SELF-REFERENCE IN ARITHMETIC II

Abstract

AbstractIn this sequel to Self-reference in arithmetic I we continue our discussion of the question: What does it mean for a sentence of arithmetic to ascribe to itself a property? We investigate how the properties of the supposedly self-referential sentences depend on the chosen coding, the formulae expressing the properties and the way a fixed point for the expressing formulae are obtained. In this second part we look at some further examples. In particular, we study sentences apparently expressing their Rosser-provability, their own ${\rm{\Sigma }}_n^0$-truth or their own ${\rm{\Pi }}_n^0$-truth. Finally we offer an assessment of the results of both papers.