Full Idea
So-called 'Aristotelian essentialism' is the doctrine of essences not relative to specifications.
Gist of Idea
Aristotelian essentialism says essences are not relative to specification
Source
David Lewis (Counterpart theory and Quant. Modal Logic [1968], III)
Book Reference
Lewis,David: 'Philosophical Papers Vol.1' [OUP 1983], p.32
A Reaction
In other words, they are so-called 'real essences', understood as de re. Quine says essences are all de dicto, and relative to some specification. I vote for Aristotle.