Full Idea
Described as a man it is quite contingent that he has a child, but described as a father it is conceptually necessary that he has a child. But that conceptual necessity is a reflection of the natural necessity of the father's role in reproduction.
Gist of Idea
Having a child is contingent for a 'man', necessary for a 'father'; the latter reflects a necessity of nature
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 3.I)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.48
A Reaction
This is a (good) response to Quine's claim that necessity depends entirely on the mode of description (and his mathematician cyclist example).
Related Idea
Idea 8482 Mathematicians must be rational but not two-legged, cyclists the opposite. So a mathematical cyclist? [Quine]