Physics and the Humean approach to Probability

© The several contributors 2011. All rights reserved. This chapter defends a Humean approach to objective probabilities in physics. Two motivations for a Humean account of probabilities are distinguished: One derives from a general commitment to a Humean account of natural laws. The other, which is articulated in more detail in the chapter, starts from worries that irreducibly probabilistic physical laws are problematic. Such worries are avoided if probabilities are tied to a best system of the world, as D. Lewis has suggested. Lewis' own account of objective chance is contrasted with a more pragmatic Humean account, in which objective probabilities are divorced from the best system and tied to systems of less simple probability rules instead. The chapter compares the abilities of both Humean accounts to capture the probabilities appearing in our best physical theories.