Full Idea
It is wrong to say that there is any one theory of truth, for truth is not a concept.
Gist of Idea
There is no theory of truth, because it isn't a concept
Source
Ludwig Wittgenstein (Lectures 1930-32 (student notes) [1931], C V B)
Book Reference
Wittgenstein,Ludwig: 'Lectures in Cambridge 1930-32', ed/tr. Lee,Desmond [Blackwell 1980], p.75
A Reaction
This makes you wonder how he understood the word 'concept'. In most modern discussions truth seems to be a concept, and in Frege it can be an unsaturated predicate which is satisfied by sentences or thoughts.