An interesting demonstration of this approach's high level of generality, is its ability to evaluate the central tenet of Keynes' "General Theory …" what he calls a "psychological law", or the propensity of individuals in a community to proportionally save more than consume out of any marginal increase in income; to be compensated for, by increasing entrepreneurial investment in order to maintain full employment. Sidestepping for a moment, how far away from ourselves we can push the philosophical need for exogeneity to impart sense a priori, there is no apparent conflict; if the population is axiomatically taken to be endogenous, its quantified activities are determinate by definition. But his recognition that consumption is the sole end and object of all economic activity, with unemployment being [a] necessary [evil?] to keep investment at a level not to exceed the provision of future consumptive demand, (the latter being hinted at on p.105 of the GT) depicts a systematic situation in dynamic equilibrium over time; with an exogenous population being purposefully served, just as in the proposed new paradigm.
So even though Keynes professes "to state the obvious", I don't think he fully grasped its deep-going ramifications. That first part of the assertion comprises a fair bit of data, and if we parse it further it means that consumption determines value, and anterior to consumption, all values are indeterminate. Because means-of-production investment occurs prior to consumption; in Keynes' model this is both indeterminate over time (as in the "obvious" first sentence), and determinate with an endogenous population
in time, as he takes it to be in the bulk of the GT and in particular regarding its MEC calculations. Hence the internal contradiction and resulting overdetermination of economic-asset valuations in his GT.
All exogenous impulses (propensities, animal spirits, investment decisions, CB interventions and the like) are indeterminate by definition and, needing an endogenous reaction, cannot produce determinate effects; they neither, by themselves, can be equilibrating, nor depended upon to restore an existing disequilibrium. In Keynes' overdetermined model they effect paradoxes, or a "riddle" as he calls it; which in and of itself is already proof of erroneous, and/or too many, premises or axioms. Endogenous population economic theories are most problematic, as objectivity has to fall by the wayside; and even if 'subjective quantification' is no utter self-contradiction in terms, its rationalization is tautological at best.
Meanwhile, the "novel expedient" he is looking for is not so novel at all; it finds its cradle with Adam Smith and the classical separate determinants (resolves) of wages, rents, and profits. Keynes' obligation to Marshallian ex ante scissor-blades' determination simply proved too great an obstacle, leading to an internally contradictory half-way measure of induced investment to tackle the unemployment problem; for not full employment but neutral money, through the time it takes to fully
resolve economic costs and profits, is the condition whereby the (neo)classical edification would come into its own again. The marginalists' approach to economics, apparently oblivious that exogeneity is imperative to prevent a degeneration into meaningless circular reasoning, while charting a make-belief course as if the economy is an ex ante determinate structure, can never comprise reality either; so it is a dead end for the very same reason. And any socio-economic order, although able to confer rights upon endogenous abstractions (capital, interest, income) as if these are real, is yet altogether powerless to prevent the occurrence of crises and/or burst economic bubbles, that arise from not having heeded to the very difference between abstraction and reality. The only option to get to the bottom of all of this, is to go back as far as Sismondi's first hints about determination, and endogenous economic values being abstract, and take it from there.