Full Idea
In each kind, whatever holds of something in itself and as such holds of it from necessity.
Gist of Idea
Whatever holds of a kind intrinsically holds of it necessarily
Source
Aristotle (Posterior Analytics [c.327 BCE], 75a30)
Book Reference
Aristotle: 'Posterior Analytics (2nd ed)', ed/tr. Barnes,Jonathan [OUP 1993], p.12
A Reaction
This seems to confirm the view that essential properties are necessary, but it does not, of course, follow that all necessary properties are essential properties (e.g. trivial necessities are not essential).