We provide infinitary proof theories for three common semantic theories of truth: strong Kleene, van Fraassen supervaluation and Cantinisupervaluation. The value of these systems is that they provide an easy method of proving simple facts about semantic theories. Moreover we shall show that they also give us a simpler understanding of the computational complexity of these definitions and provide a direct proof that the closure ordinal for Kripke’s definition is ωCK1. This work can be understood as an effort to provide a proof-theoretic counterpart to Welch’s game theoretic (Welch, 2009).
- Semantic Theories of Truth