2
$\begingroup$

Is there a notion in the literature of a theory which is locally consistent, in some sense wherein choosing a "vantage" yields a theory which is consistent, but the entire theory may not be consistent? I don't really know how to formalize this question, but my intuition is that vantages are like objects in a category, and looking at the theory from a vantage amounts to something like passing to the slice category. Maybe one way to formalize this is in terms of locally cartesian closed $n$-categories?

I imagine it would be interesting to have a system which coheres globally, but has "holes" in it. One can still perform deductions from individual vantages, but to compare local theorems one must choose a consistent "path" between vantages that facilitates the transport of theorems. Clearly there is a strong geometric analogy here.

I apologize if this is not appropriate for MathOverflow, but I wanted to pick the brains of researchers in logic and model theory to get as enlightening answers as possible. Thank you.

$\endgroup$
3
  • 1
    $\begingroup$ "Relevant logic" answers your question, especially for non-mathematical theories. $\endgroup$
    – user44143
    Commented Dec 22, 2016 at 18:47
  • 4
    $\begingroup$ For contrast and clarity, check out compactness for logical systems, where for first order logic a theory (set of sentences is consistent iff every finite subset is) is not just locally consistent. Gerhard "Not All Logics Are Compact" Paseman, 2016.12.22. $\endgroup$ Commented Dec 22, 2016 at 18:50
  • $\begingroup$ Thank you both for your comments, this gives me a good starting place! $\endgroup$ Commented Dec 22, 2016 at 18:58

0

You must log in to answer this question.

Browse other questions tagged .