Natural languages, by contrast, can refer to vague concepts which don’t have clear, fixed boundaries
I disagree. I think it’s merely the space is so large that it’s hard to pin down where the boundary is. However, language does define natural boundaries (that are slightly different for each person and language, and shift over time). E.g., see “Efficient compression in color naming and its evolution” by Zaslavsky et al.
The issue is you cannot prove this. If you’re considering any possible meaning, you will run into recursive meanings (e.g. “he wrote this”) which are non-terminating. So, the truthfulness of any sentence, including your claim here is not defined.
You might try limiting the number of steps in your interpretation: only meanings that terminate to a probability within N steps count; however, you still have to define or believe in the machine that runs your programs.
Now, I’m generally of the opinion that this is fine. Your brain is one such machine, and being able to assign probabilities is useful for letting your brain (and its associated genes) proliferate into the future. In fact, science is really just picking more refined machines to help us predict the future better. However, keep in mind that (1) this eventually boils down to “trust, don’t verify”, and (2) you’ve committed suicide in a number of worlds that don’t operate in the way you’ve limited yourself. I recently had an argument with a Buddhist whose point was essentially, “that’s the vast majority of worlds, so stop limiting yourself to logic and reason!”