In this short and simple Aesop’s fable (a fable is a very short story which is meant to illustrate a point or teach us a lesson. Usually, but not always, fables are stories about animals that talk like people. The lesson that a fable teaches us is called a moral), a scorpion, who couldn’t swim, asked a frog to carry him across the river on her back. The frog hesitated, saying, “I’m afraid you will attack me.” But the scorpion pointed out that it wouldn’t be in his interest to do that, because, if the frog died in the water, he would drown. So she consented.

As they were half way across the water, the scorpion suddenly whipped up his tail and stung the frog hard. As the poison spread through the frog and she began to sink, she whispered, “Why? Why did you do that, when now we must both die?”

“Because,” the scorpion replied sadly, “it’s in my nature to sting. I’m sorry.” As he spoke, they both disappeared beneath the water. The moral of the fable is that we can’t overcome our nature, even if it works against our interest.

However this story may seem negative; it is an example of what happens to us when we don’t pay attention to the "nature" of the individuals around us. Some are trustworthy and honorable while there are others who we say "you shouldn’t trust ‘em as far as you could throw ‘em."

One of the earliest known quotations is in a movie by Orson Welles, Confidential Report (1955 – based on his novel Mr. Arkadin). The concept is applied in all sorts of ways to analyses of history, or of recent events, on the “dark” side of human behavior.

There are, of course, elaborations. What if the scorpion wants to kill the frog as soon as they get to the other side of the river? Or will the frog drop the scorpion in the water to eat it when it’s drowned? Or could both be eaten by a fish or a bird? Etcetera. But the true meaning of the story is in it’s simplest form.