The nineteenth-century concept of Catholic reunion was not just a restoration of an idealised mythic past wholeness, it had real, practical implications. The rise of secularism and scholarly methods that some perceived as undermining central tenets of the faith, challenged the nineteenth-century Churches. Colonisation of non-Christian territory provided both an opportunity and a challenge to missionary efforts – impeded in part by the divisions between colonising believers, sometimes from the same country. The increased mobility of traders, travellers and opportunity seekers created a pastoral problem. The Protestant Jerusalem bishopric (1841–86) attempted to address both the missionary and pastoral challenges through a joint Prussian-Anglican venture. It failed, and in the process laid bare some of the difficulties for any effort at reunion. Vatican I proved to be an important catalyst for a Catholic reunion project. Opposition to the introduction of new doctrines gave rise to the Old Catholic movement in Germany, Switzerland and the Netherlands. The German church historian Johann Ignaz von Döllinger, a well regarded and vocal opponent of the Vatican decrees, and for many the public face of the Old Catholic cause, seized the opportunity and brought together Old Catholic, Orthodox and Anglican churchmen to organise the Reunion Conferences of 1874 and 1875. Practical benefits were quickly overshadowed by technical theology, such as what to do with the Filioque, and the realisation that the three Churches, which did not know much about each other, had developed very different theologies. Catholics without Rome traces the development and realisation of the Reunion Conferences of 1874–5 which Döllinger organised.

It was the esteem that participants had for Döllinger and their curiosity about the emerging Old Catholics (and how they might influence them) that contributed to Anglican and Orthodox sympathy for the conferences. These factors did not however, prevent their failure. The book argues that, while the conferences held out the promise of a united Catholicism and were sustained by optimism and Döllinger's personal involvement, theological disputes, debates within individual churches and even nationalism posed insurmountable challenges. The Old Catholics and the Orthodox were dubious that Anglicans maintained apostolic succession, and they insisted that Evangelicals must convert. The Orthodox were split between progressives such as Alexander Kireev who argued that there was room for diverse opinion alongside doctrinal unity, and the conservatives such as Alexander Gusev whose absolutist position effectively demanded the conversion of both the Old Catholics and the Anglicans. The conferences were not officially sanctioned, thus Anglican and Orthodox participants had no authority to speak on behalf of their respective Churches. The Old Catholics were not only facilitating the conferences, but at the same time organising themselves into an ecclesial body. All three groups, German (Old Catholic), British (Anglican) and Russian (Orthodox), represented a national Catholicism. The politics of nationalism created additional barriers to achieving the goal of reunion. It gave rise to competition, a jostling for dominance, and a struggle to ensure that one was not overwhelmed or subsumed by the others. There was little enthusiasm for, and no popular movement supporting, the idea of a Catholic reunion project. The conferences, therefore, never broke out of the confines of an academic thought experiment.

The book is loosely organised into four sections. The first four chapters set the stage for the rupture of the Old Catholics from Rome. The second section (chapters v–vii) details the work of organising the Old Catholics, and the role that key figures such as Döllinger played in sparking the sympathy of Orthodox and Anglican observers. The third section delves into the development of the agenda for the conferences, and the behind the scenes correspondence of participants, as well as the reaction ‘back home’ to their reports. The final section analyses why the conferences did not continue after 1875, why they failed to achieve their goal of uniting the three Churches and how, through the dogged efforts of a number of the participants, the Reunion Conferences laid the foundation for ecumenical conversations that continue today.

The book provides a fuller picture of how Döllinger and the Old Catholics struggled to keep all three Churches talking in 1874 and 1875. In the correspondence and debates back and forth between delegations and within their respective confessions, the book draws out the tensions and points of convergence and divergence – even the lengths to which the participants went to be able to report back to their Churches that there was hope of progress. The book introduces a significant amount of primary material from Russian Orthodox sources. It expands on the involvement of familiar Orthodox participants such as the progressive-leaning Kireev, and introduces others such as the conservative Gusev. This fuller account of Orthodox involvement demonstrates that they were substantive participants in the proceedings, and rebalances the narrative about the reunion conferences, making it a three-way dialogue; whereas earlier accounts often emphasise the Old Catholic-Anglican interaction as laying the foundation for their 1931 Bonn Agreement.

This book is also a useful reference point for exploring later Protestant reunion projects such as the Grindelwald Conferences (1894–5). These were organised along similar lines, as an unofficial, almost academic discussion, and like the Reunion Conferences failed to produce the desired outcome. The World's Parliament of Religions (1893), unlike either the Reunion Conferences or the Grindelwald Conferences, was organised alongside a widely publicised popular movement, the Christian Brotherhood. The WPR sought to realise (Protestant) reunion, in an effort to address the challenges of missions and rising scepticism through a mass movement, and a minimalist approach to doctrine. The book provides valuable insights into the context, challenges and motivations for both of these later projects.

The text mentions in passing a few of the more quixotic characters of the reunion story such as Joseph Overbeck, a convert to Orthodoxy, and Frederick Lee, an Anglican priest and eventual convert to Roman Catholicism. Lee was an early organiser of the APUC (Association for the Promotion of the Unity of Christendom), and the founder of the Order of Corporate Reunion. It also mentions, although not by name, Joseph Rene Vilatte who, with the help of the Swiss Old Catholics and the American Episcopalians, organised an Old Catholic mission in 1885 in Wisconsin. Vilatte was heavily influenced by Old Catholic and Orthodox thinking regarding reunion, and although he failed, tried to turn the academic Old Catholic idea into a popular movement in Europe and North America. This work provides important context not only for their stories, but also the relationships characters like Vilatte had with participants at the conferences such as Kireev. These more interesting characters are normally presented as isolated oddities rather than tessera of a mosaic of turn-of-the-century reunion idealism.