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.

This book analyses the debate over extraterrestrial life from Aristotle to Kant.

Challenging the thesis that there is only one world, the author builds on Immanuel Kant's notion of metaphysical inversion to develop his idea that a world is the sum total of what exists in a particular time. In arguing that there are many representing beings, actual worlds, and truths, the author addresses ontological questions raised by Protagoras, Plato, and numerous contemporary philosophers. He concludes that there is no social and political reality independent of perspective. Annotation copyrighted by Book News, Inc., Portland, OR

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.

Convention was immediately recognized as a major contribution to the subject and its significance has remained undiminished since its first publication in 1969. Lewis analyzes social conventions as regularities in the resolution of recurring coordination problems-situations characterized by interdependent decision processes in which common interests are at stake. Conventions are contrasted with other kinds of regularity, and conventions governing systems of communication are given special attention.