Imagine that Archimedes of Syracuse invented a device that allows you to talk to him. Imagine the possibilities for improving history! Unfortunately, the device will not literally transmit your words - it transmits cognitive strategies. If you advise giving women the vote, it comes out as advising finding a wise tyrant, the Greek ideal of political discourse. Under such restrictions, what do you say to Archimedes? In other words, how can you communicate general thinking patterns which will lead to right answers, as opposed to cached content?
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 Useless Medical Disclaimers, 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.