Abstract

David Lewis famously dismisses genuine impossible worlds on the basis that a contradiction bound within the scope of his modifier ‘at w’ amounts to a contradiction tout court—an unacceptable consequence. Motivated by the rising demand for impossible worlds in philosophical theorising, this paper examines whether anything coherent can be said about an extension of Lewis’ theory of genuine, concrete possible worlds into genuine, concrete impossible worlds. Lewis’ reasoning reveals two ways to carve out conceptual space for the genuinely impossible. The first is to abandon Lewis’ classical translation schema for negation, on the basis that it begs the question against incomplete and inconsistent worlds. I argue that, whilst this option incurs some loss in the semantics, it preserves the core spirit of Lewis’ metaphysics. The alternative is to bite the bullet, abandon classical logic and embrace true contradictions. The key challenge with this strategy is that the resulting theory seems committed to a particularly strong kind of dialethism—one that even dialethists would be reluctant to accept. I motivate such a dialethic account of genuine impossibilia using Lewis’ own methodology and defend it against triviality objections. I close with a few comments on why impossible worlds should not be reduced to set theoretic constructs out of possible worlds.