Full Idea
If fragile means nothing more than 'breaks when dropped', then it is no explanation of why something breaks when dropped.
Gist of Idea
If fragile just means 'breaks when dropped', it won't explain a breakage
Source
Stephen Mumford (Dispositions [1998], 06.5)
Book Reference
Mumford,Stephen: 'Dispositions' [OUP 1998], p.134
A Reaction
His point is that you have to unpack the notion of fragile, which presumably cites underlying mechanisms. This is the 'virtus dormitiva' problem - but that explanation of opium's dormitive powers is not entirely stupid.