Classical predicative logic-enriched type theories

A logic-enriched type theory (LTT) is a type theory extended with a primitive mechanism for forming and proving propositions. We construct two LTTs, named LTT0 and LTT 0, which we claim correspond closely to the classical predicative systems of second order arithmetic ACA0 and ACA. We justify this claim by translating each second-order system into the corresponding LTT, and proving that these translations are conservative. This is part of an ongoing research project to investigate how LTTs may be used to formalise different approaches to the foundations of mathematics. The two LTTs we construct are subsystems of the logic-enriched type theory LTTW, which is intended to formalise the classical predicative foundation presented by Herman Weyl in his monograph Das Kontinuum. The system ACA0 has also been claimed to correspond to Weyl's foundation. By casting ACA0 and ACA as LTTs, we are able to compare them with LTTW. It is a consequence of the work in this paper that LTTW is strictl...

• Type: Journal
• Year: 2010
• Where: APAL
• Authors: Robin Adams, Zhaohui Luo
• Keywords: APAL 2010, Classical Predicative Systems, Logic-enriched Type Theory, Type Theory