Once upon a time there lived a pencil eraser who was very good at his job, or so it thought until it came upon a marking it could not remove. "I cannot remove this marking," the eraser apologized to the paper, after trying again and again to remove it. The paper said, "You must keep trying, for this mark does not belong," and so the eraser rubbed and rubbed and rubbed and brushed its eraser lint away, but still the mark remained.

By and by, another eraser came along, and the pencil eraser looked at the new eraser and saw how pale it was, and it said, "I have never seen a pencil eraser like you before," and the other eraser said, "That is because I am not a pencil eraser," and the pencil eraser said, "What are you?" and the other eraser said, "I am an ink eraser, and I specialize in removing ink markings from paper," and the pencil eraser said, "What is ink?" and the ink eraser said, "Ink is a marking that pencil erasers cannot remove," and so the pencil eraser stepped aside to let the ink eraser work.

The ink eraser rubbed and rubbed and rubbed, and by and by the ink marking faded and disappeared, and the ink eraser went on its way, and the pencil eraser said, "How did the ink eraser erase the ink marking when I could not?" and the pencil eraser became unhappy but all the more determined and by and by, when it happened upon another ink marking, it said, "This time I will erase the ink marking myself," and it rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed and rubbed until the pencil eraser himself was all gone.

Had the pencil eraser still lived, it would have said, "Now that I am all gone, I cannot even erase ordinary pencil markings. I have learned that I have an important purpose in life, and now I know that it is better to do what I know how to do than to destroy myself attempting to do what I was never meant to do." And with that, the pencil eraser would have lived happily ever after, except, of course, that it was all gone.