Jörg Rüpke is one of the most original and influential scholars of Roman religion of the past half-century, and in this compact volume he offers a theory of the evolution of religions in the Roman Empire which will be equally interesting to students of early Christianity, Roman historians and historians of Roman Judaism. Starting from the assumption that religion is closely interwoven with multiple life practices, the book examines how the evolution of the Roman Empire affected religion and vice-versa. Rüpke argues that the empire saw a decisive change, not so much in the number or content of cults as in the concept of religion and the social locus of religious practices and beliefs. From being much concerned with creating the political identities of individuals and groups and addressing the contingencies of life (illness, death, uncertainty), religion ‘came to embrace the entire context of human life, becoming a medium for the formulation of group identities, and for political legitimation’ (p. 2). One of the consequences of this evolution was to facilitate the spread, and ultimately the success, of Christianity. Through a sophisticated mixture of theoretical approaches and detailed case studies, Rüpke explores themes such as globalisation and regionalisation in imperial religions, the media and vectors of the spread of religion, individual creativity, religious competition, pluralism and apologetic. He discusses the role of Roman ideas about natural law and universal human values in the development of religious thinking, and investigates the increasing significance of modes of association that sat between the public and private spheres. One of Rüpke's strengths as a historian is that he avoids the social-functionalist explanations of religion into which historians of Greek and Roman religions tend to lapse all too readily, and one of the many significant strands of argument in this book concerns imperial cult. Rüpke argues (building on the work of Simon Price) that imperial cult did not simply work to legitimate political power or render that power tolerable by expressing it through traditional rituals. Rather, it maintained the presence of the emperor throughout the empire and, by that means, contributed to the construction of the empire's reality. At the same time, Rüpke challenges the widespread assumption that emperors consciously exported imperial (or any other) cult. Cults were more readily carried and transplanted, for instance, by armies and patronage networks. Few scholars, if any, are as well equipped as Rüpke to discuss both theoretical approaches to the study of religions and the specifics of Roman and early Christian religiosities, both religious ideas and imperial practices. This book ranges effortlessly across all those fields and offers that rare thing: a conceptually challenging and stimulating study that does justice to the complexity of a vast range of evidence. It should be required reading for scholars of Roman religions, early Christianity and Roman Judaism alike.