William Feller was a probability theorist at Princeton University. One day he and his wife wanted to move a large table from one room of their large house to another, but, try as they might, they couldn’t get it though the door. They pushed and pulled and tipped the table on its side and generally tried everything they could, but it just wouldn’t go. Eventually, Feller went back to his desk and worked out a mathematical proof that the table would never be able to pass through the door. While he was doing this, his wife got the table through the door.
