He listens, puts together what Cambridge is saying with what little he knows of the man. He notices it's focused internally, and he isn't sure, entirely, what to make of it. He doubts the man hasn't lived through historic events and he doesn't really understand how a person is a person without being defined by the history they've lived through. He doesn't really understand this is a problem, either.

It leaves him puzzled, because he's not understanding.

"But changing things, environment, changes you. Change the past, you change the person you are now. So telling your past self anything about the time between you does change you, you still wouldn't be the same person."