Full Idea
The central function of essence is to explain the actual existence of a unified substance.
Gist of Idea
Essences mainly explain the existence of unified substance
Source
Charlotte Witt (Substance and Essence in Aristotle [1989], 5 n1)
Book Reference
Witt,Charlotte: 'Substance and Essence in Aristotle' [Cornell 1994], p.144
A Reaction
She is offering an interpretation of Aristotle. Since existence is an active and not a passive matter, the identity of the entity will include its dispositions etc., I presume.