frog & scorpion

One day, a scorpion stood on the side of a stream and asked a frog to carry it to the other side.

Frog: How do I know you won't sting me?

Scorpion: Because if I sting you, I'll drown.

The frog thought about it and realized that the scorpion was right. So he put the scorpion on his back and started ferrying him. But midway across the stream, the scorpion plunged its stinger into the frog's back. As they both began to drown. 

 

Frog: Why?

Scorpion: Because it is my nature.

p/s: Every word had a hidden meaning, and every hidden meaning had weight, and every weight had its own special place on the scale of self-interest.