One of the core interests of sociology is the study of social stratification—the inequalities in income, power, and prestige. Few persons would care about such inequalities if the poor, powerless, and despised were as happy and fulfilled as the wealthy, powerful, and admired. Sociology springs from humanistic empathy and concern as much as from scholarly and scientific curiosity. This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book highlights two distinctive elements of the sociological approach: looking for gradations in distress rather than diagnosing mental illness, and interviewing people in the community rather than experimenting in laboratories. It describes psychological distress and the ways of measuring its gradations. The book talks about experimental studies of distress. The essence of an experiment is that a researcher manipulates a hypothesized cause and randomly assigns subjects to different levels of exposure.