Owen Phelan's monograph offers a rich and wide-reaching study of Christian formation in the Carolingian world. Building upon excellent recent scholarship on Carolingian correctio and early medieval baptism, Phelan argues that, under the Carolingians, baptism came to occupy a central place in the Christian reform movement and in the creation and maintenance of a Christian political community. In short, not only did baptism act as the ‘most basic organizing principle’ (p. 1) for the imperium christianum, but ideas associated with it also constituted the most enduring part of the Carolingian legacy. While these claims to overwhelming significance are somewhat overplayed, Phelan's work nevertheless serves as an important contribution which will be appreciated by scholars and students of early medieval Christianity alike.

Phelan engages convincingly with recent work – most notably, that of Mayke de Jong – which seeks to break down perceived barriers between the ‘secular’ and ‘religious’ in the Carolingian world. Chapter i, which skilfully traces the semantic development of the concept of sacramentum (to be rendered into English by the paired concepts of ‘oath’ and ‘sacrament’) sets the scene in this regard: as Phelan writes, there existed ‘a very deliberate correspondence cultivated by Carolingian leaders between civil and religious obligations anchored in the [imperial] sacramentum’ (p. 36). Phelan is undoubtedly right to highlight the dual significance of this concept, which structured inclusion in the Carolingian political order and in the Christian ecclesia alike. Yet while he argues convincingly for the importance of baptism as a sacramentum (pp. 42–7), the primacy that he allots to baptism among sacramenta in subsequent chapters is never explicitly demonstrated. At certain points, his analysis overreaches in this regard, for instance when taking Nithard's Historia, among other works, to ‘confirm that the sacramentum of baptism structured Carolingian moral analysis’ (p. 217).

Phelan's structure continues along broadly chronological lines, addressing, in successive chapters, the role of baptism in the articulation of religious and political authority, most notably in the Admonitio generalis (789) and at the Council of Frankfurt (794) (ch. ii); the conception of baptismal formation, or catechism, as expressed in the writings of Alcuin of York (d. 804) (chapter iii); the burgeoning interest in baptismal formation and the sacramentum of baptism, as documented in Charlemagne's circular letter of 811/2 and the responses it elicited (ch. iv); and finally the diffusion of these ideas to the laity, as revealed in works of Dhuoda, Jonas of Orléans and Nithard, as well as in liturgical and vernacular texts (ch. 5). It is capped off, appropriately, by a conclusion which discusses the afterlife of Carolingian ideas about baptism in late and post-Carolingian Europe. While such a structure elegantly reconstructs an evolving Carolingian discourse on baptism, at points it serves to confuse rather than to clarify, insofar as it impedes a synthesis of the themes and subjects which recur regularly throughout the book. Phelan offers, for instance, a fascinatingly utilitarian approach towards Carolingian liturgy, arguing, in contrast to previous literature, that Carolingian authors were not concerned with liturgical uniformity as an end in itself, but rather sought to harness the liturgy as a means of correct Christian education. This shrewd discussion, which ranges over three chapters (see especially pp. 124–8, 155–7, 171–2, 205–6, 256–9), would have benefitted from a more unified treatment. Similarly, Phelan's comments on extra-ecclesiastical processes of Christian formation – namely on the role of the godparents and families in Christian instruction – constitute a significant, if scattered, contribution (especially pp. 76–8, 158–60, 186, 216–17, 229–33).

Throughout, Phelan looks in depth at particular Carolingian tracts, offering detailed textual analysis. The inevitable result is that greater clarity is accorded to the Carolingian discourse of baptism and Christian formation than to the role of baptism in Carolingian society, though Phelan takes pains to connect the former to the latter. Here, Phelan is limited by his material: even chapter v, which explores the reception of this discourse by the Carolingian laity, allots half of its discussion to three texts written for or by members of the Carolingian elite (pp. 208–39). Only at the end of the chapter does Phelan turn to ecclesiastical language politics (pp. 252–61), on which his preceding comments on the role of the liturgy in Christian formation are predicated, thus broadening the implications of such discourse to a wide, subelite public. Notably absent in this otherwise comprehensive treatment is a sustained discussion of the Christian infrastructure through which Christian formation was transmitted, whether in terms of institutions or personnel. Phelan's arguments regarding the role of sermons in the process of Christian education (pp. 239–49) could have been strengthened by addressing the educational level of the Christian clergy and commenting on the availability of such texts in local churches. Likewise, further discussion of the role of local churches – and, specifically, of baptismal churches (addressed pp. 74–5) – could have helped to situate his discussion more concretely in the Carolingian landscape.

All in all, Phelan offers a vibrant study of the development of Carolingian thought on baptism and on the closely-interlinked process of Christian formation. While its wider implications – namely, the role of the sacramentum of baptism as the structuring principle of the imperium christianum – may occasionally be overstated, Phelan is to be commended for his detailed analysis of individual texts and authors and for his careful delineation of the development of Carolingian discourse on these topics.