A scorpion, not knowing how to swim, asked a frog to carry it across the river. “Do I look like a fool?” said the frog. “You’d sting me if I let you on my back!”

“Be logical,” said the scorpion. “If I stung you I’d certainly drown myself.”

“That’s true,” the frog acknowledged. “Climb aboard, then!” But no sooner than they were halfway across the river, the scorpion stung the frog, and they both began to thrash and drown. “Why on earth did you do that?” the frog said morosely. “Now we’re both going to die.”

“I can’t help it,” said the scorpion. “It’s my nature.”