Marco Polo describes a bridge, stone by stone.
"But which is the stone that holds up the bridge?" asks Kubla Khan.
"The bridge is not held by this or that stone" replies Marco,
"but by the line of the arch that thet form."
Kubla Khan remains silent, thinking.
Then he adds, "why are you talking to me about stones?
It's only the arch which concerns me"
"Without the stones, there is no bridge."