Lewisian Genuine Realism about possible worlds is often deemed unable to accommodate impossible worlds and reap the benefits that these bestow to rival theories. This thesis explores two alternative extensions of GR into the terrain of impossible worlds. It is divided in six chapters. Chapter I outlines Lewis’ theory, the motivations for impossible worlds, and the central problem that such worlds present for GR: How can GR even understand the notion of an impossible world, given Lewis’ reductive theoretical framework? Since (...) the desideratum is to incorporate impossible worlds into GR without compromising Lewis’ reductive analysis of modality, Chapter II defends that analysis against objections. The rest of the thesis is devoted to incorporating impossible worlds into GR. Chapter III explores GR-friendly impossible worlds in the form of set-theoretic constructions out of genuine possibilia. Then, Chapters IV-VI venture into concrete impossible worlds. Chapter IV addresses Lewis’ objection against such worlds, to the effect that contradictions true at impossible worlds amount to true contradictions tout court. I argue that even if so, the relevant contradictions are only ever about the non-actual, and that Lewis’ argument relies on a premise that cannot be nonquestion- beggingly upheld in the face of genuine impossible worlds in any case. Chapter V proposes that Lewis’ reductive analysis can be preserved, even in the face of genuine impossibilia, if we differentiate the impossible from the possible by means of accessibility relations, understood non-modally in terms of similarity. Finally, Chapter VI counters objections to the effect that there are certain impossibilities, formulated in Lewis’ theoretical language, which genuine impossibilia should, but cannot, represent. I conclude that Genuine Realism is still very much in the running when the discussion turns to impossible worlds. (shrink)

In her (1996) Kadri Vihvelin argues that autoinfanticide is nomologically impossible and so that there is no sense in which time travelers are able to commit it. In response, Theodore Sider (2002) defends the original Lewisian verdict (Lewis 1976) whereby, on a common understanding of ability, time travelers are able to kill their earlier selves and their failure to do so is merely coincidental. This paper constitutes a critical note on arguments put forward by both Sider and Vihvelin. I argue (...) that although Sider’s criticism starts out promisingly he doesn’t succeed in establishing that Vihvelin’s analysis fails, because (a) he neglects to rule out a class of counterfactuals to which Vihvelin’s sample-case may belong; and (b) (together with Lewis) he is wrong to suggest that future facts are irrelevant in the evaluation of time travelers’ abilities. I show instead that Vihvelin’s argument is viciously circular, indicating that even if there are nomological constraints on autoinfanticide these cannot be established a priori. (shrink)

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. (shrink)