I see that the same word : cash, is often used to talk about 2 radicals different things.
In the first definition, cash distinguishes two different type of money : "ledgered" money, versus "owned by the bearer" ones.Wire transfer, checks, swipe card, versus bills.
In Mises terminology, we might be tempted to think that this is what he refers as "credit money" versus "fiat money".
For Mises, Credit money is any claim on someone or something falling due in the future that is used as a general medium of exchange.
A bank balance represents a claim issued by the bank, that you can redeem for fiat money, and this is what is used instead of fiat money for the majority of exchanges today.
But in the past, bank issued notes, which are both "owned by the bearer" and credit money, felt into the definition of "cash", and considered more or less equivalent to government's issued money. (Milton Friedman explaining that in A Monetary History of the United States)
With this definition, is Bitcoin cash ? because the peculiar thing is that it is ledgered money but still "owned by the bearer".
I would empirically say that the specific feature of cash widely used today is whether or not the money is ledgered.
This would explain why any "Toward cashless society" articles that you can read in the web do not think that moving Bitcoin with your mobile phone is similar to using cash.
We should note that Bitcoin is the first ledgered money that is still "owned by the bearer".
But it is also the first ledgered money that does not represent Credit Money. (to my knowledge)
The second definition that I see arising from the web, and I think is better suited is the presence of third party.Under this new definition, any medium of exchange that can be transfered between two peers without any approval by a third party is considered cash.
This definition is simple and clear cut. Under this definition, Bitcoin is cash, no other discussion needed.
Contrary to the previous definition, a "Toward cashless society" article would not focus on the fact that money becomes more and more ledgered.
It would focus on the increasing requirement of approval of a third party for any exchange between two persons.
Interestingly enough, this is the definition implied by Milton Friedman in 1999 when he was speaking of e-cash.
https://www.youtube.com/watch?v=fYD17h6hlCs[UPDATE]
This second definition is also the definition that Satoshi is using.
[/UPDATE]
So the question is which definition are you using ?