Another memory from Bob Dobbs:

After the end of the formal part of a Monday Night “performance” in 1978, I was eavesdropping on Marshall McLuhan engaging in some intellectual banter with a Professor. 
They were getting into the dialogue deeper and deeper when McLuhan all of a sudden said to his “colleague”:
“You’re trying to TELL me something.”
This was the end of their exchange and they each slowly turned to talk to somebody else.