Full Idea
The generalisation 'What makes a (any) sentence true?' is not a request for definitions of 'true' (the concept), but rather requests for (partial) explanations of why certain particular sentences are true.
Gist of Idea
We want to know what makes sentences true, rather than defining 'true'
Source
Ian McFetridge (Truth, Correspondence, Explanation and Knowledge [1977], II)
Book Reference
McFetridge,Ian G.: 'Logical Necessity' [Aristotelian Soc 1990], p.38
A Reaction
McFetridge is responding to the shortcomings of Tarski's account of truth. The mystery seems to be why some of our representations of the world are 'successful', and others are not.