A biologist, a statistician, a mathematician and a computer scientist are on
a photo-safari in Africa.  As they're driving along the savannah in their
jeep, they stop and scout the horizon with their binoculars.

The biologist: "Look!  A herd of zebras!  And there's a white zebra!
	Fantastic!  We'll be famous!"
The statistician: "Hey, calm down, it's not significant.  We only know
	there's one white zebra."
The mathematician: "Actually, we only know there exists a zebra, which is
	white on one side."
The computer scientist : "Oh, no!  A special case!"