 Given the limitations of Lewis-Stalnaker theories of counterfactual conditionals when dealing with impossible antecedents (see  §1.1.2),  it is natural to extend a theory of counterfactual conditionals with impossible worlds: see Routley (1989), Mares (1997), Nolan (1997), Brogaard and Salerno (2013). Similar theories can be offered of indicative conditionals: see Nolan (2016b).