Brains are slow. They need to cache as much as they can. They store answers to questions, so that no new thought is required to answer. Answers copied from others can end up in your head without you ever examining them closely. This makes you say things that you'd never believe if you thought them through. So examine your cached thoughts! Are they true?
Discuss the post here (rather than in the comments to the original post).
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 Do We Believe Everything We're Told?, and you can use the sequence_reruns tag or rss feed to follow the rest of the series.
Sequence reruns are a community-driven effort. You can participate by re-reading the sequence post, discussing it here, posting the next day's sequence reruns post, or summarizing forthcoming articles on the wiki. Go here for more details, or to have meta discussions about the Rerunning the Sequences series.