Full Idea
The purpose of the antecedent of a counterfactual is to provide instructions on how to pick a Cauchy surface (pick a moment in time) and how to generate an altered description of that moment. It is more of a command than an indicative sentence.
Gist of Idea
A counterfactual antecedent commands the redescription of a selected moment
Source
Tim Maudlin (The Metaphysics within Physics [2007], 1.5)
Book Reference
Maudlin,Tim: 'The Metaphysics within Physics' [OUP 2007], p.23
A Reaction
Quite plausible, but the antecedent might contain no description. 'If things had gone differently, we wouldn't be in this mess'. The antecedent might be timeless. 'If pigs had wings, they still wouldn't fly'.