I was discussing LessWrong and rationality with a few people the other day, and I hit upon a common snag in the conversation.
My conversation partners agreed that rationality is a good idea in general, agreed that there are things you personally can do to improve your decision-making. But their point of view was that, while this is a nice ideal to strive to for yourself, there's little progress that could be made in the general population, who will remain irrational. Since one of the missions of CFAR/LW is to raise the sanity waterline, this is of course a problem.
So here's my question, something I was unable to think of in the spur of the argument - what are good examples of rationality techniques that have already become commonly used in the general population? E.g., one could say "the scientific method", which is certainly a kind of rationality technique that's going semi-wide adoption (though nowhere near universal). Are there any other examples? If you send a random from today back in time, other than specific advances in science, will there be anything they could teach people from the old days in terms of general thinking?