The first chapter outlines the book’s central theoretical questions and contributions, emphasizing the importance of boundaries and authorities. These boundaries—politics, gender, sex, and the Internet—help to establish the distinctions from the outside world that ground each school’s identity. That identity is then experienced as real through certain practices, and those practices are maintained via certain “external authorities,” especially scripture, prayer, and science. These external authorities are at once practices themselves and the institutionalization (what some might call reification) of these practices, things that people do (read the Bible, pray, invoke science) but at the same time, things that seem to exist above and beyond any individual person, and seemingly with the ability to act on people themselves. The chapter ends by describing the four high schools—two Sunni Muslim and two Evangelical Protestant—where the author conducted fieldwork.