Let Mock try to explain.
Assume there is no gold in Ft. Knox.(there probably isn't)
Then it becomes a function of the economy, debyt and most importantly, THE MONEY SUPPLY.
Gold is a finite commodity. So are others.
A fiat currency is just that. Fiat, you can print it till the ink runs red.
There is a finite amount if goods and if you havce an infinite amount of fiat money, it doesn't matter.You can't buy squat.