"Why are we down in this hole digging a ditch when our boss is standing up there in the shade of a tree?" asked the first ditch digger.
"I don't know," responded the other. "I'll ask him."
So he climbed out of the hole, went up to their boss and asked, "Why are we digging in the hot sun and you're standing in the shade?"
"Intelligence," the boss said.
"What do you mean, intelligence?"
"Well, I'll show you," the boss replied. "I'll put my hand on this tree and I want you to hit it with your shovel as hard as you can."
The ditch digger took a mighty swing but the boss removed his hand and the ditch digger hit the tree. The boss said, "That's intelligence!"
So the ditch digger went back to his hole. His friend asked, "What did he say?"
"He said we're down here because of intelligence."
"What's intelligence?" asked the friend.
The ditch digger put his hand on his face and said, "Take your shovel and hit my hand."