 The commodity theory of money was defended by many classical economists and can still be found in most economics textbooks (Mankiw 2009, Parkin 2011). This latter fact is curious since it has provoked serious and sustained critique. An obvious flaw is that it has difficulties in explaining inflation, the decreasing value of money over time (Innes 1913, Keynes 1936). It has also been challenged on the grounds that it is historically inaccurate. For example, recent anthropological studies question the idea that early societies went from a barter economy to money; instead money seems to have arisen to keep track of pre-existing credit relationships (Graeber 2011, Martin 2013, Douglas 2016, Part III).