D. Some psychological issues

Cosmology presents physics with a formidable challenge. The Universe is not a bounded and isolated system. The Universe is far from being in any form of dynamical equilibrium. The gravitational force is of infinite range and always attractive. Nor can we experiment on the subject of interest, we are mere observers. Thus the usual concepts from statistical physics cannot be simply imported, they have to be redefined to suit these special circumstances.

This process of redefinition is apt to misdirect the struggle for understanding the issues involved and is inevitably frustrating to those who work in statistical physics or who seek to use techniques from statistical physics. Indeed there have been occasions where the notions of the standard model have been abandoned simply in order to exploit standard concepts that would otherwise be invalid (eg.: model universes having one spatial dimension or model universes that have zero mean density in the large). Those papers may be interesting, but they have little or nothing to do with the Universe as we know it.