Full Idea
By holding that the most unified beings have essences in an unqualified sense, while allowing that other beings have them in a qualified sense - we can think of unity as a matter of degree.
Gist of Idea
If unity is a matter of degree, then essence may also be a matter of degree
Source
Charlotte Witt (Substance and Essence in Aristotle [1989], 4.3)
Book Reference
Witt,Charlotte: 'Substance and Essence in Aristotle' [Cornell 1994], p.121
A Reaction
This is Witt's somewhat unorthodox view of how we should read Aristotle. I am sympathetic, if essences are really explanatory. That means they are unstable, and would indeed be likely to come in degrees.