My question is similar a question already asked Decidability of the Riemann Hypothesis vs. the Goldbach Conjecture
But in general, given some well-known problems of mathematics for example the Riemann hypothesis and the Goldbach conjecture they have neither been proven nor disproven. But we know that the hypotheses are either true or false, right? So it is not a case of undecidable problems similar to the halting problem where Turing proved that the hypothesis is undecidable for a general algorithm and its input?
Or could it still be open that the Riemann hypothesis or similar unsolved problems could in fact turn out to be undecidable or if that is not the case, how can we prove or understand that the statement is not undecidable?
Given that a problem is undecidable and we want to prove that it is undecidable we create a new hypothesis H0: "The Problem number 42 is undecidable" and then we can prove with a counterexample that it is or isn't undecidable. But then could it not be the case the the H0 hypothesis itself is undecidable and we must investigate another meta-problem to first prove that the question of undecidable itself is not undecidable.
