Full Idea
The new essentialism retains Aristotelian ideas about essential properties, but it distinguishes more clearly between 'individual essences' and 'kind essences'; the former define a particular individual, the latter what kind it belongs to.
Gist of Idea
'Individual essences' fix a particular individual, and 'kind essences' fix the kind it belongs to
Source
Brian Ellis (The Philosophy of Nature: new essentialism [2002], Ch.1)
Book Reference
Ellis,Brian: 'The Philosophy of Nature: new essentialism' [Acumen 2002], p.12
A Reaction
This might actually come into conflict with Aristotle, who seems to think that my personal essence is largely a human nature I share with everyone else. The new distinction is trying to keep the Kantian individual on the stage.