In this paper, I try to refute the Kantian a priorism. At the same time, I try to explain the existence of an a priori concerning space and time on the basis of contemporary neuro-physiology. This a priori is the opposite of the a-historical a priori of Kant. Concerning space and time, I argue that relativity concords with the philosophical thesis that space and time are forms of existence of matter. On the basis of this ontological principle, I support that (...) by accepting the existence of local absolute systems of reference, it is possible to explain some paradoxes of special relativity and at the same time to refute the relativism related to the theory of Einstein. (shrink)