Today's post, The Fear of Common Knowledge was originally published on 09 July 2008. A summary (taken from the LW wiki):

A discussion of an interesting kind of lie, in which someone tells a lie that the person they're speaking to knows is a lie, but doesn't know that the person who told the lie knows that they know it's a lie.

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 Where Recursive Justification Hits Bottom, 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.