Full Idea
If a classical language is expressively weakened - for example, by dispensing with negation - then it can contain its own truth predicate.
Gist of Idea
A weakened classical language can contain its own truth predicate
Source
Anil Gupta (Truth [2001], 5.2)
Book Reference
'Blackwell Guide to Philosophical Logic', ed/tr. Goble,Lou [Blackwell 2001], p.101
A Reaction
Thus the Tarskian requirement to move to a metalanguage for truth is only a requirement of a reasonably strong language. Gupta uses this to criticise theories that dispense with the metalanguage.
Related Ideas
Idea 16295 Tarski proved that truth cannot be defined from within a given theory [Tarski, by Halbach]
Idea 14796 Independent truth (if there is any) is the ultimate result of sufficient enquiry [Peirce]