Paper money is a relatively recent invention.  It was first used in China around the 13th century, and was later adopted in Europe and elsewhere.  For a long time, paper money was viewed with suspicion.  The reason was that it wasn’t “real”.  Sure, the paper said you had so many pounds or francs or marks or dollars or whatever, but who was backing up that paper?  It was usually a private bank, so if that bank went bankrupt, your paper money was worthless.  Gold and silver were trustworthy—you could always take coins with you.  This is the way much of the world worked for a long time.  In fact, it wasn’t unusual to circulate gold and silver coins from ancient Rome and Mesopotamia as recently as the 19th century.  Ultimately, it was about the value of the metal. Metal isn’t the only thing that can have value ascribed to it.  After all, gold and silver are only valuable because enough people agree that they are; these metals aren’...