Irish historians have long recognized the importance of early modern migration, outward and inward, although the subject has sometimes been treated as ancillary to the main business of conflict between “native and newcomer” (316). Tadhg Ó hAnnracháin's latest book therefore makes an especially significant contribution by drawing on an incredible body of research to illustrate the centrality of “mobility” to “religious identity and practice” (3) in the period from ca. 1580 to 1685. Indeed, the author's treatment of mobility ensures that the book offers an important case study beyond its Irish subject matter.

The first part of the book examines the manner in which mobility influenced the development of the three main confessional groups in Ireland: Catholics, Church of Ireland Protestants, and Dissenting Protestants. The first three chapters cover reasonably well-known territory (not least thanks to the author's groundbreaking earlier work): the influence of migration in shaping clerical and lay Catholics. This involves detailed discussion of a number of themes: the continental colleges (quite correctly described as “a haphazard and untidy web” of institutions [55]), the formation of bishops and clergy abroad, their impact on Church reform and reconstruction at home, and the European migration of what the author terms “secular Catholics.”

Chapter 4 is devoted to the Church of Ireland. It shows in detail the centrality of mobility, including migration, to the experience of the state Church, with a strong emphasis on the careers of a number of key bishops, although lay Protestants also merit significant attention. Chapter 5 necessarily adopts a slightly different chronology to chart the impact of migration and mobility on Protestant dissent in Ireland, beginning in the 1620s before the establishment of the first Presbytery in 1642. The chapter tracks movement between Scotland and Ireland, and discusses mobility more generally, not only for Presbyterians but also for smaller dissenting groups.

The second part of the book turns to images and practices of mobility, as well as the ways in which mobility, and especially migration, shaped confessional identity. Chapter 6 offers an original examination of the use of “figurative images of mobility,” such as the Exodus story, which were employed across confessional groups in Ireland. Chapter 7 is equally revealing: a study of how the practice of mobility expressed identity as “enacted through performativity” (223). Ó hAnnracháin assesses processions, ceremonies, devotions, pilgrimages (international and insular), as well as the movement of confessional leaders and congregations. The last two chapters turn to the knotty problem of how migration impacted the development of confessional identity. The author tackles the subject through a number of key writers and offers fascinating readings of Catholic and Protestant figures. In his examination of the Catholic writers Peter Lombard, David Rothe, and Philip O'Sullivan Beare, Ó hAnnracháin underlines one of the central contentions of the book: that mobility—here, migration to Continental Europe—is essential to understanding identity formation. This connection is then extended to the other confessions in Ireland, through a striking examination of a series of Protestant texts “strongly marked by the experience of immigration and the strong pull of English and Scottish identities and affiliations which they continued to feel” (315).

The conclusion merits specific note for its thought-provoking observations on, inter alia, viewing Catholics as confessional migrants rather than religious refugees, and the need for further work on women and mobility in early modern Ireland (a theme raised throughout the book). Confessionalism and Mobility is both innovative and important in a number of ways. First, while scholars (including Ó hAnnracháin) have devoted significant attention to the manner in which migration shaped early modern Irish Catholicism, Ó hAnnracháin breaks new ground in his multiconfessional approach: all of the island's confessions were shaped by mobility in significant, sometimes similar, ways. Second, Ó hAnnracháin deploys a sophisticated methodology, drawing on work in the social sciences to highlight a broad range of mobilities, from the everyday to the migratory. Indeed, the emphasis here on the impact of everyday mobility is especially noteworthy: historians will not be surprised to read about a subject such as Catholic pilgrimage, but Ó hAnnracháin's thoughts on the importance of journeys to and from more mundane religious services are illuminating. Third, the book is very strong on comparative possibilities, as one would expect from the author of Catholic Europe, 1592–1648: Centre and Peripheries (2015). Fourth, and crucially, by placing mobility—and migration—at the heart of the story, Ó hAnnracháin shows that it is no longer possible to write early modern Irish history as an essentially island story, with the migrants tacked on.

This is a significant book, essential reading for historians of Ireland, but one with ramifications well beyond the island. Indeed, while Ó hAnnracháin does not make the point, it is a book with far-reaching implications beyond the study of history.