Explanatory (A)symmetries and Humean Laws

Recently, Lange (2009) has argued that some physical principles are explanatorily prior to others. Lange’s main examples are symmetry principles, which he argues explain both conservation laws—through Noether’s Theorem—and features of dynamic laws—for example, the Lorentz invariance of QFT. Lange calls these “meta-laws” claims that his account of laws, which is built around the counterfactual stability of groups of statements, can capture the fact that these govern or constrain first-order laws, whereas other views, principally Humean views, can’t. After reviewing the problem Lange presents, I’ll show how the explanatory asymmetry between laws he describes follows naturally on a Humean understanding of what laws are—particularly informative summaries. The Humean should agree with Lange that symmetry principles are explanatorily prior to both conservation laws and dynamic theories like QFT; however, I’ll argue that Lange is wrong to consider these principles “meta-laws” which in some way govern first-order laws, and I’ll show that on the Humean view, the explanation of these two sorts of laws from symmetry principles is importantly different.