person
also known as Reich

Author of The Greening of America, and in dialogue 73 the external trigger for a change in McLuhan's public formulation. Bob's account is that McLuhan held back "the user is the content" through the 1950s and 60s to secure the formal effect, and began saying it in the 1970s after Reich prompted him — which makes Reich the reason a suppressed half of the formula surfaced when it did.

Across the dialogues

73

Given a precise causal job — the outside prompt that made McLuhan release the half of his formula he had deliberately withheld for two decades

The withholding is presented as strategy rather than oversight, so an outside prompt is needed to explain the timing — the second half of the formula was available all along and released on cue.

"But then in the 70s, Charles Reich, I guess his name was, of The Greening of America, prompted him to start."
Bob Dobbshedgedqualifier: “I guess his name was”

Connections

Bob credits Reich with prompting McLuhan to start saying "the user is the content" in the 1970s.