Full Idea
A non-trivial individual essence is properties other than a) those following from a de dicto truth, b) properties of existence and self-identity (or their cognates), c) properties derived from necessities in some other category.
Gist of Idea
Non-trivial individual essence is properties other than de dicto, or universal, or relational
Source
Graeme Forbes (The Metaphysics of Modality [1985], 5.1)
Book Reference
Forbes,Graeme: 'The Metaphysics of Modality' [OUP 1985], p.99
A Reaction
[I have compressed Forbes] Rather than adding all these qualificational clauses to our concept, we could just tighten up on the notion of a property, saying it is something which is causally efficacious, and hence explanatory.