This introduction presents an overview of the key concepts covered in the subsequent chapters of this book. The book gives some indication of the extent to which a theory of toleration can be useful by considering the many—many—sorts of things that can be tolerated. It discusses methods of toleration. The book looks at the normative limits of liberal toleration. It aims to show why toleration, with normative limits set by the harm principle, is valuable. The book considers the normative limits of toleration of what goes on in families. Individuals, families, and cultural groups all exist in the international arena. The book discusses general defenses of toleration, including an argument using economics of religion and another argument from economics—this time from David Ricardo—that supports the view that extensive toleration within society is valuable. Historically, religion and religious practices were the main things considered by those discussing toleration.