Full Idea
Essences have normally been understood to be constituted by qualitative properties.
Gist of Idea
Essences are taken to be qualitative properties
Source
Robert Merrihew Adams (Primitive Thisness and Primitive Identity [1979], 1)
Book Reference
'Metaphysics - An Anthology', ed/tr. Sosa,E. /Kim,J. [Blackwell 1999], p.172
A Reaction
I add this simple point, because it might be challenged by the view that an essence is a substance, rather than the properties of anything. I prefer that, and would add that substances are individuated by distinctive causal powers.