A little boy was spending his Saturday morning playing in his sandbox. He had with him his box of cars and trucks, his plastic pail, and a shiny, red plastic shovel. In the process of creating roads and tunnels in the soft sand, he discovered a large rock in the middle of the sandbox.
The boy dug around the rock, managing to dislodge it from the dirt. With no little bit of struggle, he pushed and nudged the rock across the sandbox by using his feet. (He was a very small boy and the rock was very huge.)
When the boy got the rock to the edge of the sandbox, however, he found that he couldn't roll it up and over the little wall. Determined, the little boy shoved, pushed, and pried, but every time he thought he had made some progress...