Full Idea
When a natural necessity is used as the basis for the inclusion or exclusion of the appropriate predicate in the meaning of a concept of a kind of particular, then it is conceptually necessary that that kind of particular has that property or power.
Gist of Idea
If natural necessity is used to include or exclude some predicate, the predicate is conceptually necessary
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 1.V.B)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.20
A Reaction
This is one of the bolder views of Harré and Madden, since many philosophers would say that conceptual necessity rests entirely on convention rather than on nature. We could cut them out by just saying that most of our conventions rest on nature.
Related Idea
Idea 15235 There is a conceptual necessity when properties become a standard part of a nominal essence [Harré/Madden]