Cavan Concannon uses network theory to investigate the epistles of the little known Dionysius, bishop of Corinth (c. 170), highly redacted or referred to by Eusebius of Caesarea (Historia ecclesiastica 2.25.8; 3.4.10; 4.21.1; 4.23.1–3,6–8,12; 23.13). He tries to show through Dionysios's correspondence that early Christianity ‘might be conceptualized as a series of networks that occasionally interacted with one another and that emerged, proliferated, grew, and decomposed’ (p. 209). The letters, sent as far as away as ‘collectives' (which, in keeping with the network metaphor, Concannon prefers to ‘church’) in Nicomedia, in Amastris on the southern shore of the Black Sea, and Rome in the West, as well as nearer to home in Sparta, Athens and Crete, reveal the deposits of a well-connected and influential early Christian who has otherwise disappeared from history. Concannon's study considers the energy, cost and personal contacts that made Dionysios's communication possible and in doing so promotes a history of nascent Christianity that makes a cautionary tale of linear accounts of (proto)orthodoxy and heresy in the Early Church as well as models early Christianity centred on notions of varieties or trajectories of belief. One ought rather to seek a description of Christian origins that captures its dynamic ‘processes and syntheses, coagulations and decompositions, that precede the emergence of fixed identities and categories' (p. 40). Network theory, specifically the kind promoted in the writings of Gilles Deleuze, Felix Guattari and Bruno Latour, furnishes Concannon with the diagnostic methods to write his post-mortem report.

Concannon divides his study into six chapters, followed by an appendix that presents Eusebius' Greek fragments with a facing English translation. A poorly catalogued subject-author index limits engagement with Concannon's theorisation of his analytical model and is a regrettable obstacle to enjoying his insightful engagement with other scholars. The first chapter (pp. 25–65), outlines Concannon's eclectic, oft-named ‘assemblage approach’ (pp. 6, 23, 26, 34) that seeks to trace the ‘lines of connectivity that knit early Christians together’ (p. 40). Rather than doctrines and institutions, Concannon aims to describe the connectivity that Dionysius operationalised through his letters. With the help of the Stanford University ORBIS mapping platform (pp. 61–4, 78–81), which shows the travel routes, distances and time, as well as the costs involved in moving from one point to another in the Roman Empire, Concannon measures the challenges facing Dionysius in networking with far-flung communities. The ontological theorisation of Deleuze, Guatarri and Latour invites attention to the roads and seas, boats and wind currents, money and patrons that were as much a crucial part of Dionysios's network as were the ideas that he shared or rejected amongst his contacts. His explication of the theoretical apparatus of these theoreticians is admirable, as is his use of them to insist upon the dynamism of the lived world of the past and present, but it is not always clear how much they add to Concannon's own insightful and straightforward analysis of travel and communication in the ancient world and the dynamism of identities they brought with them. The succeeding chapters deploy the method. Chapter ii (pp. 66–87), drawing insightfully on the Mediterraneanism of Braudel and his contemporary interlocutors, locates Dionysios in the world of the thickly networked and prosperous trade hub Corinth and seeks to understand the ways in which his urban location helped the bishop to exploit pre-existing Mediterranean patterns to nurture contacts with widely distributed communities. Chapters iii–vi examine the networks along which Dionysios's letters travelled and their points of contact with ecclesial, economic and theological concerns. The third and fourth chapters (pp. 88–121, 122–54) focus on Dionysios's correspondence, his two letters to Sparta and Athens in Achaia and to Nicomedia and Amastris in Pontus-Bithynia. Network analysis in the case of Dionysios's interventions in Sparta and Athens considers political turmoil in the Antonine Sparta (pp. 89–91) and ‘shared apostolic lineages, a common provincial geography, and the processes of exchanging letters' (p. 96), an account that makes facile Bauer's account of Dionysios as the bishop of Rome's lackey delegated to expand his beachhead of ‘orthodoxy’ in Corinth to the rest of ‘heretical’ Greece. Basing his argument on the fact that Dionysius wrote to the Nicomedians to refute Marcion, Concannon contends, eisegetically and circumstantially, that the intervention in Amastris must similarly have been anti-Marcionite. More compelling is his observation that the letters refashioned the trade networks connecting Corinth with Nicomedia and Amastris into channels for religious communication, a metamorphosis remarkable because of the cost and energy of its undertaking. In chapter iv (pp. 122–54), Concannon turns to Eusebius' report of Dionysios's letter to Gortyna and Knossos, already networked rival cities on Crete, as well as the response of Pinytus, the bishop of Knossos, to the Corinthian bishop. Concannon detects opposition to Marcionism in Gortyna and observes, in correspondence with Knossos, the diplomacy that accompanied early Christian networking, specifically in disagreement, as between the moderate Dionysios and the more rigorist Pinytus, over chastity and marriage. The fifth and sixth chapters (pp. 155–77, 178–208) centre on Dionysios's letter requesting financial relief from Soter, the bishop of Rome, a city with which Corinth was heavily networked. Here Concannon ‘conjures' a ‘ghost object’, namely ‘a little historical imagination’ (p. 156) to imagine the appeal motivated by the arrival of the Antonine plague, of which there is no mention in the letter. Concannon ‘want[s] to conjure a crisis, some hypothetical emergency to reactivate Corinthian assemblages that might allow us to see the potentialities within the landscape of Corinth as Dionyios would have known it’ (p. 156). His aim is not to engage in make-believe, but to suggest a heuristic model for a relief request, the negotiations such an appeal would require and the kinds of networks of house church assemblies in Rome that Soter would have needed to activate to be successful. For his part, Dionysios appeals to a pre-existing network with Rome, reminding Soter that the Corinthians read Clement's letter to them regularly. The conclusion (pp. 209–32) considers the efforts of Dionysios to manage his letters; when alive he condemned people for doctoring them or writing falsely in his name, and as a consequence gathered his epistles into a single collection. Most of the (little) scholarship dedicated to Dionysios considers the contents of the collections and the motivations for creating it, which Concannon summarises, but it is puzzling, given the project as a whole, that he does not consider – apart from Eusebius' account – Dionysios's afterlife in creating imagined and real networks, by referring to other letter collections (such as Ignatius' Middle and Long Recensions) that might have helped to construct or to maintain contacts. Concannon does, however, consider the absence of Dionysios in Asia Minor, which he uses to consider the existence of contemporary Christian networks coming into being and passing away independently of one another, and which possibly, because of their bounded nature, simply excluded participants like Dionysios (pp. 225–7). Concannon's study illustrates the potential of network theory for conceptualising a history of the Early Church that moves beyond the balkanising categories of orthodoxy and heresy to tell a more complex and effervescent story of Christian origins.