modern fiat currencies have no intrinsic value and their real value is derived from all the underlying value systems in an economy.

http://en.wikipedia.org/wiki/Money_illusion

This is false, as modern fiat currencies have no intrinsic value and their real value is derived from all the underlying value systems in an economy, e.g., sound government, sound economics, sound education, sound legal system, sound defence, etc. The change in this real value over time is indicated by the change in the Consumer Price Index over time.