A priori, a posteriori or Heidegger contra Kant

Recently I have become interested in the problem of epistemology and Kant's Critique of pure reason seemed like a good starting point. Kant makes quite a convincing point about a priori categories, namely time and space. He claims that these categories are preconditions for any sensory and cognitive activity. Categories should be distinguished from ideas and concepts: that the subject necessarily has an a priori category of time does not mean that it has a positive idea of time (the fact that the idea of time is culturally specific - linear and circular time being two most common examples - would obviously disprove that) but that there necessarily exists a category which allows phenomena to exist in the relationship of before and after. If this were not an a priori category no meaningful interaction would be possible, because we would not be able to conceptualize things like action/reaction, cause/effect, even a notion of self - which is at its core a notion of temporal continuity - would be quite impossible. After proving this point Kant is content to leave the matter as it stands and does not investigate into the origins of these a priori categories. He was wise enough to know that in the context of his philosophical system this endeavour would have been futile. The problem is that it is framed as an epistemological, not ontological, problem. In the context of idealism with its fixation on the primacy of the subject all ontology boils down to epistemology in the end, that is why the answer necessarily eluded Kant.

Fast forward then to Heidegger, a man who could have been a great philosopher, were his tremendous sagacity not coupled with an even greater measure of senselessness. To put it more precisely: a man, who refused to take the obvious step all the inconsistencies and paradoxes of his system called for - the step from metaphysics to materialism - only for the sake of acting as a mouthpiece of the Third Reich, even as the Reich had been long dead. I will be so bold to take this step, the step his servile cowardice prevented him to take, for him. For Heidegger in Being and time then the starting point was not epistemology, he took a broader perspective and claimed that being-in-the-world is antecedent and is a precondition for knowing the world. This allows us to solve the riddle of the origin of a priori categories: they are ontological characteristics of the subject's being-in-the-world, time and space are something that the subject shares with the object, and only by virtue of this commonality can the subject know anything about the world. For Kant a priori categories were something at home in the subject, they were something the subject imposed on the world, no wonder then that the object - the infamous Ding an sich - eluded him. The truth is that a priori categories are not merely subjective and it is this fact which makes cognition possible in the first place. The problem with Heidegger is that upon discovering this fact he ran amok and tried to subsume everything to the realm of Dasein. While there can be no doubt that time and space as physical categories are things society and individuals can have little influence on, Heidegger envisions the whole of society to this be similarly beyond reproach and adds history to boot. His philosophy becomes a giant apology for the status quo, the most ferocious one since Hegel, indeed ferocious enough that Heidegger's epitaph might have read: "No, you must not think everything is true, merely that it is necessary."