Full Idea
Being gold or being a man is not accidental. ..Such essences are dispositional properties of a very special kind: if an object had such a property and ceased to have it, it would have ceased to exist or have changed (as if gold is transmuted to lead).
Gist of Idea
Dispositional essences are special, as if an object loses them they cease to exist
Source
Ruth Barcan Marcus (Essential Attribution [1971], p.202)
Book Reference
-: 'Nous' [-], p.202
A Reaction
Ruth Marcus is an important founder of modern scientific essentialism, by not only proposing the notion we call rigid designation, but by explicitly defending the essential identities that seem to emerge from modal logic.