This study is the published version of Christine Müehlenkamp's dissertation in theology. Its title translates as Not like the heathen: studies on the boundary between Christian community and pagan society in the pre-Constantinian period. It primarily draws on the writings of Tertullian, Clement and Cyprian, along with the Didache, the Traditio Apostolica, and the Synods of Elvira, Arles and Ankyra. Almost all of the secondary literature engaged with is German and/or continental. Mühlenkamp's basic goal is to assess how Christians differentiated themselves from pagans through their ethical behaviour (Lebensführung), seeing this as a practical application of Christian identity. She sets out to define where the boundary between Christianity and paganism was (which ethical mores were key) and what that boundary consisted of (whether it is essentially religious, ethical, social or cultural). She also pursues the question of how sharp the boundary was. The study concludes that the key ethical mores differentiating pagans from Christians were idolatry and sexual immorality, with baptism serving as the defining act of Christian identity. Mühlenkamp identifies four types of differentiation, namely strict rigorism (Tertullian), separatism with the option of practical compromises, Clement's interpretation of Christian life as a good life within an aristocratic framework, and pragmatic integration as reflected in the ecclesial canons. The boundary was thus of an ethical nature, and Mühlenkamp concludes that it was a definite one, recognised by outsiders, despite inter-Christian debate about exactly how strictly it should be maintained. Mühlenkamp's conclusion is that there was both a hard boundary when it came to cultic and religious issues, and a softer and more inclusive boundary when it came to ethical issues, motivated not least by the desire of Christian communities to make converts. Mühlenkamp has produced a study of ethical instruction to Christians which fits squarely within the German theological tradition in its approach to early Christianity, sharing not only its lack of interest in larger questions of theory and methodology, but also its philological rigour and its heroic thoroughness in attention to detail. Had her stated aim been to provide an accurate and detailed account of ethical instruction in a particular period, this book would have fully achieved its goal. However, there is an absence of reference to the last six decades of critical theory, especially on issues of power, identity and institutions, which could have led to a more nuanced assessment of the social differentiation of pre-Constantinian Christian communities.