Looking beyond theological narratives and offering a sociological, economic, and historical examination of the spread of earliest Christianity, James Crossley presents a thoroughly secular and causal explanation for why the once law-observant movement within Judaism became the beginnings of a new religion. First analyzing the historiography of the New Testament and stressing the problematic omission of a social scientific account, Crossley applies a socioeconomic lens to the rise of the Jesus movement and the centrality of sinners to his mission. Using macrosociological approaches, he explains how Jesus' Jewish teachings sparked the shift toward a gentile religion and an international monotheistic trend. Finally, using approaches from conversion studies, he provides a sociohistorical explanation for the rise of the Pauline mission.