Abstract:The paper analyzes the relation between religious beliefs, religious participation and social cooperation. In particular, we focus on religions that instill beliefs about the connection between rewards and punishments and social behaviour. We show how religious organizations arise endogenously, analyze their e¤ect on social interactions in society and identify a "spiritual" as well as a "material" payo¤ for being religious. We show that religious groups that are more demanding in their rituals are smaller, more cohesive, and are composed of individuals whose beliefs are more "extreme". We use our framework to analyze the response of individual beliefs and religious membership to correlated shocks in society, such as natural disasters or periods of prosperity.1 Department of Economics, LSE. Email: g.levy1@lse.ac.uk; r.razin@lse.ac.uk. We thank Stephen Hansen for valuable research assistance, and the editor of this journal and two anonymous referees for helpful comments.The ESRC (grant number RES-000-22-1856) and the ERC (grant number 210385) provided …nancial support.