I'll leave that for Mr. Popper. Unfortunately, the supporters of religion tend to mangle his arguments. In regards to falsification, they will argue that scientific theories can't be believed since there is always the chance that they might be proven wrong. On the other hand, they will claim that religious beliefs are bulletproof since they can never be disproven. Of course, those of us whose neurons are still firing properly understand that this is pretty much bass-ackwards, but such an argument can have some appeal for the lay audience.
Truth is unknowable.
Perhaps I should elaborate a bit. Nevertheless, I believe from your careful wording you are aware of this. That's applying a rather harsh standard. That's the best we can do. In the end it has a good dose of subjectivism.