I believe I've discussed this before in this blog but, hey, I'm old enough so that you have to expect that I've repeated myself now and then. According to one theory -- one with a certain level of plausibility to it at least -- the societies of the world fall into three classes as defined by water: the dry, the temperate, and the wet. With the dry, large-scale irrigation is essential to any agriculture at all. With the wet, dikes and flood control measures are an imperative. In temperate parts of the world, neither of those needs is quite so urgent, and they can be handled at smaller, localized, scales. Projects that require great scale require great states, powerful imperial centers. On this logic, small states, and individual liberty, has only been possible in the lucky goldilocks parts of the world, neither wet enough nor dry enough to create those unquestionable imperial centers.