LTT: R. Batterman

I argue that this reductionist approach is not fruitful and cannot explain the relative autonomy/universality of the continuum theories—theories that continue to be used in engineering contexts. Instead, I describe an approach that appeals to order parameters and material parameters understood to be defined at mesoscales. That is, we need to treat order parameters and material parameters as natural kinds that live at mesoscales in between the continuum and the atomic scales.  This approach is natural from the perspective of condensed matter physics and materials science.  It is not new and has its origins in (quantum) field theoretic approaches to many-body systems developed by Schwinger, Martin, and Kadanoff, among others.  It reflects a widespread methodology that has almost completely been ignored by philosophers of science. A key aspect of arguing for the naturalness of such mesoscale parameters is provided by the Fluctuation-Dissipation theorem of statistical mechanics.