Inflation is theft. You'll hear that a lot and some think it's just a hyperbolic statement but it's a very true statement about our current money system.
Now let me clear inflation can occur because of supply and demand. That's obviously not theft, but inflation does happen because of governments increasing the money supply.
Say you have an obligation to pay everyone over 65 a pension but you've mismanaged the money. You can either increase taxes (unpopular), default on your obligations (unrest) or create more money to cover your obligations.
Most countries do the latter which results in the value and purchasing power of the currency you hold to go down in value, hence a type of regressive tax that affects those lower on the socio-economic ladder the most as they tend to not hold assets.
We as Americans also export our debt on everyone else as other countries hold treasury assets which reduce their value. At some point, countries are going to stop trading their hard-won resources like natural gas, oil and mineral deposits for paper that can printed arbitrarily.
Hard money is the ultimate property.
Gold was hard money for a thousand years. Hard money, sometimes called a bearer asset, is the ultimate money. You can exchange money for all other types of property, goods and services. You earn money based on labor and you can't counterfeit labor. The work is done or it isn't.
So when you work to earn money, that is an exchange of the energy, the labor that went into creating the value of that money. With money printing at the whim of a central bank, it's theft because you steal the value of the labor that went into earning the money.