Given physical systems, counting rule for their statistical mechanical
descriptions need not be unique, in general. It is shown that this
nonuniqueness leads to the existence of various canonical ensemble theories
which equally arise from the definite microcanonical basis. Thus, the Gibbs
theorem for canonical ensemble theory is not universal, and the maximum entropy
principle is to be appropriately modefied for each physical context.Comment: 13 pages; This is a thoroughly revised version of the original
preprint which has now appearted in print. It also corrects several errors
and misstatements in the published version. The main conclusions of the paper
however remain intac