We prove a conservativity result for extensional type theories over propositional ones, i.e. dependent type theories with propositional computation rules, or computation axioms, using insights from homotopy type theory. The argument exploits a notion of canonical homotopy equivalence between contexts, and uses the notion of a category with attributes to phrase the semantics of theories of dependent types. Informally, our main result asserts that, for judgements essentially concerning h-sets, reasoning with extensional or propositional type theories is equivalent.

@article{paperbot3370,
  title = {Relating homotopy equivalences to conservativity in dependent type theories with computation axioms},
  author = {Matteo Spadetto},
  journal = {Logical Methods in Computer Science},
  volume = {Volume 21, Issue 3},
  year = {2025},
  doi = {10.46298/lmcs-21(3:32)2025}
}