Ara Norenzayan, professor of psychology at the University of British Columbia, is one of the leading scientists exploring the evolution of religion. His work combines a broad knowledge in evolutionary science with ingeniously designed experiments in social psychology. Fruitfully cooperating with other young-and-hungry scientists, Norenzayan’s empirical articles have appeared in leading scientific journals, including Science and Psychological Science, and his work has been featured in leading news media worldwide. With Big Gods: How Religion transformed Cooperation and Conflict, Norenzayan offers his synthesis of evolutionary and cognitive studies of religion. The book is a breakthrough, and will undoubtedly influence scientific perspectives on religion and secularism.Let’s start with style: Big Gods is pure empirical science. Norenzayan is not catering to religious or atheistic expectations nor is he dabbling in philosophy or staging fights with colleagues. The most he is disclosing about his personal motivation in exploring religion is his childhood in Beirut, Lebanon. Here, he experienced the social as well as violent potentials of human psychology and religious faith. Instead of following ready-made sets of assumptions and prejudices, he dragged them to the lab for empirical testing until he had a viable, evolutionary picture of religion at hand.Thus, Norenzayan is able to present a more complete, cognitive account of religiosity as a biocultural tool of supernatural monitoring. He argues that religion started as a by-product of human cognitions such as agency detection and mentalizing (building theories of mind), which led to a world enriched by mythological agents such as lingering ancestors, watching spirits and later, gods. As "watched people are nice people“, religiosity evolved into a social tool able to augment in-group cooperation. In order to avoid freeriders, religious networks and groups began to adopt "actions that speak louder than words": Credibility-enhancing displays (CREDs) such as prayers, offerings and costly commandments distinguishing "true believers“ from those paying mere lip-service.Norenzayan’s theses are in accordance with archeological and ethnological findings about the co-evolution of increasingly powerful and moralizing gods with bigger groups and agricultural settlements. At the same time, both sides of the religious coin are becoming visible: While religious believers became enabled to build stronger, bigger, and more competitive communities, they became increasingly intolerant towards outsiders and perceived freeriders. Presenting a range of experiments concerning anti-atheist prejudices, Norenzayan is able to show that non-believers are frequently distrusted even in contemporary settings. Other historical as well as psychological studies are supporting assumptions that religious traditions are able to strengthen both conflict and peace.Up to now, Norenzayan’s works would already have been a more than remarkable supplement to former definitions and theses, but he has still more at hand! In his concluding chapters, fresh empirical findings – some of which have already been discussed on TVOL - on the waning of religious beliefs in secure, wealthy, and educated societies and the subsequent rise of secularism and atheism are presented in detail. In short, Norenzayan is able to show that benevolent and trustworthy "Big Governments“ are able to substitute "Big Gods“ in many ways. "Combined with strong secular institutions that keep the cooperative engines going, existential security is the nemesis of religion“ (p. 186). In a powerful metaphor that is set to be quoted widely, Norenzayan observes that "secular societies climbed the ladder of religion, and then kicked it away.“ (p. 172)Finally, Norenzayan is sincere enough to acknowledge "the secularists‘ Achilles‘ heel“: Religious demography (p. 192). As far as we can see historically, only religious communities have been able to retain fertility rates above replacement levels. Wherever religious beliefs dissolved, family structures followed suit. Thus, future debates and studies might probe into the riddle of human motivation. It seems that we are cognitively inclined to accept commandments (such as joining a community or having costly kids) from mindful agents, but not from mindless principles.Without a doubt, Big Gods is a seminal and outstanding book, rocketing the psychological and evolutionary understanding of faith and secularization to new heights and new questions. I strongly recommend it to anyone interested in human evolution, psychology, and the scientific study of religion.