  It is of some philosophical interest that the relationship of thermodynamics to statistical mechanics shows some similarity to aspects uncovered in functionalist theories of the mind-body relationship. Consider, for example, the fact that systems of very different physical constitutions (say a gas made up of molecules interacting by means of forces on the one hand and on the other hand radiation whose components are energetically coupled wave lengths of light) can share thermodynamic features. They can, for example, be at the same temperature. Physically this means that the two systems, if initially in equilibrium and then energetically coupled, will retain their original equilibrium conditions. The parallel with the claim that a functionally defined mental state (a belief, say) can be instantiated in a wide variety of physical devices is clear.