Finally one student raised his hand, and started to phrase his answer as I looked at him expectantly. I could tell he had precisely the right idea in mind, the one that would make everything come through beautifully. He had a ghost of a smile as he talked, and I smiled back: I knew the suggestion he had in his mind, it was the same as the one in my mind, and he knew that I knew, and I knew that he knew that I knew. But none of the other sixty or eighty people present had any clue. Yet there had been no communication between us that all the others had not been party of. Sweet moment of intellectual closeness! Normally, that sometimes happens in one-on-one research, but not in class.
Then the student said one more word, and everything came crashing down: he actually had the wrong idea. Oh, no! I had imagined extra sensory communication of brain waves, but it was all a fantasy!