If rational science becomes a problem, if the claim of the purely a priori sciences to have unconditional objective validity, and thus to be the possible and necessary method for rational sciences of fact, becomes a problem, it should first be taken into consideration (as we emphasized above) that science in general is a human accomplishment, an accomplishment of human beings who find themselves in the world, the world of general experience, and that it is one among other types of practical accomplishments which is aimed at spiritual structures of a certain sort called theoretical.