The editors make clear from the outset that their goal is neither to produce a historical survey nor a devotional celebration, but to engage with the Council of Nicaea as a living and contested phenomenon – one whose meaning and legacy remain genuinely open questions for historians, theologians, and church leaders alike. The book is divided into five parts – Nicaean Theologies, Historical Memory, Conciliarity, Ecumenical Implications, and The Future of Nicaea. Given the total of twenty-one articles, it seems more useful to focus here on a selection of contributions, discussing one or more essays from each section.

One achievement of this book is that, in its account of Nicaea, it does not neglect the theological antecedents of the preceding centuries – an aspect often overlooked in scholarship. John Behr examines the Council of Antioch (268), where the debate between Paul of Samosata and Malchion offers important insights for shaping the conceptual map of fourth-century theology. In addition, the article highlights the close interplay between Trinitarian theology and Christology, as well as between the third and fourth centuries. Bogdan Bucur addresses theophanies – that is, pre-incarnate manifestations of the eternal Son in the Old Testament – and shows the extent to which different Trinitarian theologies shape their interpretation. According to Eusebius of Caesarea, the subject of these manifestations is the ‘second God’; for Marcellus of Ancyra, by contrast, it is the proper divine word of the Father – understood as a dynamis – that appears in the Old Testament; and Athanasius of Alexandria employs theophanies to demonstrate that the Son is consubstantial with the Father. Finally, the article argues that, with Augustine, this rich theological tradition underwent a decisive shift and ceased to play a central role.

Emanuel Fiano proposes a new conceptual approach to Nicaea. Drawing on the theory of Pierre Legendre, he argues that Christian theology and Roman law cannot be understood as separate domains. Within this framework, Fiano maintains that, in late antiquity, Nicene theology functions as the ultimate ground of legitimacy for the law. Accordingly, the declaration ‘We believe’ does not merely express articles of faith but constitutes a collective subject defined by a ‘dogmatic’ reference. In light of Legendre’s theoretical framework, Fiano further argues that Christian theologians developed a system of interpretation of the Creed anchored in Scripture as the foundational and authoritative text, and articulated the ‘patristic argument’, a corpus of trustworthy opinions of earlier theologians gathered in support of doctrinal claims. John Chryssavgis offers a provocative contribution that critically assesses the direction the Church took during the Constantinian shift: ‘I cannot help but feel that the Council of Nicaea was a formidable gift from the emperor to the newly adopted and formalized Christian community but at the same time an opportunity unambiguously squandered by the bishops in attendance’ (p. 112). Rather than engaging with the transformation of secular society, the church leaders opted for institutional consolidation, of which the twenty canons of Nicaea provide a clear example.

Leslie Baynes approaches the Council of Nicaea by comparing it with the Council of Jerusalem. Both assemblies are regarded as foundational for the Christian tradition, and the records of each are problematic. The article offers a careful analysis of the two accounts of the Council of Jerusalem, including patristic testimonies and textual variants. Baynes then examines selected accounts of Nicaea, namely the Life of Constantine and Eusebius of Caesarea’s letter to his church; the study could have addressed the testimonies of Athanasius (decr. 19–20) and Eustathius (fr. 79). The comparison successfully identifies a pattern: the narratives of both councils emphasize unanimity and minimize difference; in doing so, the article highlights the broader dynamics of retrospective retellings of foundational events.

Edward Siecienski addresses the question of doctrinal development, a crucial issue in modern Christian theology. Drawing on Jaroslav Pelikan and John Courtney Murray, the article argues that the acceptance of the Nicene homoousios implies that Christian doctrine can be legitimately articulated in a language not found in Scripture. Siecienski then outlines different positions on doctrinal development. In his view, Catholics understand it as an organic process; Protestants regard it as a clarification of biblical doctrine rather than a development; whereas Orthodoxy maintains that strict doctrinal development is not acceptable. The article problematizes the concept of doctrinal development and concludes that ‘the Orthodox rejection of doctrinal development cannot yet be taken as a given’ (p. 255). Christophe Chalamet addresses the question of what role the Nicene Creed might play in the future of Christianity. He surveys the complex and problematic reception of Nicaea within modern Protestantism, from the Reformation to the present, and proposes a constructive account of how the Nicene Creed might serve the Church in the coming decades. In light of the path opened by Karl Barth and David Bentley Hart, Chalamet proposes the category of tradition as a living, forward-oriented reality rather than a static deposit. With this understanding of tradition, the Creed of Nicaea could, in the future, be regarded as a relational reference point within the context of global Christianity, especially in liturgical contexts.

The book reveals both the fruitfulness and the risks inherent in the necessary interaction between historical studies and theological reflection on Nicaea – a constant challenge. Historical studies of Christianity cannot be self-enclosed, just as systematic and ecumenical reflection must take historical research as their point of departure. In summary, these essays successfully demonstrate, in line with the purpose of George Demacopoulos and Aristotle Papanikolaou, ‘how far from being an historic relic or a means to stifle debate within the Christian tradition, Nicaea remains a rich source for discernment and conversation. More importantly, they also indicate that Nicaea will always have something to say about the future of Christianity’ (p. 5).