The old man pointed to a large cubic block, perhaps a metre on each side.
“Push the block to the top of the hill,” he told the boy.
The boy pushed and heaved with all his might.
But the block didn’t move.
“You are pushing too hard…” the man said.
“Too hard?” said the boy. “Surely I’m not pushing hard enough?”
“Put your finger on the block…” the man said.
The boy did so, and the block began to move, as if by itself.
He took his finger off, and the block stopped moving.
He put his finger back on, and it started moving again.