The currency that defines an economic period in a society is most definitely a medium. Perhaps not a medium for expressing ideas or concepts, but a medium for expressing value and worth.
Early economies are sometimes incorrectly thought of as limited to primitive, person-to-person, bartering of goods. However, the Chinese seem to have had systems of currency as early as 1122 B.C. The cowry shell satisfied the dual criteria of portability and limited availability necessary for it to become a tool of trade.
Later, cowry imitations were crafted in stone, and in different metals, so that the fragile shells themselves did not have to be used. Other, later forms of Chinese currency included inscribed replicas of a farmer's spade and a type of curved knife. Both "spades" and "knives" had a denomination and a place of minting inscribed on them. Finally, the more contemporary Chinese coinage appeared, with its circular form and a square piece removed from the center.
These knife and spade currencies became defunct for some pressing reason. Perhaps trends changed in what the populace perceived as a valuable shape or material. Maybe the common citizen somehow became comfortable with the idea of a unit of value no longer resembling the objects it could buy.
What then is going to happen to our own society, with money replaced by digital representations? The cowry shell was imitated in stone to improve its longevity and transportability. Likewise, we replace the paper dollar with digital information to improve durability and the speed of transaction. Does this mean that our economies are getting more efficient? If so, what are we getting more efficient at?
Matt Hall (firstname.lastname@example.org)