Plato's political theory is about the "constitutions" of societies. But a constitution (politeia in Greek) is how something is organized, and he also notices that there are parallels between how societies and souls are constituted. For example, societies organized around status (as if status were the best thing in life) tend to be populated by people who love status above all. So too for money. Education is the link. Societies reproduce themselves by educating people in their image.  

Recommended Readings: Plato, Republic 8, 543a1 - 555b1

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