UC San Diego

Physicists have historically taken the concepts of classical thermodynamics to be universally applicable, well-understood, and secure. Thus Eddington’s famous proclamation that “the law that entropy always increases, holds, I think, the supreme position among the laws of Nature”, and that “if your theory is found to be against the second law of thermodynamics, Ican give you no hope; there is nothing for it but to collapse in deepest humiliation.” (1928, 74) Somewhat more cautiously, Einstein remarked that “[classical thermodynamics] is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of applicability of its basic concepts.” (1946, 33) Suffice to say, classical thermodynamics is accorded a special status few other physical theories could dream of having. This can still be observed in contemporary physics, where classical thermodynamic concepts are typically borrowed wholesale and applied into new domains like black hole physics and quantum gravity research by physicists like Bekenstein, Hawking, and others.

My task here is to subject this faith in classical thermodynamics to philosophical scrutiny. What is the ‘framework of applicability’ for thermodynamic concepts, and what are its limits? In this vein, my dissertation critically examines and challenges the foundations of thermodynamics by studying the historical trajectory of classical thermodynamic concepts and their justifications, as well as the extent to which these justifications can be carried over to new domains of inquiry. In particular, I survey how classical thermodynamic concepts extend into the domains of information theory, quantum mechanics, special relativity, general relativity, and quantum gravity. I argue that the ‘framework of applicability’ of classical thermodynamic concepts is more limited than typically assumed, and more open questions remain in the foundations of thermodynamics than one might expect.