Full Idea
From the point of view of philosophical logic, the nature of a kind, or a material substance or an individual is its essence, that is, those of its qualities which are inseparable from its being that kind, that material or that individual.
Gist of Idea
In logic the nature of a kind, substance or individual is the essence which is inseparable from what it is
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 6.I)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.101
A Reaction
This might be where the logical and the naturalistic notions of essence come apart. Could something retain its 'natural' essence while losing its identity, or lose its essence while retaining its identity?