Biological evolution is generally regarded as a stochastic or probabilistic process, per the ideas of Darwin in the nineteenth century. Even if this is true at the meso-scale, it still may, however, be impacted by overarching constraints that we have not yet identified. In this paper, we revisit the subject of mammal faunal regions with a mind to explore a potential kind of macroevolutionary influence. We first identify an optimum seven-region mammal faunal classification system based on spatial and phylogenetic data from a comprehensive 2013 review, and then examine the possibility that this classification provides supporting evidence for a Spinoza-influenced philosophical/theoretical model of the "natural system" concept developed by one of the authors in the 1980s. The hierarchical pattern of regional affinities revealed does do this.
Keywords: Spinoza; classification; evolution; faunal regions; mammals; natural systems.