 Some controversies persist on the substance of money. It was part of historical debates over the gold standard and “bimetallism”, and more recently there has been philosophical discussion of electronic money (Smith &amp; Searle 2003) and “cryptocurrencies” such as bitcoin. An ongoing problem for work in the nature of money is the blurring of distinctions between questions about ontology, about the evolution of money, about what drives the money supply, and about what makes a monetary system stable.