Full Idea
When discoveries about the nature of a thing or substance explain or justify our holding that certain properties are its nominal essence, then the diachronic process of meaning development creates a genuine conceptual necessity.
Clarification
'diachronic' means over a period of time
Gist of Idea
There is a conceptual necessity when properties become a standard part of a nominal essence
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 1.VI)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.22
A Reaction
This sounds like a pretty good account of one of the bases for conceptual necessity. They seem to think that conceptual necessity rests on a mixture of real and nominal essence (but then some of the nominal features are also real).
Related Ideas
Idea 15233 If natural necessity is used to include or exclude some predicate, the predicate is conceptually necessary [Harré/Madden]
Idea 12531 Nominal Essence is the abstract idea to which a name is attached [Locke]