 The third argument is from counterpossible reasoning. Suppose, in a class on alternative logics, we consider what would happen if Excluded Middle \((\vDash A \vee \neg A)\), Double-Negation Elimination \((\neg \neg A \vDash A)\), or the Law of Explosion \((A, \neg A \vDash B)\) were to fail. If classical logic is the one true logic, and logical necessity is absolute, we’re then reasoning counterpossibly. If we want to analyse counterpossibles in general using impossible worlds, then we’ll need worlds where these principles fail. But we seem to be able to reason this way, non-trivially, for any kind of logical principle, and so our analysis will require open worlds (Priest 2016).