The religious revolution of late antiquity and its intertwined religious history are reflected in a broad array of new forms of religious belief and practice, of which Christianity is only the most perceptible one. It is represented in the passage from polytheistic systems to monotheistic and dualist ones, as well as in the move from rituals centred upon sacrifices in temples to rituals established upon scriptures, in churches, synagogues, or mosques. This double dynamism of beliefs and rituals sheds light on the transformations of religious ethos. Guy G. Stroumsa’s two-part volume reflects this double argument. The essays all focus on central aspects, such as in Part I on mental aspects of religion in the Roman Empire, as expressed in early Christian texts and traditions, and in Part II on religious communication across the empire’s cultures and communities.