Burbury's Last Case: The Mystery of the Entropic Arrow

this paper, but take it to be merely a placeholder for more specific descriptions of the relevant properties of time-asymmetric thermodynamic systems. 3. Two Models of the Origin of the Thermodynamic Asymmetry In this section I distinguish two different explanatory models for the thermodynamic asymmetry. In my view, insufficient attention to this distinction does a great deal to explain the striking lack of consensus about this topic---in particular, it explains the major respect in which various participants in the debate have been talking at cross purposes. 3.1 The two-asymmetry view As noted above, the nineteenth century attempt to reduce thermodynamics to statistical mechanics led to two realisations about the Second Law: first, that it is probabilistic rather than strictly universal in nature; and second, that it is time-asymmetric. As a result, the Second Law is commonly seen as a time-asymmetric probabilistic generalisation, with a lawlike or quasi-lawlike character---a general constraint on the behaviour of matter, preventing or at least discouraging (in a probabilistic sense) entropy from decreasing, in the ordinary time sense. What does `lawlike' mean in this context? This question deserves more attention than I can give it here, but for present purposes the crucial feature seems to be projectibility. At the very least, for two-asymmetry views, the Second Law retains the status of a time-asymmetric generalisation on which we are entitled to rely, in forming expectations about the future behaviour of matter. (As we shall see, it cannot have this status for one-asymmetry views.) The nomological character of two-asymmetry approaches sometimes also shows up as the view that matter has a certain time-asymmetric property, or disposition---that of being `thermodyn..