Every area of research has two boundaries marking the point at which the process of reflection ceases to be exact and takes on a philosophical character. The pre-conditions for cognition in general, like the axioms of every specific domain, cannot be presented and tested within the latter domain, but rather they call for a science of a more fundamental nature. The goal of this science, which is located in infinity, is to think without preconditions-a goal which the individual sciences deny themselves since they do not take any step without proof, that is, without pre-conditions of a substantive and methodological nature. Philosophy, too, cannot completely transcend such pre-conditions with regard to its own activity when it presents and tests them. But in this case, it is always the last point of cognition at which an authoritative decision and the appeal to the unprovable arises within us, and yet in view of the advances made in terms of what can be proved this point is never definitively fixed. If the start of the philosophical domain marks, as it were, the lower boundary of the exact domain, then its upper boundary lies at the point where the everfragmentary contents of positive knowledge seek to be augmented by definitive concepts into a world picture and to be related to the totality of life. If the history of the sciences really does reveal that the philosophical mode of cognition is the primitive mode, is a mere estimate of the phenomena in general concepts, then this provisional procedure is nevertheless indispensable when confronted with certain questions, namely those questions-especially those related to valuations and the most general relations of intellectual life-that we have so far been unable either to answer or to dismiss. Moreover, even the empirical in its perfected state might no more replace philosophy as an interpretation, a colouring and an individually selective emphasis of what is real than would the perfection of the mechanical reproduction of phenomena make the visual arts superfluous.