What I mean is that money is not backed up by law of any sort. Gold, silver, fiat, nails.
You and I and everyone else decides what to trade with based upon our circumstances. A money will arise out of this and it need not be decreed by law. That is what I am saying. It starts with barter. If two cities are using media of exchange that are valued as worthless to each other, they will begin with barter if they want each others’ goods and then a new medium will arise between those two cities ad infintum.