Editing T-schema (section)

{{Short description|Testing device for logical soundness}}
The '''T-schema''' ("truth [[schema (logic)|schema]]", not to be confused with "[[Convention T]]") is used to check if an [[inductive definition]] of truth is valid, which lies at the heart of any realisation of [[Alfred Tarski]]'s [[semantic theory of truth]]. Some authors refer to it as the "Equivalence Schema", a synonym introduced by [[Michael Dummett]].<ref name=Künne2005>{{cite book |last=Künne |first=Wolfgang |year=2003 |title=Conceptions of truth |publisher=Clarendon Press |isbn=978-0-19-928019-3 |page=[https://archive.org/details/conceptionsoftru0000kunn/page/18 18] |url=https://archive.org/details/conceptionsoftru0000kunn |url-access=registration}}</ref>

The T-schema is often expressed in [[natural language]], but it can be formalized in [[Predicate logic|many-sorted predicate logic]] or [[modal logic]]; such a formalisation is called a "'''T-theory'''."{{Citation needed|reason=I was not able to find a formalisation of the T-schema in either of the two references for this article. Please add references for the formalisation of the T-schema in predicate logic or in modal logic, preferably both.|date=October 2019}} T-theories form the basis of much fundamental work in [[philosophical logic]], where they are applied in several important controversies in [[analytic philosophy]].

As expressed in semi-natural language (where 'S' is the name of the sentence abbreviated to S): 'S' is true [[if and only if]] S.

Example: 'snow is white' is true if and only if snow is white.