There’s a joke. It’s actually one of the best jokes ever told in all the long history of human wit, not just because it’s funny—if you’ve got the chops to nail the delivery—but because it is an incredibly powerful measure of persons. You can tell a great deal about someone from how they respond to this joke. I might actually make it a point to tell it to the banker, the librarian, the alchemist and whatever the other one is. In fact, it’s so revealing that I’m going to tell it now and see whether my invisible interlocutor has anything to say about it.