When he was at the Lawrence Livermore Laboratory—a place that used to do nukes, but has now decided that orthodox global warming pays better—William Newcomb devised the following puzzle, which some say is a paradox. You will play a game against an evil entity that can perfectly predict your future actions. Just for the sake of giving the evil one a name, let’s call him “Bill”. Bill is evil because he likes to taunt you with the possibility of making money, only to jerk that chance away from you at the last moment. Here’s what Bill does, as traditionally described....