Honestly, I know it's an impossible task, as I have already mentioned, bitcoins don't really exist.
They exist just as much as inches or meters or megabytes exist - they're all units of measurement. And the Bitcoin software certainly exists - so the Bitcoins themselves are measurement units within that software.
Inches and meters are units of distance. Megabytes are units of information. These are both properties of the physical universe, defined in terms of experimental measurements.
What are bitcoins units of? Can you offer a non-circular definition?
Bitcoin is *effectively* a currency because that is what it does and how people use it. Although, it does have some special properties that make it a very novel and unusual type of currency.
Just because some people use it for barter doesn't mean it's a currency. Would you say sheep are currency just because people in Afghanistan use them for trade? At most it's a local currency because it lacks the typical "generally accepted" part of it's definition.
A currency is any economic good routinely used within a community for indirect exchange. Local currencies are still currencies, and in a sense
all currencies are local--none of them are accepted universally.
A commodity always has a use by itself. If gold were not used as medium of exchange or storage of value it would still be useful because you can make useful things with it, such as electronics and jewelry.
Bitcoin does not have that property.
What about the use of Bitcoin as a novelty? When Bitcoin got started it had no other use but as novelty much like gold jewelry.
The bitcoin system may have novelty value, but bitcoins were never novelties because, as has already been stated, they don't exist in any sense other than as completely abstract units of measurement, like points in a game.
If the bitcoin system can be considered a system of currency, the economic good it is based on is not a commodity, but a service: the distributed service offered by every other bitcoin user of recognizing your participation as an equal, and enforcing the rules of the game.
Hmmmm - if you were the only one in the world to have gold, would it not be similarly worthless?
No, because gold has unique and valuable physical properties, even if you completely disregard its use as a currency. There would be value in direct use even without anyone to trade with, and likely even more value in terms of direct exchange.