Intellectually stimulating videos

Joseph Stiglitz and Paul Krugman had a discussion about economics back in October 2012 that ran for an hour and a half. What other intellectually stimulating videos exist out there? I just want to sit back and learn stuff, and so either a friendly discussion or a partisan debate (where the debaters are equally matched) could work.
posted by SollosQ on Jan 17, 2013 - 13 answers