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Full Idea
In semantic theories (e.g.Tarski's or Kripke's), a definition evades Tarski's Theorem by restricting the possible instances in the schema T[φ]↔φ to sentences of a proper sublanguage of the language formulating the equivalences.
Gist of Idea
Semantic theories avoid Tarski's Theorem by sticking to a sublanguage
Source
Volker Halbach (Axiomatic Theories of Truth [2011], 1)
Book Ref
Halbach,Volker: 'Axiomatic Theories of Truth' [CUP 2011], p.6
A Reaction
The schema says if it's true it's affirmable, and if it's affirmable it's true. The Liar Paradox is a key reason for imposing this restriction.
Related Idea
Idea 16295 Tarski proved that truth cannot be defined from within a given theory [Tarski, by Halbach]
| 19188 | We can't use a semantically closed language, or ditch our logic, so a meta-language is needed [Tarski] |
| 19189 | The metalanguage must contain the object language, logic, and defined semantics [Tarski] |
| 23297 | The language to define truth needs a finite vocabulary, to make the definition finite [Davidson] |
| 23288 | When Tarski defines truth for different languages, how do we know it is a single concept? [Davidson] |
| 19323 | 'Snow is white' depends on meaning; whether snow is white depends on snow [Etchemendy] |
| 15345 | Semantic theories have a regress problem in describing truth in the languages for the models [Horsten] |
| 16297 | Semantic theories avoid Tarski's Theorem by sticking to a sublanguage [Halbach] |
| 15649 | In semantic theories of truth, the predicate is in an object-language, and the definition in a metalanguage [Halbach] |
| 19120 | Semantic theories need a powerful metalanguage, typically including set theory [Halbach/Leigh] |