Brute Facts, Social Facts, and Institutional Facts

Geographic regions (henceforth, regions for short) are spatially extended pieces of (near) earth surface that share some aspect of similarity across their extents. The most fundamental aspect of similarity shared within a region is "locational similarity"-proximity. But regions nearly always share common thematic content or activity too. That is, regions are defined not just spatially but according to the human and natural entities or processes occurring there. Regionalization is spatial categorization, and importantly, this spatiality is literal rather than metaphorical, as it is with most other category systems. The modifier "geographic" implies a region of space that is prototypically two-dimensional (though often bumpy or uneven) and at or near the earth surface. Volumetric exceptions exist underground and in the atmosphere, but they are rare given the geogra­ pher's interest in the earth as the home of human habitation. Also because of the human-centered focus of geography, the human and natural themes that provide content for regions are usually phenomena at human-centered spatial and temporal scales-not too fast or small, not too slow or large (Montello 2001). The fact that geographic regions typically encompass places that are close together is interesting and conceptually nontrivial because it leads to a generalization about the shape of regions. Regions tend to be