Systems thinker Neil Wilson gives a very clear exposition of how the exogenous (vertical) and endogenous (horizontal) system interact, with the central bank and its currency powers at the apex of the hierarchy that includes the Treasury and banks as public-private partnerships. This system is at the core of modern economies, all of which use state money as central bank created currency in addition to credit money created by bank loans that presupposes use of currency for final settlement.
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The fixed exchange rate system at the heart of MMT
by Neil Wilson