Questioning fundamental assumptions in economics or any belief system is useful. In anthropology cultures and economies are sometimes to referred to by thier primary output or function. For example, the rise of the corn economy among meso-americans or the trade economies of the early mediterranean traders. It is popular to refer to our age as the information economy. As a thought experiment with a colleague I crafted a currency idea for an energy economy.
Currencies are often based upon primary economic functions. It is unknown if the ancient Cuneiform Sumerien tablets showing the first examples of writing often represented grain holdings and may have been a form of money or reciept.
Current economies base their money on government debt and whatever else a central bank purchases and holds. Below is a thought experiment for an energy based currency. Currencies like cultures are transitory but the illusion of permanence is a necessity for the orderly function of a given society. An energy based currency is unlikely to ever exist but poses an interesting counterpoint to a currency based on debt.
Electricity vs. gold and debt for currency