This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book addresses an unresolved crisis about child sexual abuse (CSA), which has two aspects. The first is that people disagree about whether it is an overstated or understated public policy challenge. Second, people disagree about what to do about it, especially in the face of an increase in online offending in the wake of the mass availability of the Internet. The book is concerned with CSA in recent times and one of its aims is to put its topic into historical context. It is concerned only with modern history because the views about adult–child sexual contact have changed so quickly and dramatically over the past 50 years. A naive realist or positivist stance in the first grouping may simply be taking social norms for granted and assume that adult–child sexual contact is self-evidently wrong and harmful.