This is a very special episode of Expert to Expert. We were very fortunate to get some time with renowned computer scientist and Microsoft Technical Fellow Butler Lampson. Butler’s impact on general purpose computing is profound. Personal computing as it exists today is in part the result of the great work done by Butler over the past 30 years.   Programming language designer and high priest of the lamda calculus Erik Meijer hosts this episode of E2E and Erik and Butler cover a very wide swath of computing topics. It's simply beautiful and very deep geekiness. In fact, this is one of my favorite Channel 9 conversations of late. I know you will enjoy both the usual real conversational aspect of this and the depth of historical insight into some of the core aspects and unresolved problems of general purpose personal computing. Go get some popcorn, stream this into your XBox or Media Center and learn from one of our industry's pioneers who still has a great deal to offer to the world of personal computing. What's Butler working on these days, you wonder? What's top of mind for him as it relates to today's biggest challenges in computing? What does software security really mean? How many levels of software abstraction do we need? Why is data synchronization such a hard problem? What is software embodiment, exactly (Butler will be presenting his thinking on software embodiment at PDC09, as part of the new Technical Leaders track (something yours truly is responsible for - I hope you plan on attending these very special sessions and if not you will be able to watch them right here on Channel 9))? Tune in and meet a true legend in our industry. Microsoft is very forunate to have Butler Lampson thinking about some of the hardest problems we face as an industry and ensuring that Microsoft is capable of tackling these challenges in a way that extends the solutions for long term relevance in a changing and unpredictable environment.