The term ‘Christological debates’ might conjure up memories and images of the councils of Nicaea or Chalcedon, or of the emperor Constantine administering and adjudicating the various sessions at Nicaea as delegates sought to delineate the orthodox conceptualities regarding the nature of the Son and his relationship with the Father. Then many tend to regard – and quite erroneously so – Christological debates as settled matters by the time Lutheran reforms and revolution (depending on which side of the ecclesial Rubicon one viewed his indefatigable work) split western Christianity by the mid-sixteenth century. However, as Richard Cross rightly notes, the renaissance of Christological issues during the Reformation period was reflective of reverberations and reformulations of patristic and medieval perspectives. Cross's preface situates the literary provenance of this erudite – at times recondite – volume; he is a medieval philosophical theologian of the first order, thus whilst his approach might strike as ‘unconventional’, the benefit of having a medievalist visit the topography of Reformation polemical terrains is considerable. Even though he prescinds from offering a contextualised narrative from politico-historical type, Cross more than amply makes up for it by offering a robust patristic and medieval contexualisation. He alerts the reader that as ‘is appropriate in a work that is intended to be paradigm-changing, I shall destroy some shibboleths in the history of theology, or at least attempt to … because close attention to the texts seems to me to demand it’ (p. 38).

As a perusal of ‘Frequently cited principles’ gives fair warning (pp. xxiii–xxiv), this book will require a patient and philosophically-adroit reader, with no less than twenty-two ‘semantic principles’ deployed throughout this dense yet illuminating work. In chapter i, Cross offers a scintillating analysis of the Christological/eucharistic divergence between Luther and Zwingli with a close reading of the metaphysics and semantics of their respective views on the ‘hypostatic union’ of the divine and human natures of Christ, and the specific ways their disagreement over Communicatio idiomatum influenced the fall-out of Luther-Reformed agreement over the specifics of the location, presence and significance of the body of Christ in the eucharist. Cross throws down his gauntlet to offer an interpretation of Luther's Christology which differed in ‘marked respects from that which we find in most interpreters’ since ‘Luther's tendency to exaggeration and rhetorical excesses can sometimes tend to obscure his positions’ (p. 39).

Simultaneously, in contradistinction to, and extension of, chapter i, Cross depicts in painstaking detail the Christological developments within early Lutheran Christologies, of Philip Melanchthon, Johannes Brenz and Caspar Schwenckfeld. Particularly illuminating is how Cross shows the developmental trajectory of Brenz's Christological perspectives. Brenz was not merely a gifted church administrator among the pro-Luther evangelical camp; according to Cross, his Christological development merits a closer scrutiny. By situating the origins and further fine-tuning of Genus maiestaticum, which both influenced and was impacted by Brenz's confrontation with John a Lasco at the Colloquy of Stuttgart in 1556, Cross successfully demonstrates how Brenz's – and all other interlocutors’, for that matter – Christology was formed in situ, not only vis-à-vis his contemporaries but also in deep dialogical engagement with patristic, conciliar decrees, further refined and refracted through the medieval lenses.

Yet Communicatio idiomatum is more than simply the definitive revisionistic philosophical-theological account of the oft-inordinately abstruse – thus oft-avoided by historians – terms of debates among the Lutherans, Calvinists and (though they are missing in Cross's narrative) Catholics. Both in terms of cast of characters and the insights offered, Communicatio idiomatum will be the first port of call for anyone interested in better informing her/himself of the complexity and nuances of this, again, oft-overlooked chapter in the theological reconfiguration of the early modern era, with deep connections to and influences by the patristic and medieval perspectives on metaphysics of divine personhood, and how the human person of Jesus accommodated and reflected how its ontological specificities are to be approached in eucharistic theologies.

A main pivot in Cross's argument is in paying particularly close attention to the key theologians’ metaphysical and semantic assumptions that have often gone under-analysed, if not altogether missed. Cutting through the thickets of subtle distinctions and differences, Cross applies his own Ockham's razor and offers a helpful three-fold typology of Lutheran Christologies: ‘Melanchthonian (Wittenberg); non-Brenzian majestic (largely students or associates of Melanchthon working outside Wittenberg); and Brenzian (Württemberg/Tübingen)’ (p. 121). Such a helpful triptych allows the reader to appreciate the complexity of the division in a relatively simple way. Similarly, Cross offers a brilliant analysis of Calvin, Joachim Westphal and Tilman Hesshus – the two redoubtable defenders of the Lutheran view of the bodily ubiquity of Jesus vis-à-vis Calvin – in chapter iii. In the sections ‘Vivification and bodily presence’ and ‘Vivification and causal presence’, Cross shows in detail how these three interpreted the significance of Christ's eucharistic presence and how that theo-logic and grammar of grace needed to be parsed out.

A surprising protagonist in Cross's revisionistic narrative turns out to be Johannes Brenz, not Luther, Zwingli, Calvin, Bullinger or Melanchthon. Yet, Cross's exaltation of the significance of Brenz's Christology for an enhanced understanding of the period and issues at stake is duly warranted. Particularly refreshing is the way in which the Colloquy of Montbéliard (1586) is presented in chapter vii. In typical fashion, Cross offers a close reading of the divergent Christological semantics and metaphysics of Jakob Andrae the Lutheran and Theodore Beza the successor to Calvin in Geneva. For Cross, ‘Andrae's contribution to the discussion at Montbéliard gives the fullest account of both the metaphysics and semantics of the hypostatic union as construed along broadly Brenzian lines’ (p. 227), which ended up revealing the not so insignificant gaps in Andrae's understanding of the hypostatic union. His meticulous combing of sources leads Cross to offer a succinct encapsulation of the Brenzian Christology, seen in Andrae's Acta colloquii Monte Beligardensis (Tübingen 1587): ‘In this expression, “This man is God”, the term “man” means a true man . . . which consists of a body and a rational soul, namely, Jesus the Son of Mary of the seed of David; and the second term “God” means the true and eternal, essential Son of God . . . ; and the third, the word “is”, retains its own proper meaning, by which something that is expressed is said actually to be and exist’ (p. 227). Thus for Beza and Andrae then in 1586, and perhaps equally importantly, for Cross and contemporary readers, this statement outlines the terms of division then and now.

The ‘concluding remarks’ help recapitulate the themes that Cross sought to investigate. He astutely notes that Lutherans were ‘caught between the Scylla of not wanting to distinguish the activities from the essence, and the Charybdis of not wanting to treat the activities as mere extrinsic denominations. Whether or not Lutheran Christology of the majestic kind has anything to add to these opposing medieval accounts thus remains to me a matter for doubt’ (p. 262). Yet what is not at all a matter of doubt is that readers are indebted to Cross's painstaking reading, reflection and research, the result of which illuminates the pathway – oft-mysterious and labyrinthine – toward an augmented understanding of the ontology and theology of the hypostatic union embodied in the eucharist. Cross has shown convincingly that these putatively esoteric and arcane theological debates of the sixteenth-century still have deep resonance in the way the identity and economy of Christ, particularly through the eucharist, is comprehended and participated.