Robin Williams, one of the greatest comics of his generation who spoke openly about his battles with depression, took his own life at his home in California Monday. He was 63, and the nation and world today mourns the loss of a comic genius known for many roles in television, film, and on stage as a manic stand-up with incredible improvisational skills. Our guests: Midday film critic Christopher Llewellyn Reed, chair of the Film and Video Dept. at Stevenson University; Baltimore Sun television critic David Zurawik; and Scott Weems, author of "Ha! The Science of When we Laugh and Why."