Full Idea
The metaphysical doctrine of essentialism says that certain properties of things are properties that those things could not fail to have, except by not existing.
Gist of Idea
Essentialism says some properties must be possessed, if a thing is to exist
Source
Nathan Salmon (Reference and Essence (1st edn) [1981], 3.8.2)
Book Reference
Salmon,Nathan: 'Reference and Essence (2nd ed)' [Prometheus 2005], p.82
A Reaction
A bad account of essentialism, and a long way from Aristotle. It arises from the logicians' tendency to fix objects entirely in terms of a 'flat' list of predicates (called 'properties'!), which ignore structure, constitution, history etc.