Full Idea
'All humans who live in houses with prime house numbers are mortal' is not a law because the class referred to is not a natural kind.
Gist of Idea
'Humans with prime house numbers are mortal' is not a law, because not a natural kind
Source
Tim Maudlin (The Metaphysics within Physics [2007], 1.6)
Book Reference
Maudlin,Tim: 'The Metaphysics within Physics' [OUP 2007], p.36
A Reaction
Maudlin wants laws to be primitive, but he now needs a primitive notion of a natural kind to make it work. If kinds generate laws, you can ditch the laws, and build your theory on the kinds. He also says no death is explained by 'all humans are mortal'.