When Norenzayan became a student of psychology in 1994, four years after his family had moved from Lebanon to America, he was excited to study the effect of religion on human psychology. “I remember opening textbook after textbook and turning to the index and looking for the word ‘religion,’ ” he told me, “Again and again the very word wouldn’t be listed. This was shocking. How could psychology be the science of human behavior and have nothing to say about religion? Where I grew up you’d have to be in a coma not to notice the importance of religion on how people perceive themselves and the world around them.”

Norenzayan became interested in how certain religious beliefs, handed down through generations, may have shaped human psychology to make possible the creation of large-scale societies. He has suggested that there may be a connection between the growth of religions that believe in “morally concerned deities”—that is, a god or gods who care if people are good or bad—and the evolution of large cities and nations. To be cooperative in large groups of relative strangers, in other words, might have required the shared belief that an all-powerful being was forever watching over your shoulder.