... "the tripod is the most stable form of government" is Kant. My sense is that most of the chapter epigraphs in Herbert's Dune books are fliched from Nietzsche, Hegel, Kant etc. (Kant's tripod was specifically what he called "perpetual peace": [a] "republican constitutions" (we would say: representative democracy); [b] a "commercial spirit" of trade and economic interdependence and [c] international law. Different to Herbert's three things)