When I was an undergraduate at U.C. Berkeley, there were a bunch of lunatics wandering around Sproul Plaza and Telegraph Ave. They sometimes had invisible friends with whom they'd have very animated conversations. This one unfortunate woman was very intelligent, highly educated and stark raving mad. She'd have these fascinating conversations with her invisible friend about Cartesian Dualism and various aspects of phenomenological existentialism. On occasion, I'd follow her at a respectful distance and try to gain a few pearls of wisdom. Unfortunately the local brats would sometimes see her and taunt her with insults. To this day if I hear someone having an animated conversation by himself, I first assume out of old habit that the person is insane. Then I remember it is more likely the person is talking on a cellular telephone (much less interesting).

Gary