I can't credit a source for this story because I can't find any. I do recall being told it as an illustration of the human desire for meaning. It goes like this:
Once there was a prisoner who was forced to do hard labor. He was assigned to act like a mule, walking around pushing the beam that would turn the heavy stone of a mill located just outside the prison. This work caused aches in his arms and his back and roughed up his hands. But he kept himself motivated by thinking about the output of his work. He took some pride in thinking about how much grain he ground into flour that would be made into bread for the community.
Every day, he could feel the work he did made a difference in people's lives and that his efforts bore fruit. Finally, his sentence was up, and he finally got to walk outside the prison walls. He hurried over to see the mill stone that he had put in motion for so many years to get the thrill of seeing what his work had accomplished.
The prison guard laughed at him because no grain ever was ground by that stone. Realizing that all that effort was futile, the ex-prisoner could not even step into his freedom and collapsed in anguish.
That's the classic version, as I recall it, and it has clear echoes of Sisyphus, though here Sisyphus is allowed to harbor the illusion that each boulder he rolls up is a new one, and only learns that all his effort was futile after his sentence is up.
I'd suggest that where some people are is slightly different. There are several prisoners together in the same situation. However, some of them have cells with a window that lets them catch a glimpse of the millstone. What they realize after some time passes is that no one every delivers grain there, and no one ever picks up flour.
They can't be 100% sure, of course, because they only have a limited view through the window. However, they can infer from what they can see .They start telling their fellow prisoners that they don't believe their works does anything.
Then their fellow prisoners whose cells do not have a view of the mill insist that they are telling them lies and that must believe the guards who know better than they. These prisoner would come to resent the ones who try to tell them that things are not what they seem because they must believe that their suffering has purpose. Freedom and truth are anathema to them because it would force them to confront the lack of meaning in all the work they have done.
Related: http://uncommoncontent.blogspot.com/2013/11/its-meaningful-life.html
