Fiat currencies (that is, currency that has no intrinsic value) has existed for at least 1300 years, if not longer. They are not based on air, they are based on trust in an institution and its ability to maintain its value through whatever means it has available.
Rare metals are natural exchanges of value even then gold has no utilitarian value for most people because they are scarce and the quality in circulation does not usually change dramatically. Thus, it can become a medium of exchange. Government backed currencies have similarities, but instead of mining the earth, a government (or corporation in the case of company stores) can "mine" its coercive power to produce more currency.
The point is, fiat currencies are ephemeral, but so are intrinsically backed currencies. The inherent power of exchange for something like gold is not especially more powerful or reliable than the inherent power or reliability of the US Govt with regards to a medium of exchange.
Rare metals are natural exchanges of value even then gold has no utilitarian value for most people because they are scarce and the quality in circulation does not usually change dramatically. Thus, it can become a medium of exchange. Government backed currencies have similarities, but instead of mining the earth, a government (or corporation in the case of company stores) can "mine" its coercive power to produce more currency.
The point is, fiat currencies are ephemeral, but so are intrinsically backed currencies. The inherent power of exchange for something like gold is not especially more powerful or reliable than the inherent power or reliability of the US Govt with regards to a medium of exchange.