Full Idea
The muon has mass 106.2 MeV, unit negative charge, and spin a half. The electron and tauon have unit negative charge, but electrons are 200 times less massive, and tauons 17 times more massive. Its essential properties are not mutually entailing.
Gist of Idea
One essential property of a muon doesn't entail the others
Source
George Molnar (Powers [1998], 2.1)
Book Reference
Molnar,George: 'Powers: a study in metaphysics', ed/tr. Mumford,Stephen [OUP 2003], p.51
A Reaction
This rejects a popular idea of scientific essentialism, that the essence is the set of properties which entail the non-essential properties (and not vice versa), a view which I had hitherto found rather appealing.