An eccentric philosophy professor gave a one question final exam
 after a semester dealing with a  broad array of topics.
 
 The class was already seated and ready to go when the professor
 picked up his chair, plopped it on his desk and wrote on the
 board: "Using everything we have learned this semester, prove that
 this chair does  not exist."
 
 Fingers flew, erasers erased, notebooks were filled in furious
 fashion. Some students wrote over 30 pages in one hour attempting
 to refute the existence of the chair. One member of the class
 however, was up and finished in less than a minute.
 
 Weeks later when the grades were posted, the rest of the group
 wondered how he could have gotten an A when he had barely written
 anything at all. His answer consisted of two words: "What chair?"