Full Idea
To attribute necessity to a condition, an outcome or effect, the truth of a statement, or a conclusion, is to indicate within the relevant context that no alternative is possible. In each context there are appropriate grounds for such judgements.
Gist of Idea
We say there is 'no alternative' in all sorts of contexts, and there are many different grounds for it
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 1.V)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.19
A Reaction
This anticipipates Kit Fine's account of necessity by 25 years, and seems to be the right way to understand it. In ordinary usage, 'there is no alternative' is obvious a quite different claim in very different contexts.