Full Idea
The possibility of a consistent use of 'true sentence' which is in harmony with the laws of logic and the spirit of everyday language seems to be very questionable, so the same doubt attaches to the possibility of constructing a correct definition.
Gist of Idea
'True sentence' has no use consistent with logic and ordinary language, so definition seems hopeless
Source
Alfred Tarski (The Concept of Truth for Formalized Languages [1933], §1)
Book Reference
Tarski,Alfred: 'Logic, Semantics, Meta-mathematics' [Hackett 1956], p.165
A Reaction
This is often cited as Tarski having conclusively proved that 'true' cannot be defined from within a language, but his language here is much more circumspect. Modern critics say the claim depends entirely on classical logic.