Anything can be a currency so long as enough people agree there is value. Bristol (a smallish city in the UK) has it's own currency that can be used locally that is accepted by shop keepers etc. You can't pay your mortgage with it but you can buy you apples with it.
We could use shiny stones as currency if enough people agreed it had value.
I think you are thinking about currency within the confines of the current system (eg government, laws etc). What I am saying is that government and laws are only valid in our collective imaginations and therefore everything is imaginary and made up (the USD is just as imaginary as bitcoin, it's just that more people believe in the USD so it is mainstream) and we can collectively apply value to anything want to and remove value from anything we want to.
'if people agreed it had value' - That is a big if, don't trivialize it. The value of a currency is dependent on a ton of the properties I listed above.
We could use shiny stones as currency if enough people agreed it had value.
I think you are thinking about currency within the confines of the current system (eg government, laws etc). What I am saying is that government and laws are only valid in our collective imaginations and therefore everything is imaginary and made up (the USD is just as imaginary as bitcoin, it's just that more people believe in the USD so it is mainstream) and we can collectively apply value to anything want to and remove value from anything we want to.