Up the XVIIth century, various monetary system created by banking institution coexist in the same country. But, in order to increase their power and to simplify the transaction, political leaders impose a single money.
For example in France, Louis XIV imposes a single currency system at the end of XVIIth century. The main reason of this action was to facilitate tax collection. Tax collection was previously made directly by the collection of good which are produced (wheat, animals,...) or duties. Louis XIV needs to collect a huge amount of taxes to finance the French army and its multiple wars.
The idea of single state currency dominates as it simplify trading and made company accounting easier.
The multi-monetarism consider the difference of the various monetary systems which are created in the XXth century: communism monetary system, liberal monetary system, inflationist monetary system. It came to the conclusion that either a money guarantee the availability of goods but in this case leads to unemployment, or can offer a full employment but in this case, some goods will not be available at any time.
At the age of computerization, the main argument for a single monetary system: simplicity is not valid anymore. As computer makes accounting easy, an economic system based on multiple currency can be considered.
Author: Hector Archytas