A professor stood before his philosophy class and had some items in
front of him. When the class began, he wordlessly picked up a very large,
empty mayonnaise jar and proceeded to fill it with golf balls. He then a
asked the students if the jar was full. They agreed that it was.
The professor then picked up a box of pebbles and poured them into the
jar. He shook the jar lightly. The pebbles rolled into the open areas between
the golf balls. He then asked the students again if the jar was full. They agreed it was.
The professor next picked up a box of sand and poured it into the jar. Of course,
the sand filled up everything else. He asked once more if the jar was full. The students responded with a unanimous ‘yes.’