At night, tired from a long work day, strange things surface. What would make me remember a story I hadn't thought about in decades—a story that isn't even mine, although it belongs to my childhood? When I was young, I loved to tell jokes. Knock-knock jokes in particular, as my son tells now, and when I was older, jokes from the "Truly Tasteless Jokes" series of books (I think there were many volumes; I had at least one of them, with a black cover). Then for some reason I stopped being able to remember jokes at all. I've rarely told any in my adult life, though I like to think I've managed to keep a sense of humor anyway. The jokes were often quite long, with complicated stories leading up to a punch line. This is probably why, in time, I became unable to tell them. I'd remember the punch line but not the setup. I do know that some of my old jokes were rather inappropriate, especially for a child telling them. One involved a rip-off artist in a house of il...