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pragmatist comments on In Praise of Boredom - Less Wrong

23 Post author: Eliezer_Yudkowsky 18 January 2009 09:03AM

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Comment author: pragmatist 15 June 2012 02:15:37AM *  4 points [-]

Extremum rate principles like MEP have proven very useful for describing the behavior of certain systems, but the extrapolation of the principle into a general law of nature remains hugely speculative. In fact, at this point I think the status of MEP can be described as "not even wrong", because we do not yet have a a rigorous notion of thermodynamic entropy that extends unproblematically to nonequilibrium states. The literature on entropy production usually relies on equations for the entropy production rate that are compatible with our usual definition of thermodynamic entropy when we are dealing with quasistatic transformations, but if we use these rate equations as the basis for deriving a non-equilibrium conception of entropy we get absurd results (like ascribing infinite entropy to non-equilibrium states).

Dewar's work, which you link below, is an improvement, in that it operates with a notion of entropy that is clearly defined both in and out of equilibrium, derived from the MaxEnt formalism. But the relationship of this entropy to thermodynamic entropy when we're out of equilibrium is not obvious. Also, Dewar's derivation of MEP relies on applying some very specific and nonstandard constraints to the problem, constraints whose general applicability he does not really justify. If I were permitted to jury-rig the constraints, I could derive all kinds of principles using MaxEnt. But of course, that wouldn't be enough to establish those principles as natural law.

Comment author: timtyler 15 June 2012 10:02:53AM *  0 points [-]

Extremum rate principles like MEP have proven very useful for describing the behavior of certain systems, but the extrapolation of the principle into a general law of nature remains hugely speculative. In fact, at this point I think the status of MEP can be described as "not even wrong", because we do not yet have a a rigorous notion of thermodynamic entropy that extends unproblematically to nonequilibrium states.

Entropy and MEP are statistical phenomena. Thermodynamics is an application This has been understood since Boltzmann's era. Most of the associated "controversy" just looks like ignorance to me.

Entropy maximisation in living systems has been around since Lotka 1922. Universal Darwinism applies it to all CAS. Lots of people don't understand it - but that isn't really much of an argument.