Full Idea
The relationship between co-existing properties or successive events or states is naturally necessary when understood by scientists to be related by generative mechanisms, whose structure and components constitute the essential natures of the world.
Gist of Idea
Property or event relations are naturally necessary if generated by essential mechanisms
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 7.III)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.130
A Reaction
Does that mean that the relationship between an actual state and a possible state is metaphysically necessary, rather than naturally necessary? I think we need dispositions to be part of actuality, and hence replace 'co-existing' with 'possible'.