Full Idea
The truthmaker principle seems compelling, because if a proposition is true, something must be different from a world in which it is false. The principle makes this specific, by treating 'something' as a quantifier binding a variable in name position.
Gist of Idea
The truthmaker principle requires some specific named thing to make the difference
Source
Timothy Williamson (Truthmakers and Converse Barcan Formula [1999], §2)
Book Reference
-: 'Dialectica' [-], p.257
A Reaction
See Williamson for an examination of the logical implications of this. The point is that the principle seems to require some very specific 'thing', which may be asking too much. For a start, it might be the absence of a thing.