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.

Science Without Numbers caused a stir in 1980, with its bold nominalist approach to the philosophy of mathematics and science. It has been unavailable for twenty years and is now reissued in a revised edition with a substantial new preface presenting the author's current views and responses to the issues raised in subsequent debate.

Fictionalism about possible worlds is the view that talk about worlds in the analysis of modality is to be construed as ontologically innocent discourse about the content of a fiction. Versions of the view have been defended by D M Armstrong (in "A Combinatorial Theory of Possibility") and by myself (in "Modal Fictionalism', "Mind" 99, July 1990). The present note argues that fictionalist accounts of modality (both Armstrong's version and my own) fail to serve the fictionalists ontological purposes because they (...) imply that as a matter of necessity there exist many worlds. (shrink)

Modal functionalism is the view that talk about possible worlds should be construed as talk about fictional objects. The version of modal fictionalism originally presented by Gideon Rosen adopted a simple prefixing strategy for fictionalising possible worlds analyses of modal propositions. However, Stuart Brock and Rosen himself in a later article have independently advanced an objection that shows that the prefixing strategy cannot serve fictionalist purposes. In this paper we defend fictionalism about possible worlds by showing that there are other (...) strategies besides the prefixing strategy for fictionalising talk about possible worlds, and that these strategies are proof against the objection advanced by Brock and Rosen. (shrink)