Feynmann:
There really is no duality of money. If you convert degrees in farenheit to degrees in celsius through an equation, does that equation have any concrete value or measurement by itself? Is it tangible or useful in any other way than as it relates to temperature in degrees?
No.
Perhaps somebody working with that equation on a daily basis might begin to think that it actually has some kind of independent existence or meaning, but it doesn’t.
The fact that US dollars provide a valuable source of liquidity and a medium of exchange actually creates a certain tangible value for them. Looked at this way, money is a service, that provides value. But, I don’t think this what you mean when you refer to its “duality” (which again, it doesn’t have.)
Now, pretend that the Farenheit and Celsius scales are in constant flux, so that there is no fixed equation to convert between them. What we need is a floating conversion equation, one that changes to reflect the variability in the scales.
If we create such an equation let’s call it the “FC unit” or “FC,” an observer can do interesting things with these numbers. And, people will. Scientists that work with Farenheit will naturally relate all the changes in the equation in terms of Farenheit so that from their perspective Farenheit doesn’t change. From their perspective both Celsius and the FC will appear to fluctuate, while the value of farenheit remains as steady as a rock. Perhaps these scientists will begin to wonder at the ignorant fools who attempt to work with the FC or Celsius. Why bother, when Farenheit is an absolute?
Of course scientists working with Celsius will do the same thing from their perspective and wonder about the fools working with Farenheit.
After a time, if their is a medium of exchange between these two groups in terms of scientific knowledge, they may begin to relate the data in terms of the FC itself. Then the perspective shifts again, and it appears that Celsius and Farenheit move and the FC remains stable. The reality is that it’s all an illusion.
To look at at in another way, if you drive your car, you may say that the car is travelling at 50 mph. An observer inside the car may think that the car remains still, and that it’s the earth that’s moving. And, if the person is travelling in the direction of the rotation of the earth at exactly it’s speed of rotation, which is actually true is only a matter of perspective. MPH is only effective in terms of relating speed of a vehicle to the earth. The reality is that the earth is spinning, moving about the sun, which in turn is also in motion, within a galaxy in motion. There is no meaningful absolute speed at which we are travelling. There are just relationships between objects.