# On Natural Deduction for Herbrand Constructive Logics II: Curry-Howard Correspondence for Markov's Principle in First-Order Logic and Arithmetic

LIPICS - Leibniz International Proceedings in Informatics, Oct 2018

Intuitionistic first-order logic extended with a restricted form of Markov's principle is constructive and admits a Curry-Howard correspondence, as shown by Herbelin. We provide a simpler proof of that result and then we study intuitionistic first-order logic extended with unrestricted Markov's principle. Starting from classical natural deduction, we restrict the excluded middle and we obtain a natural deduction system and a parallel Curry-Howard isomorphism for the logic. We show that proof terms for existentially quantified formulas reduce to a list of individual terms representing all possible witnesses. As corollary, we derive that the logic is Herbrand constructive: whenever it proves any existential formula, it proves also an Herbrand disjunction for the formula. Finally, using the techniques just introduced, we also provide a new computational interpretation of Arithmetic with Markov's principle.

This is a preview of a remote PDF: http://drops.dagstuhl.de/opus/volltexte/2018/9859/pdf/LIPIcs-TYPES-2016-4.pdf

Federico Aschieri, Matteo Manighetti. On Natural Deduction for Herbrand Constructive Logics II: Curry-Howard Correspondence for Markov's Principle in First-Order Logic and Arithmetic, LIPICS - Leibniz International Proceedings in Informatics, 2018, 4:1-4:17, DOI: 10.4230/LIPIcs.TYPES.2016.4