Lewisian analysis of objective probability: An origin of the undermining futures

Abstract

David Lewis? interpretation of objective probability has two essential parts: Humean supervenience and Best system of laws. According to his interpretation, probabilities, along with the other nomic phenomena, supervene on the actual facts. Lewis also famously formulated the Principal Principle, which should show the connection between objective and subjective probabilities. However, years later, Hall, Thau and Lewis himself came to conclusion that the principle and Lewis? interpretation of probability are not compatible. The main reason for that is the problem of so called undermining futures: Lewis named the problem ?Big Bad Bug?. A popular way to solve the problem was to change the principal principle. In this article, I will argue that the origin of the problem is not compatibility of the principle and Lewis?s interpretation of probability, but that the problem is in the interpretation itself. Changing the principle, I argue, will not conclusively solve the problem.