"Professor, what is Science?"
"Science is looking for a black cat in a dark room."
"And please, Professor, what is Philosophy?"
"Philosophy is looking for a black cat in a dark room, except that there is no cat in the room."
"Hmmm . . . and what, please, is Psychoanalysis"?
"Psychoanalysis is looking for a black cat in a dark room -- in which there is no cat -- but finding one anyway."
(Heard on the radio.)