A phrase I picked up a few days ago, I think from a discussion of a study of how people assessed other people in their decision-making is:
"By definition, most people are in the majority." It blew my mind, because it sounds like Garrison Keillor's Lake Woebegon, where all children are above average. But it's really the same logic, reversed. Using a mathematical truth, it states a conclusion that's not obvious.
The discussion (perhaps in the Sunday Post Outlook) was on research into people's behavior in the Prisoner's Dilemma situations (where it's to your self-interest to rat on the other guy, but the best course of action for both is to zip lips). Apparently people are surprisingly apt to adopt the best course, surprisingly at least to economists who have no imagination. An evolutionist would say that, if it's the best course, people would have evolved to figure it out.
The logic of the argument is that people make a decision by looking at themselves, then figuring that other players in the game will be and act like themselves. The scientist said this was rational, because most people will be in the majority most of the time.
Still blows my mind.