Hard one - what is a dollar? If you have a balance that you see in some app, how can you tell that what you have there is a dollar?
And I don't mean in a trivial way ($ sign next to the number).
Discussion
You can't. Not unless you can audit the app provider company.
If you can buy bitcoin for it at your address, it was a dollar. Probably :-)
That's easy. Can it buy me a dollar's worth of stuff? "Stuff" including a physical $1 bill. If yes then it's a dollar.
I like the question.
I think the answer depends on how do you define, or, what do you mean by "there is a dollar".
What you see as your account balance in an app is the bank liability to you. In this sense, this liability is real.
Of course, they don't have physical dollar bills in a vault. They have some fraction of their liabilities as a reserve...
Yes. I think this is probably the only really correct answer. Dollar is in the head.
I would add that not only now, but also in the future. When there was a parity between euro and dollar, one euro could buy you one dollar, but it was not a dollar.
And physical bills might not be available, it's not a question of value, but liquidity. In Panama or Argentina, papers with dead us presidents are in short supply and people have to use another forms of usd.
Well I added the "including a dollar bill" because Applebee's gift cards can't buy you dollar bills. A dollar in bank account that can withdraw a dollar from an ATM is a dollar.
The temporal axiom you add probably completes the definition, I hadn't considered that when answering your question.