This book explores the question of ideology in the theory of Louis Althusser. At its core are the influences from psychoanalytic concepts, particularly from the Lacanian school. "People have always had false notions about themselves, about what they are or should be." In 1845, Marx and Engels provided an elaboration of the concept of ideology in the German Ideology, but they lacked a language to adequately describe this phenomenon. In 1963, Althusser seems to have found this language in Lacanian psychoanalysis, which forms the basis for Althusser's theory. Even in For Marx, the treatment of the concept of ideology becomes a topic. Particularly, the concept of overdetermination represents a way out of theoretical deadlocks for Althusser. This endeavor is supported by the thesis of the decentered subject.