KP: I am a tad busy right now, so I don't think I will have time for a long point/counterpoint. However, I would like to point out that the argument you are attributing to me is not the one I was trying to make. I am not questioning the legitimacy of all a priori reasoning. I was pointing out that philosophers have often made armchair pronouncements about what must or must not be, which scientists have blithely disregarded and proceeded to do what philosophers said could not be done. Leibniz, for instance, claimed to disprove the possibility of physical atoms. Scientists went right ahead with atomic theory--and a good thing too. Kant held that three dimensional space was an a priori intuition. Physicists have found it useful to disregard that "intuition." Spinoza "proved" that all that is must be. Quantum physics does not give a fig for such determinism. Auguste Comte said that the constitution of the stars would never be known. A year or two later the spectrograph was invented. Kant held that asserting either that the universe had a beginning or did not leads to insoluble intellectual antinomies. Big Bang theorists never cared. Descartes "proved" that the mind must be incorporeal res cogitans. Neuroscience piles success on top of success assuming that we think with our brains.
VR: But of course, the argument here isn't just an armchair speculation, it is a principed argument. In these cases, it has to be clarified that the scientific theory and the philosophical argument really contradicted one another. I know in the case of Kant, it is an open question as to whether the claims are really in conflict. This is the discussion of it in the Stanford Encyclopedia.
It doesn't seem to me that Kant's position, just described, conflicts with scientific theory.