In his 1964 "One-Dimensional Man: Studies in the Ideology of Advanced Industrial Society" Neo-Marxist philosopher Herbert Marcuse (of the Frankfurt School) describes the state of society under capitalism. Marcuse introduces the concept of the "one dimensional man" as someone who is subjected to a new kind of totalitarianism in the form of consumerist and technological capitalism. Rationalism for Marcuse is a form of oppression which denies the possibility of change.
Marxism traditionally relied on discontent which arises from internal conflict as the motor for historical change. The problem with 20th century capitalism, according to Marcuse, is that conflicts concealed my mass consumer society in a manner which precludes change. We are a type of "blissful slaves", willingly obeying a system which keep us distractedly entertained and numbingly sated. A man under capitalism is "one dimensional" since he bears no trace of the conflicts which make him multi-dimensional and capable of change. This is why Marcuse believe that people under Liberal Western capitalism are no freer than people under totalitarian role, their oppression is just transparent. Capitalism is "enslaving us softly", not by mean of violent oppression but rather through comfortable temptation.
For Marcuse the one dimensional man is closely related to both consumerism and mass media that together serve as an ideological apparatus which reproduces itself through its subjects. This apparatus promotes conformity and is aimed at preventing resistance.
See also: cultural industry