Abstract

In Newtonian physics, there is a clear distinction between a "framework theory", a collection of general physical principles and definitions of physical terms, and theories that describe specific causal interactions such as gravitation, i.e., "interaction theories". I argue that this distinction between levels of theory can also be found in the context of Special Relativity and that recognizing it is essential for a philosophical account of how laws are explained in this theory. As a case study, I consider the history of derivations of mass-energy equivalence which shows, I argue, that there are two distinct types of theoretical explanations in physics. One type is best characterized by the "top-down" account of scientific explanation, while the other is more accurately described by the "bottom-up" account. What is significant, I argue, is that the type of explanation a law receives depends on whether it is part of the framework theory or part of an interaction theory. The former only receive "top-down" explanations while the latter can also receive "bottom-up" explanations. Thus, I argue that current debates regarding "top-down" vs "bottom-up" views of scientific explanation can be clarified by recognizing the distinction between two levels of physical theory