Taking a solemn oath to promise never to write a program that analyses other programs? - That's how Professor Brailsford felt when he first understood undecidability. Latest in our series on the History of Undecidability Undecidability Tangent (History of Undecidability Part 1): http://youtu.be/nsZsd5qtbo4 Barber & Russell Paradoxes (History of Undecidability Part 2): http://youtu.be/FK3kifY-geM Turing & the Halting Problem: http://youtu.be/macM_MtS_w4 Busy Beaver Turing Machines: http://youtu.be/CE8UhcyJS0I Shellshock, The Bashdoor Bug: http://youtu.be/MyldPMn95kk History of Undecidability (Playlist): http://www.youtube.com/playlist?list=PLzH6n4zXuckpIQPv8hiHpJkSyv0fmXEYr http://www.facebook.com/computerphile https://twitter.com/computer_phile This video was filmed and edited by Sean Riley. Computer Science at the University of Nottingham: http://bit.ly/nottscomputer Computerphile is a sister project to Brady Haran's Numberphile. See the full list of Brady's video projects at: http://bit.ly/bradychannels