In a previous question, I asked something similar but without explicitely referring to the source material of my doubt. Now I try to state it here with more precision: In "Non-catastrophic presupposition failure" Yablo tries to argue why sometimes, even if a presupposition is false, some statements strike us as true or false, and not undefined.
For instance: "The king of France is Bald & the Queen of England is bald" strikes us as false, even though there is no king of France. A possibile reason might be that the statement would be false, even if there was a king of France. In order to illustrate this possibility, Yablo writes:
The real asserted content S of a sentence, when a presupposition is false, is true(false) iff the simple sentence S is true(false) in the closest possibile world where the presupposition P holds.
From the paper: "S is true (false) in w iff S is true (false) in the world closest to w where π holds."
Given the previous example, "KoF is balde and QoE is bald" strikes us as false because, in the closest possibile world in which there is a king of France, that sentence is false, due to the fact that the Queen of England is not bald.
then Yablo goes on and says:
"This simplifies matters, because for S to be true (false) in the world closest to w where π holds is, on standard theories of conditionals, precisely what it takes for a conditional π → S to be true (false) in w."
"S is true (false) in w iff π → S is true (false) in w." "Note 22: I assume that π→S is false iff π→~S is true."
This looks to me as Yablo is putting forth the fact that "being true in the closest possible world where π is true" can be identified with π → S being true in the world of interest (where the evaluation takes place, so to speak) - but it is not clear to me why it should be so.