[lottin]

If you fork the bitcoin blockchain you have now two ledgers, each one telling you that a certain number of bitcoins really exist. Who is to say that one is right and the other is wrong? In this scenario, it's debatable how many bitcoins are in existence.

[sowbug]

You might want to read the Bitcoin whitepaper. There is zero ambiguity in the situation you describe. That is the essence of the proof-of-work (or proof-of-stake, take your pick) solution to the Byzantine generals problem.

[lottin]

The ambiguity has to do with the fact that we don't know for sure which blockchain will prevail, because the protocol is unenforceable.