Full Idea
We understand subjunctive conditionals as statements about possibilities, excluding those actualised. So that form is just right for part of the analysis of a power statement, since to say a thing has a power is to say what behaviour is possible for it.
Clarification
'subjunctive conditionals' are nowadays usually just known as 'counterfactuals'
Gist of Idea
Counterfactuals are just right for analysing statements about the powers which things have
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 5.VII)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.98
A Reaction
They seem unaware of the famous work of Stalnaker and Lewis on this type of analysis, but as a fan of powers I find this interesting, and it offers a nice extra piece for my big jigsaw.