If the so-called secular age arrived long ago, the historiography of the secular has lagged behind. Only very recently have historians of Germany begun to treat the secular as something other than the mere absence of religion. In Secularism and Religion in Nineteenth-Century Germany (2014), Todd Weir made the case for studying secularism as a movement in its own right, explaining that secularists were motivated not just by opposition to organized religion but also by support for a scientific worldview and an ethical system based on the balance of individual and communal needs. He even went so far as to claim that secularists constituted a fourth confession alongside Catholics, Protestants, and Jews. These groups already have received extensive treatment in the rich historiography of religion in the Kaiserreich since the 1980s, pioneered by David Blackbourn, Jonathan Sperber, and Margaret Lavinia Anderson, and taken up by younger scholars such as Manuel Borutta, Michael Gross, and Ari Joskowicz. Collectively, these scholars exposed the long shadow cast by Kaiserreich-era scholars working on the history of religion, evident in neglect of and even contempt for Catholicism and an unthinking embrace of liberal Protestant (and Jewish) norms.

The first essay in this volume, by Wolfgang Knöbl, echoes their findings. He shows that Max Weber shared the general liberal distaste for the working-class, feminine, and international aspects of popular piety and endorsed the notion of religion as a private matter, thus facilitating the secularity of the public sphere.

In a fine introduction, the editor, Rebekka Habermas, explains the value of exploring the secular alongside the religious aspects of the Kaiserreich. Drawing on Talal Asad's Formations of the Secular (2003), she rejects the notion of a fixed boundary between the religious and the secular, arguing that any such boundary was subject to subtle shifts across time and space. By implication, she challenges the assumption underlying the secularization thesis and indeed its opposite—claims of religious revitalization—that one can measure religiosity. Instead of the rise or decline of religiosity, she argues that the Kaiserreich was marked most of all by intense negotiations of that boundary between the religious and the secular. She considers Weir's examination of secularism too limited and calls for the inclusion of figures who did not belong to organized secularism but who nonetheless protested against religion in public life. For instance, she cites occasional contributors to the popular family weekly, Die Gartenlaube, who railed against exorcisms and miracles, or glorified the occult and theosophy. Noting that such stances were not necessarily incompatible with religious convictions, she recommends the useful notion of “situative secularity” (118), an echo of Till van Rahden's concept of situative ethnicity, and suggests that it was perhaps connected to particular moments in a person's life cycle.

Habermas also draws attention to the importance of gender in shaping the boundary between the religious and the secular. She proposes the “masculinization of the secular” (121) as a counterpoint to the thesis of the “feminization of the religious” in the nineteenth century. Although the prominence of Helene Stoecker in the Monist League and women in Berlin's Free Religious Congregations shows that secularism was not a male preserve, secularists outside the organized movement could well have been overwhelmingly male. Certainly, Habermas is correct in identifying the strong overlap between secular values and male, middle-class attributes such as rationality and independence, and the irony of their highly emotional rhetoric.

This volume is particularly innovative in its commitment to transnational approaches, highlighted in its subtitle. Habermas notes her intellectual debt to Indian historiography, which pioneered the study of the history of the secular. Relinde Meiwes reminds us that the female religious developed their own transnational networks to rival those of their male counterparts. Carolin Kosuch points to the influence of Jewish mysticism from Lviv in Habsburg Poland, transmitted by Martin Buber, on anarchists Gustav Landauer and Erich Mühsam. Paul Michael Kurtz documents the importance of Palestine for German Protestant theologians. Contributors regularly compare events in Germany with other parts of Europe and North America. Lucian Hölscher, for instance, notes that the term secularization, meaning a decline in religiosity, entered the German language only around 1900, some fifty years after English, although institutions such as universities, clubs, and journals in Germany were generally more secular than those in England or North America.

The activities of missionaries offer a particularly interesting focus for the discussion of the boundary between the religious and the secular. Essays by Meiwes and by Richard Hölzl and Karolin Wetjen remind us that missionaries did not admit to any division between the secular and the religious. Although they served the state in taking responsibility for much of education, health care, and social work in the colonies, they saw this work as fulfilling a religious purpose, often in opposition to the exploitative and violent approach of many colonists and bureaucrats. Yet in deciding which indigenous people were worthy of conversion, missionaries were often forced to decide on the boundary between what was essential to religion and what could be accepted in certain circumstances.

The essay by Hölzl and Wetjen shows that Protestant and Catholic missionaries in German East Africa had to decide which indigenous traditions were adiophora, compatible with a Christian lifestyle, and which were not. Although male circumcision was deemed such, the continued practice of polygamy was normally, if not universally, considered an obstacle to conversion. Such negotiations between the religious and the secular were, however, not purely a matter of theology. The authors show that the pressure to gain converts while also avoiding criticisms of heterodoxy from rival Christian missionaries led to clever circumventions, such as secret or emergency conversions.

The editor can rest her case that the boundary between the religious and the secular is a particularly promising site for investigating the Kaiserreich. This volume reveals the vibrancy of debates around religion, the gendered character of secularism, and the pivotal role of missionaries in defining the limits of the orthodox, all of which were informed by transnational contexts.