A man calls Animal Control to get a crazed gorilla off his roof. A van pulls up and an old man gets out, carrying a small dog, a baseball bat and a gun. He hands the man the gun.

"OK, here's what we do. I'm going to go up onto your roof and threaten the gorilla with this baseball bat until he falls down. When he falls down, this little dog will bite him in the balls until he's incapacitated."

"Great," says the man, "but what's the gun for?"

"If I fall down instead of the gorilla, shoot the dog."