Full Idea
The point of the essentialist theory is not to provide a reductive explanation of necessities. It is, rather, to locate a base class of necessities - those which directly reflect the natures of things - in terms of which the remainder may be explained.
Gist of Idea
Essentialism doesn't explain necessity reductively; it explains all necessities in terms of a few basic natures
Source
Bob Hale (Necessary Beings [2013], 06.6)
Book Reference
Hale,Bob: 'Necessary Beings' [OUP 2013], p.158
A Reaction
My picture is of most of the necessities being directly explained by the natures of things, rather than a small core of natures generating all the derived ones. All the necessities of squares derive from the nature of the square.