This concluding chapter focuses on the philosophical lessons to be had from the discussions in the previous chapters. Specifically, it suggests that one interesting and fruitful way to understand the relation “theory X is more fundamental than theory Y” is through mediated mesoscale modeling. This is in contrast to the kind of direction derivational connections often invoked in the debates about reduction that depend on “in principle” mathematical claims. The hierarchical ordering in terms of this relation of relative fundamentality can be understood in terms of the conception of relative autonomy discussed throughout the book. It highlights the fact that this point of view has its genesis in Einstein’s work on Brownian Motion and specifically in his determination of an effective material parameter and the first expression of the Fluctuation-Dissipation theorem. Finally, it recaps the conception of an engineering, middle-out approach to many-body physics and the physical arguments that certain mesoscale variables should be considered to be natural kinds.
On the transient fluctuation dissipation theorem after a quench at a critical point
