The typed \(T\)-sentences are all equivalences of the form \(T\ulcorner \phi \urcorner \leftrightarrow \phi\), where \(\phi\) is a sentence not containing the truth predicate. Tarski (1935) called any theory proving these equivalences ‘materially adequate’. Tarski (1935) criticised an axiomatization of truth relying only on the \(T\)-sentences, not because he aimed at a definition rather than an axiomatization of truth, but because such a theory seemed too weak. Thus although the theory is materially adequate, Tarski thought that the \(T\)-sentences are deductively too weak. He observed, in particular, that the \(T\)-sentences do not prove the principle of completeness, that is, the sentence \(\forall{\scriptsize A}(T{\scriptsize A}\vee T[\neg{\scriptsize A}\)]) where the quantifier \(\forall{\scriptsize A}\) is restricted to sentences not containing T.