"Thermodynamics is an incredibly fundamental theory...," says Milburn..."
Yes it is. Something that is not defined always increases so that we have a law of Nature, thanks to "the unargued statements of Kelvin, the bold claims of Clausius and the strained attempts of Planck". This law represents "an obstacle to the reconciliation of different theories of physics" and the discussion of it is "a red herring". Nevertheless, or because of that, the law holds "the supreme position among the laws of Nature" - any theory found to be against it collapses "in deepest humiliation":
http://www.bourbaphy.fr/price.pdf
Huw Price, Time's Arrow and Eddington's Challenge, p. 122: "A lot of time and ink has been devoted to the question how entropy should be defined, or whether it can be defined at all in certain cases (e.g., for the universe as a whole). It would be easy to get the impression that the puzzle of the thermodynamic asymmetry depends on all this discussion - that whether there's really a puzzle depends on how, and whether, entropy can be defined, perhaps."
http://philsci-archive.pitt.edu/archive/00000313/
Jos Uffink, Bluff your Way in the Second Law of Thermodynamics, p. 94: "This summary leads to the question whether it is fruitful to see irreversibility or time-asymmetry as the essence of the second law. Is it not more straightforward, in view of the unargued statements of Kelvin, the bold claims of Clausius and the strained attempts of Planck, to give up this idea? I believe that Ehrenfest-Afanassjewa was right in her verdict that the discussion about the arrow of time as expressed in the second law of the thermodynamics is actually a RED HERRING. The only way to evaluate such a proposal is by making up a balance-sheet. What would we loose and what would we gain? It is clear that in fact all concrete applications of the second law in classical thermodynamics, even in the work of the most outspoken proponents of the claim that this law implies universal irreversibility, are restricted to systems in equilibrium. This holds for Kelvin and Planck, but also more recent text books (e.g. (Becker 1967)). A general opinion among thermodynamicists is even that the theory is incapable of dealing with systems out of equilibrium; (see the quotation from Bridgman on page 3). Clearly, in terms of concrete applications, we would loose very little. What, then, do we gain with this proposal? The main advantage is, to my mind, that the second law would no longer represent an obstacle to the reconciliation of different theories of physics."
http://web.mit.edu/keenansymposium/overview/background/index.html
Arthur Eddington: "The law that entropy always increases, holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations - then so much the worse for Maxwell's equations. If it is found to be contradicted by observation - well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics, I can give you no hope; there is nothing for it but to collapse in deepest humiliation."
Pentcho Valev pvalev@yahoo.com