He rightly reproaches rationalism for neglecting questions which should have been its fundamental questions; that is, it had never penetrated to the subjective structure of our world consciousness prior to and within scientific knowledge and thus had never asked how the world, which appears straightforwardly to us men, and to us as scientists, comes to be knowable a priori how, that is, the exact science of nature is possible, the science for which, after all, pure mathematics, together with a further pure a priori, is the instrument of all knowledge which is objective, .e., unconditionally valid for everyone who is rational (who thinks logically).