I not consider GJ Mattey’s quote of Kant’s critique as sufficent in terms of the intellectualization of matter, as You describe, because he has taken the Noumina as am equivalent non-material, albeit divorced materially. What Kant is doing,is trying to preserve, e.g. synthesize the two, bringing in Hume’s absolute material interpretation, yet trying to save the noumenal, immaterial part. Mathematically, the idea of synthesis does not work on any level, the idea of a pure understanding works on the levelmof approximation. Hegel took the ideological dielectic as the form of pure understanding, his synthesis not abject to the one Kant was up against, in the question posed, 'How are synthetic a-priori judgements possible?
That history did in fact not bear him up on this, is proof positive of the dubious nature of his ontology in this regard.
I Leibnitz’s case, the mathematical model of understanding is successfully demonstrated, as applied to pure logicsl diagrams of functional relation. That this can be adapted toward the models upon which theories of sets, limits, and approximations are based, I i to the idea of the functional use, of models correlated and not synthesized with them.
Monadology resembles atomism, which in fact has turned out to be the right intellectual model to a theory of the material universe. The question arises as to the nature of mathematical models, and that is a different question.
But to ascribe a synthesis , is only an effort to unify an intrinsic theory of pattern recognition and logical criteria and try to unify it with it’s material counterpaert , as it was a material idea. This has proven to be a failure for Marx, a disaster of what i consider more of ascribing political revision in detriment of ontological certainty.
Ethics, as has been pointed out, was not an original concept, but brought back from classical sources, and dressed up in an a-posteriori proof, as it were.
I agree, that Kant embodied a stage in philosophy,
which could not be circumsribed, because the fallacy of the a-priori synthetic was needed to demonstrate the more relevant dialectic of the pure understanding, which in turn had to be surpassed by it’s nihilization, and it’s ultimate existentially based reduction, an anti development of the progressive decay of Hegel. Inn any case, Leibnitz pre dated this problem by his model.