"The solution societies find, as they get more specialized, is to make the trade into a two-step process. Instead of trading violins directly for potatoes, you trade violins for, say, silver, which you can then trade again for anything else you need. The intermediate stuff-- the medium of exchange-- can be anything that's rare and portable. Historically metals have been the most common, but recently we've been using a medium of exchange, called the dollar, that doesn't physically exist. It works as a medium of exchange, however, because its rarity is guaranteed by the U.S. Government."
The "two-step process" part reminds me of pointers, strangely. The metaphor doesn't make much sense though. A dollar points to wealth? Dereferencing a dollar obtains the wealth it points to?