Unsound Inferences Make Proofs Shorter
arXiv:1608.07703 · doi:10.1017/jsl.2018.51
Abstract
We give examples of calculi that extend Gentzen's sequent calculus LK by unsound quantifier inferences in such a way that (i) derivations lead only to true sequents, and (ii) proofs therein are non-elementarily shorter than LK-proofs.
21 pages. July 2017 preprint