Abstract

The metaphysical theory of possible worlds has played a central role in contemporary philosophical discourse, with Modal Realism, particularly as developed by David Lewis, offering one of the most rigorous and provocative frameworks for understanding modality, necessity, and possibility. This paper provides an in-depth review of Modal Realism, exploring its ontological implications, its formalization within modal logic, and its relationship to probability theory. Special attention is given to counterfactuals, the interpretation of modal statements, and the mathematical underpinnings that structure our understanding of possible worlds. We also examine alternative views to Modal Realism, including actualism and essentialism, and consider the broader implications of possible worlds for metaphysics, epistemology, and the philosophy of science.