Full Idea
Essentialism is the view that categories have an underlying reality or true nature that one cannot observe directly but that gives an object its identity.
Gist of Idea
Essentialism says categories have a true hidden nature which gives an object its identity
Source
Susan A. Gelman (The Essential Child [2003], 01 'Intro')
Book Reference
Gelman,Susan A.: 'The Essential Child' [OUP 2005], p.3
A Reaction
I think the introduction of categories here is a misunderstanding. Does an uncategorisable thing therefore have no identity (even though it has properties)? If categories give objects their identity, what gives categories their identity?