Originally Posted by
daredevil 
For practical purposes, as per the title of this thread, it seems like an exercise in futility to discern whether an ‘unbreakable’ promise is, in fact, ‘unbreakable.’
I suppose, in the context you state, since you believe it wholeheartedly, and intend to stick to it, it’s unbreakable. I also suppose that an AVRT exponent would assert that the aforementioned conversation is, at least in part, the lexicon of the AV.
In strict language and logic terms it’s totally clear to everyone that “I promise that 4 will never be a prime number” is an unbreakable promise, so the question is not “to discern whether an ‘unbreakable’ promise is, in fact, ‘unbreakable’. We know they exist. It is to try to prove that an ‘unbreakable’ promise may be, in fact, ‘breakable’.
In regards to a Big Plan, I cannot prove mine to anyone else, and anyone else cannot disprove mine to me or anyone else. Nevertheless, The Big Plan has incredible utility - as an “unbreakable promise”. And I speak from experience, as has been noted.