The Elusiveness of Disquotationalism

An axiomatization (or theory or 'implicit definition') of truth is called disquotational iff it can be given by a set of sentences of the form

'A' is true iff A

and no further truth-theoretic sentences.

The discussion of the formal properties of disquotational theories has focused on axiomatizations where A is assumed not to contain the truth predicate. I'll argue that, while Tarski might have had good reasons for this restriction, the disquotationalist should look at more liberal versions. The resulting theories differ widely in their formal properties.

I'll look at the disquotational theory PUTB (Axiomatic Theories of Truth, Cambridge University Press, 2011, Chapter 19), which refutes the often held view that disquotational theories are deductively weak. PUTB is deductively as strong as the Kripke-Feferman theory.

I take a pessimistic view on disquotationalism: without a policy on the permissible instances it is a vacuous doctrine, but I don't think that a sensible policy has been found.

If time permits, I'll discuss the role of the T-sentences in Tarski's account and show why Tarski's use of the T-sentences contradicts his discussion of disquotational theories.