On Cities, Building Blocks and Rocks

Marco Polo describes a bridge, stone by stone.

"But which is the stone that supports the bridge?" Kublai Khan asks.

"The bridge is not supported by one stone or another, " Marco answers, "but by the line of the arch that they form."

Kublai Khan remains silent, reflecting. Then he ads: "Why do you speak to me of the stones? It is only the arch that matters to me."

Polo answers: "without stones there is no arch." - Invisible Cities