Full Idea
Fragility is not a fundamental physical property, in that two pieces of glass cannot be physically identical save for their fragility.
Gist of Idea
A property is fundamental if two objects can differ in only that respect
Source
Tim Maudlin (The Metaphysics within Physics [2007], 2.5)
Book Reference
Maudlin,Tim: 'The Metaphysics within Physics' [OUP 2007], p.72
A Reaction
Nice. The best idea I have found in Maudlin, so far! This gives a very nice test for picking out the fundamental physical and intrinsic properties.