Intertheoretic Reduction

Abstract

We reconsider the Generalized Nagel-Schaffner (GNS) model of reduction and argue that, contrary to a widely held view, it is the right analysis of intertheoretic reduction. In particular, it provides a convincing analysis of the reductive relationship between statistical mechanics and thermodynamics. Then we proceed to a Bayesian analysis of the epistemic value of reduction, showing that intertheoretic (GNS) reduction facilitates flow of confirmation between the reducing and the reduced theory. Specifically, we show that evidence which prior to reduction supported only one of the theories, comes to support the other theory as well. Moreover, a successful reduction increases both the prior and posterior probability of the conjunction of both theories.