This volume is an exploration of the ways in which the notion of possible worlds has been used in recent philosophy and logic. There is a bias towards looking at the topics from a philosophical logic perspective. Although this book is intended for the wider audience, it is written with an eye to making the topics readily available to senior undergraduates and postgraduates. I begin with the ways in which possible worlds have been used as a framework for considering problems in logic and argument analysis. There are chapters that introduce the absolutely minimal amount of logic required for a logical perspective on possible worlds. These are followed by chapters with possible worlds and modal logic based discussions of questions of meaning, epistemic possibility, temporal logic, metaphysics and impossibility. The focus has been on underlying assumptions and doctrines, rather than on the consequential problems that come out of alleged solutions. It is quite surprising to find in some areas that, although the writers base their work on modal logic, very little use is actually made of possible worlds. Again and again I have come back to the questions of existence, quantification and impossibility. The text is deliberately, and perhaps rashly, provocative. I hope it will provide a good stepping-off point for vigorous discussion.