This book is a defense of modal realism; the thesis that our world is but one of a plurality of worlds, and that the individuals that inhabit our world are only a few out of all the inhabitants of all the worlds. Lewis argues that the philosophical utility of modal realism is a good reason for believing that it is true.

The best arguments for possible worlds as states of affairs furnish us with equally good arguments for impossible worlds of the same sort. I argue for a theory of impossible worlds on which the impossible worlds correspond to maximal inconsistent classes of propositions. Three objections are rejected. In the final part of the paper, I present a menu of impossible worlds and explore some of their interesting formal properties.

Paraconsistent logics are often semantically motivated by considering "impossible worlds." Lewis, in "Logic for equivocators," has shown how we can understand paraconsistent logics by attributing equivocation of meanings to inconsistent believers. In this paper I show that we can understand paraconsistent logics without attributing such equivocation. Impossible worlds are simply sets of possible worlds, and inconsistent believers (inconsistently) believe that things are like each of the worlds in the set. I show that this account gives a sound and complete semantics (...) for Priest's paraconsistent logic LP, which uses materials any modal logician has at hand. (shrink)

This book, one of the first full-length studies of the modalities to emerge from the debate to which Saul Kripke, David Lewis, Ruth Marcus, and others are contributing, is an exploration and defense of the notion of modality de re, the idea that objects have both essential and accidental properties. Plantinga develops his argument by means of the notion of possible worlds and ranges over such key problems as the nature of essence, transworld identity, negative existential propositions, and the existence (...) of unactual objects in other possible worlds. He also applies his logical theories to the elucidation of two problems in the philosophy of religion: the problem of evil and the ontological argument. (shrink)

William G. Lycan; XII*—Two—No, Three—Concepts of Possible Worlds, Proceedings of the Aristotelian Society, Volume 91, Issue 1, 1 June 1991, Pages 215–228, https.

Counterfactuals is David Lewis' forceful presentation of and sustained argument for a particular view about propositions which express contrary to fact conditionals, including his famous defense of realism about possible worlds and his theory of laws of nature.

The paper contains a short story which is inconsistent, essentially so, but perfectly intelligible. The existence of such a story is used to establish various views about truth in fiction and impossible worlds.

A theory of ersatz impossible worlds is developed to deal with the problem of counterpossible conditionals. Using only tools standardly in the toolbox of possible worlds theorists, it is shown that we can construct a model for counterpossibles. This model is a natural extension of Lewis's semantics for counterfactuals, but instead of using classical logic as its base, it uses the logic LP.

In this dissertation, I critically investigate the usefulness of impossible worlds in the analysis of various modal concepts. I argue that we have reason to adopt analyses that appeal to impossible worlds of a very conservative variety, but that we should reject analyses that appeal to radically impossible worlds, or worlds where some classical contradictions are true. ;I begin by presenting and motivating two theories of possible worlds. These views are two of the most prominent and widely accepted conceptions of (...) worlds, the first being the conception most famously endorsed by David Lewis , the second being the conception most famously endorsed by Alvin Plantinga . I next present and motivate two theories that posit both possible and impossible worlds. The first is a view suggested by Takashi Yagisawa , the second is a view often attributed to William Lycan . These latter two views are extensions of the former two views in that they take the existing Lewis and Plantinga frameworks and add impossible worlds of the same basic kind . ;I then present and critically discuss what I take to be the criteria that must be satisfied by any theory of worlds in order for it be counted as adequate. Each of the four worlds theories under consideration are evaluated with respect to these criteria; viz., plausibility of ontology, ability to accommodate core modal concepts, and ability to provide analyses of non-core modal concepts. I argue extensively for the claim that, given the particular failures of each of the four views with respect to these criteria, none should be regarded as adequate. ;In the concluding chapter, I suggest and endorse a new sort of worlds view: one that extends the Plantingean conception, but adds impossible worlds of an ultra-conservative variety. This theory of metaphysically impossible---but logically possible---worlds, I argue, comes closest to satisfying all of the criteria for adequacy. (shrink)