A homeless and a scientist sit together on a train. The scientist gets bored and decides to play a game based on questions and answers, whoever gets a wrong answer has to pay. Since the homeless guy only has one dollar they decide that if the homeless guy gets a question wrong he has to pay one dollar but if the scientist gets it wrong he pays what he has, $352.
The scientist goes first, he points out the window, "Can you see that star?" he tells the homeless. "Tell me the distance of the nearest star in that constallation." Off course the homeless guy had no idea so he ended up paying his dollar. Now the homeless' turn, "Do you see that mountain?", he tells the scientist. "What animal goes up the mountain on four feet and comes down the mountain on six feet?". The scientist thinks and thinks but nothing comes up. Arriving at the final stop, the scientist finally gives up and pays $352, but before exiting he says "How can this be possible, with all these years of study. Please you have to tell me what animal goes up the mountain on four feet and comes down on six!" So the homeless reaches for his pocket and gives him one dollar.
Moral: common sense is better than knowledge(umm... generally speaking)