Possible Worlds

Possible worlds’ semantics for modal logic has proven to be theoreti- cally useful. But talk of possible worlds is puzzling. After all, what are possible worlds? This essay provides an overview of two of the main theories on the nature of possible worlds, namely, Lewis’s Extreme Realism and Plantinga and Stalnaker’s Moderate Realism. The essay also explores the merits and shortcomings of both theories.Fundação para a Ciência e a Tecnologi