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 Kahn remains silent, reflecting. Then he adds: “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 by Italo Calvino, tr. by William Weaver, London: Vintage Books, [1972]1997 p. 74

This “parable of the bridge” in Italo Calvino’s novel Invisible Cities could be read as an illustration of the fundamental relation that ties together the element with the whole into something useful or meaningful. Without the elements, the whole is an abstraction and, without the whole as a structuring principle, the elements are simply separated, disorganized entities.

Maybe it could also apply to the ways by which empirical observations relate to a theory, or personal anecdotes to a broader historical perspective.

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Below are two etchings by Giovanni Battista Piranesi. The first one is retrieved from the volume 4 of his book Le antichità romane (1756): “Tav. XXIII. A. Elevazione del Ponte Ferrato” (on page 29). The four volumes can be viewed online over at The Theater that was Rome website (maintained by Brown University). The same illustration is also available in a large format over at Wikimedia Commons.

The second illustration is retrieved from The British Museum: “A View of Part of the Intended Bridge at Blackfriars, London, in August MDCCLXIIII” (1766). A more thourough description can be found at Bloomsbury Auctions:

Robert Mylne (1734-1811), Scottish architect, visited Rome between 1755 and 1758, where he developed a friendship with Piranesi, who had recently published his Antichita Romane. This revealed the amazing building techniques of the ancient Romans that so fascinated and influenced Mylne. Piranesi, in turn, requested drawings from Mylne to illustrate his Blackfriars Bridge under construction, producing this copper plate in Rome, but sending it to London to be printed. Hence it is an exceptional plate in falling outside Piranesi’s vast body of other work, inherited and re-issued by his sons, before passing through other hands in France and then back to Rome, to rest finally in the Calcografia.