This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. Herbert Marcuse was certainly the most famous member of the so-called Frankfurt School, particularly in the United States, but his thought may be the least understood of any of the Frankfurt critical theorists. Marcuses contemporary reputation, which is still largely determined by his active engagement in the protest movements of the 1960s, tends to conceal the fact that he spent over five decades engaged in critical theoretical work. The mere mention of Marcuses name today often provokes an array of responses that reveal more about the respondents attitudes toward the 1960s than about Marcuse or his critical theory. These responses range from wistful smiles and an open admission of a nostalgic yearning for the 1960s, when radical social change still seemed possible, to heated denunciations of Marcuse as the intellectual agent behind a vaguely Marxist program of political correctness.