Macrobius' Commentary on the Dream of Scipio are bound together. His contention that Martianus was little used as a source for arithmetic is, however, somewhat complicated by the evidence of manuscripts like Leiden, Universiteitsbibliotheek, ms Voss. Lat. F. 48. Dating to the first half of the ninth century and transmitting the oldest gloss tradition to Martianus, it has heavy glossing to book vii.

Mayr-Harting's edition and study of the glosses on Boethius' Arithmetic found in ms 186 makes a significant scholarly contribution. The glosses reveal the interplay between arithmetic and cosmic ethical awareness and are generally of the same thought-world as that of Eriugena. Even those on superpartients display an interest in unity and multiplicity, divisible and indivisible nature, thus demonstrating that the study of arithmetic at Cologne was less about calculation than about a universal order of creation in the Platonist sense, an understanding fundamental for concepts of imperial authority.

In his study of the glosses on De nuptiis in Dombibliothek, ms 193, Mayr-Harting continues the Platonic/cosmic theme. Notable is his discovery of a number of relatively rare additions in the Cologne manuscript and Leiden, Universiteitsbibliotheek, BPL 36, leading him to conclude that the two manuscripts drew on a common exemplar. And since Leiden, ms 36 has features which point in the direction of Lorsch, he suggests that the additions probably came to Cologne via Lorsch, especially given the close connections between the two at the time of Bruno. His conclusions are supported by the evidence of Paris, BNF lat. 8671, whose glosses are largely not considered. The annotations in the Paris manuscript, however, are related to those in ms 193 and Leiden, ms 36 and may very well emanate from Lorsch. One notable feature of the additions in ms 193 is the interest in fables and their role in presenting truth, reflecting the wider debate on profane learning and its appropriation in the early Middle Ages.

This book eschews the danger of representing intellectual life at Cologne as monolithic. Rather it favours the specific and the particular. To this end, Mayr-Harting's perceptive insights, drawing on an impressive range of evidence, present a compelling picture of how regional interests reflect wider issues and how some of the central texts of the early Middle Ages were read in tenth-century Cologne and helped to articulate an Ottonian ruler ethic.