The concept of a subliminal technological 'environment' shared by all of humankind is McLuhan's answer to the Freudian 'unconscious'.
The distinction between (unconscious) environment and (conscious) anti-environment, employed by McLuhan from 1964, is founded upon an earlier distinction between 'form' and 'content', and the maxim that 'the medium is the message'.
As McLuhan elaborates in Understanding Media (1964):
"the medium is the message" because it is the medium that shapes and controls the scale and form of human association and action. The content or uses of such media are as diverse as they are ineffectual in shaping the form of human association. Indeed, it is only too typical that the "content" of any medium blinds us to the character of the medium.1
By September 1964, McLuhan had reformulated his idea that 'the medium is the message' in terms of a media-environment.2
McLuhan, punning on his own phrase, sometimes describes the media-environment as a 'massage' writing in The Medium is the Massage (1967):
All media work us over completely. They are so pervasive in their personal, political, economic, aesthetic, psychological, moral, ethical, and social consequences that they leave no part of us untouched, unaffected, unaltered. The medium is the massage. Any understanding of social and cultural change is impossible without a knowledge of the way media work as environments.3
In fact it is clear from McLuhan's essay 'The Relation of Environment to Anti-Environment' (1966, revised version 1967) that what he is really concerned with in his analysis of media 'effects' are the dynamics between the 'unconscious' (environment) and 'consciousness'.
Here he says that 'Any new technology, any extension or amplification of human faculties given material embodiment, tends to create a new environment.'4
However, 'The ground rules, the pervasive structure, the overall pattern [of the environment] eludes perception except in so far as there is an anti-environment or a counter-situation constructed to provide a means of direct attention.'5
McLuhan's use of the terms 'anti-environment' and 'environment' distinguishes the concepts from the psychoanalytic 'conscious' and 'unconscious', and in fact, McLuhan's understanding of these terms is significantly different from Freud's.
Where Freud positions the 'unconscious' id in relation to 'consciousness', McLuhan takes the (unconscious) environment to be the primary state of awareness, and the (conscious) 'anti-environment' to be a privileged state of awareness.