To make firsthand use of modal expressions / subjunctive conditionals, is to be about the business of explaining a state of affairs or justifying an assertion.

Counterfactuals, Dispositions, and the Causal Modalities §80

Keep in mind the “argument types” of explanation and justification.

  • We explain an (actual) state of affairs.
  • We justify an assertion (non-actual, in the space of reasons).