 The centerpiece of Menger’s account is the non-intentional emergence of money (see Aydinonat 2008, Tieffenbach 2010). But his account also gives an implicit theory of the nature of money. Money is a simple causal-role kind, with any good that is highly liquid and marketable being money. Introductory economics textbooks tend to define money as a slightly more complicated role-kind: money is a store of value, a medium of exchange, and a unit of account (Arnold 2008, Mankiw 2016). Recent work in economics suggests a different set of functions for money. A striking feature of standard economic models is that money seems superfluous. In idealized neo-classical economies, there is no need for a medium of exchange, nor is it clear why price levels should affect the “real economy” of production and consumption. Thus economists have recently investigated the economic “frictions” that make money useful, and find that money contributes to efficiency in a market that has imperfect enforceability of contracts and limited record-keeping. In such an economy, money helps perform operations such as the search for trading partners. The overcoming of such economic “frictions” seems to be an alternative and perhaps underlying function of money. (See Diamond 1984, Kiyotaki &amp; Wright 1989, Kocherlakota 1998, Wright 2010, Smit, Buekens et al. 2016.)