On Feferman's operational set theory OST

We study OST and some of its most important extensions primarily from a proof-theoretic perspective, determine their consistency strengths by exhibiting equivalent systems in the realm of traditional set theory and introduce a new and interesting extension of OST which is conservative over ZFC.

• Type: Journal
• Year: 2007
• Where: APAL
• Authors: Gerhard Jäger
• Keywords: APAL 2007, Important Extensions, Proof-theoretic Perspective, Traditional Set Theory