Full Idea
We would never use 'is essentially' for 'is necessarily' where vacuous properties are concerned, as in 'Socrates is essentially snub-nosed' or 'Socrates is essentially Socrates'.
Gist of Idea
'Essentially' won't replace 'necessarily' for vacuous properties like snub-nosed or self-identical
Source
Ruth Barcan Marcus (Essential Attribution [1971], p.193)
Book Reference
-: 'Nous' [-], p.193
A Reaction
This simple point does us a huge service in rescuing the word 'essential' from several hundred years of misguided philosophy.