In this monograph, Mary E. Sommar surveys ecclesiastical attitudes about slavery and the regulations applied to unfree dependents of the churches, from the ancient New Testament period through the thirteenth century. Sommar's central purpose is to correct “popular” claims that Christian teachings and the church “have always condemned slavery and were instrumental in its eventual abolition in Western society” (3). Instead, each of the six main chapters demonstrates that ecclesiastical leaders accepted the social and economic reality of slavery throughout this period and made no institutional effort to end it; in fact, the Roman Catholic Church did not officially condemn slavery until the 1960s (3–4, 253–254). Individual churches and bishops consistently were masters to enslaved persons, which were considered part of the res ecclesiae, or property of the church, which like land and other valuable objects could not be alienated.

To avoid teleological conclusions and conflating historical contexts, Sommar takes a chronological and geographic approach, covering territories from the Anatolian Peninsula to North Africa and Iberia, with an emphasis on western Europe (1, 6). Sommar's broad scope is balanced by the narrow focus of her questions, which center on the development of regulations for the slaves owned by churches, servi ecclesiarum, and to a lesser extent, ecclesiastical leaders’ views on being slaveowners. To answer these questions, Sommar relies heavily on local and ecumenical canonical sources, along with ecclesiastical letters, sermons, charters, royal proclamations, secular law codes, and church donation records and deeds (6–7, 158–165).

Sommar begins by contextualizing the evidence for New Testament attitudes about slavery within ancient Greco-Roman and Jewish traditions to show that rather than condemn slavery, early Christian communities accepted that servile status was part of the social order. Christian leaders frequently owned slaves and did not develop regulations outside of secular legal custom, which mandated that slaves should obey their masters along with vague protections against their mistreatment (36–37). Next, Sommar demonstrates that like secular lords, bishops with sufficient means continued to own slaves in the first through fourth centuries, and there was nothing exceptional about Christian moral teachings on slavery. Similar to the Stoics, some ecclesiastical masters viewed those they enslaved with humanity, particularly in the context of Christian worship, but like their pagan neighbors they largely regarded slaves as possessions, and accepted that torture was necessary to obtain legal evidence from enslaved witnesses (49, 56, 61–63). With Constantine's support, churches became corporate owners of significant estates and their slaves, making the bishops’ administration of the res ecclesiae increasingly complex. More frequent church councils produced canons throughout the empire insisting that the res ecclesiae —including its servi—be preserved and kept separate from the bishops’ personal property (64–76). Freeing slaves was understood as a way to express “holy poverty,” but this was not a general rejection of slavery, since it was viewed as God's punishment for human sin; indeed, there was greater concern for maintaining the church's patrimony (65–67, 102–103). Constantine also granted bishops the ability to free slaves in a church ceremony, manumissio in ecclesia, and ecclesiastical leaders built on this to establish patronage ties between these liberti and the churches where they gained their freedom (80–83).

Chapter 5 examines the period after the collapse of the western Roman Empire through brief surveys of ecclesiastical slavery within the Germanic successor kingdoms and Justinian's eastern Empire, with an emphasis on the Franks and Visigoths. Sommar concludes that although there were variations—such as the Frank's concern with social rankings and having proper penalties for different status groups, and the Visigoths using harsher punishments due to their apparent contempt for the enslaved—there was little difference in how the regions interpreted Roman legal traditions (144, 148–149, 152–153, 242–243). Lay and ecclesiastical masters “exercised dominium over their servile dependents” according to similar regulations (153). However, it was in this period that laws first appeared in both regions, which would have enduring significance for canon law and the status of liberti ecclesiae, manumitted slaves of the church. Specifically, Frankish and Visigothic councils ruled that since ecclesiastical property could never be alienated, unlike their secular counterparts, most liberti ecclesiae and their descendants would not achieve complete freedom since they were tied to the church in perpetuity (144–153). The chapter on the Carolingians, which includes the British Isles as it “began to engage more deeply with the mainstream church” (6, 183–189), outlines how conciliar rulings on the church's unfree workers through the ninth century remained focused on the inalienability of ecclesiastical resources and preventing the misappropriation of the res ecclesiae, including its servi. Carolingian interest in a secure realm through episcopal alliances meant that there was royal support for these mandates, except when kings required ecclesiastical resources and there were sufficient assets to continue to serve the poor (167–171).

Chapter 7 shows that even with the changing social, political, and economic circumstances that made the differences between free and unfree labor largely “irrelevant” by the thirteenth century, ecclesiastical law, as evidenced by Gratian's Decretum and Gregory IX's Decretals, remained largely unchanged with regard to servi ecclesiarum (238). Although scholars were beginning to acknowledge the humanity of servile populations, the continued emphasis on the inalienability of church property meant that liberti ecclesiae could not escape obligations to the church, particularly when they sought to be ordained. In chapter 8, Sommar concludes with a brief overview of canon law after the thirteenth century, including within the Atlantic World context, through the late twentieth century (246–254).

As Sommar admits, this study does not include “breakthrough theories” and her conclusions will not surprise scholars familiar with the history of servi ecclesiarum (240); regional specialists certainly will note gaps in the historiographical engagement. Yet, the book is significant for establishing for students and general readers that throughout the periods and regions covered, churches and the clergy consistently owned enslaved individuals and families, and developed methods to create enduring ties with those they freed and their descendants. Her frequent summaries and concise explanations of historical developments and figures make the complex subject matter accessible, and each chapter is suitable as a starting point for more in-depth discussions.