Full Idea
Essentialists say that dispositional properties may be fundamental, whereas for a passivist such qualities are not primary, but supervene on the primary qualities of matter, and on the laws of nature.
Clarification
'Passivists' thing objects are passive, and natural laws are imposed on them
Gist of Idea
Essentialists say dispositions are basic, rather than supervenient on matter and natural laws
Source
Brian Ellis (The Philosophy of Nature: new essentialism [2002], Ch.3)
Book Reference
Ellis,Brian: 'The Philosophy of Nature: new essentialism' [Acumen 2002], p.48
A Reaction
I am strongly in favour of this view of nature. Without essentialism, we have laws of nature arising out of a total void (or God), and arbitrarily imposing themselves on matter. What are the 'primary qualities of matter', if not dispositions?