When we talk about rationality, we're generally talking about either epistemic rationality (systematic methods of finding out the truth) or instrumental rationality (systematic methods of making the world more like we would like it to be). We can discuss these in the forms of probability theory and decision theory, but this doesn't fully cover the difficulty of being rational as a human. There is a lot more to rationality than just the formal theories.
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This post is part of the Rerunning the Sequences series, where we'll be going through Eliezer Yudkowsky's old posts in order so that people who are interested can (re-)read and discuss them. The previous post was 3 Levels of Rationality Verification, and you can use the sequence_reruns tag or rss feed to follow the rest of the series.
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