This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book explains Erving Goffman’s status as a sociological theorist and the significance of his oeuvre were quite controversial during his lifetime. Due to the clarity of his language, which is unencumbered by theoretical jargon, Goffman’s writing is intuitively approachable and his vivid examples are easy to comprehend. His depictions and insights are frequently borne out directly on the evidence of the reader’s own observations and confirmed in everyday experience—with the often surprising effect that the familiar suddenly takes on a different aspect. However, it is the system of Goffman’s thought, that brought him even closer to the new sociology of knowledge. This system operates precisely within the double aspect of societal reality so significant for the sociology of knowledge, and in addition to the stability, security, and reliability of social realities, Goffman also recognizes their unpredictability, vulnerability, and provisional nature.