Full Idea
Essentialism for the class of concrete things is false, since a statue necessarily fulfils a condition as 'Goliath', but only contingently fulfils it as 'lumpl'. On the other hand, essentialism for the class of individual concepts can be true.
Clarification
'Lumpl' is his name for the piece of clay
Gist of Idea
Essentialism for concreta is false, since they can come apart under two concepts
Source
Allan Gibbard (Contingent Identity [1975], VII)
Book Reference
-: 'Journal of Symbolic Logic' [-], p.207
A Reaction
This rests on his definition of essentialism in Idea 14076. He rests his essentialism about concepts on an account given by Carnap ('Meaning and Necessity' §41). The essence of a statue and the essence of a lump of clay do seem distinct.
Related Idea
Idea 14076 Essentialism is the existence of a definite answer as to whether an entity fulfils a condition [Gibbard]