On the rubble of European spirituality and medieval mysticism, with their completely natural will to self-assertion, these spiritual low-flyers built their tower-like empires on the narrowest steps and footbridges over dizzying abysses. At least historically, their often too entwined paths of thought lead to fainting.
Such "thinking" is in fact based on a "naive" conception of truth and being, which cannot be "fixed" by any "epistemology" or whatever. You cannot prove anything really true. That you have to prove something at all shows just how weak you really are.