 The ordinary Second Law of thermodynamics is, at bottom, an empirical generalization based on observation of the behavior of ordinary material systems, albeit one with confirmation and thus entrenchment more profound than probably any other single principle in all of physics. One of the most remarkable features of the Generalized Second Law, by contrast, is that it seems to admit of proof in ways much more mathematically rigorous than does the ordinary Second Law (such as, e.g., the proof of Flanagan et al. 2000, in the context of classical general relativity and theories of matter, and a number of proofs in different contexts given in and discussed by Wall 2009). That already raises interesting philosophical questions about the relations between what seems prima facie to be the “same” fundamental principle as formulated, evaluated and interpreted in different physical theories. 