Full Idea
If one were asked 'What makes salt soluble in water?', the most natural answer would be something of the style 'The fact that it has such-and-such structure'.
Gist of Idea
We normally explain natural events by citing further facts
Source
Ian McFetridge (Truth, Correspondence, Explanation and Knowledge [1977], II)
Book Reference
McFetridge,Ian G.: 'Logical Necessity' [Aristotelian Soc 1990], p.39
A Reaction
Personally I would want to talk about its 'powers' (dispositional properties), rather than its 'structure' (categorical properties). This defends facts, but you could easily paraphrase 'fact' out of this reply (as McFetridge realised).