"Critical theory" is used to refer to the diverse body of work produced by members and associates of the Frankfurt Institute for Social Research after Max Horkheimer became its director in 1930. The first generation of what came to be called the Frankfurt school included, in addition to Horkheimer, such prominent figures as Theodor Adorno, Herbert Marcuse, Walter Benjamin, Erich Fromm, Leo Löwenthal, Franz Neumann, Otto Kirchheimer, and Frederick Pollock. The most influential members of the second generation are Jürgen Habermas, Karl-Otto Apel, and Albrecht Wellmer. As the variety of backgrounds and interests might suggest, critical social theory was conceived as a multidisciplinary program linking philosophy to history and the human sciences in a kind of "philosophically oriented social inquiry," as Horkheimer put it. Though very strongly influenced by Immanuel Kant and neo-Kantianism, Georg Wilhelm Friedrich Hegel and German idealism, Max Weber and Sigmund Freud...