Thus, for mankind aware, there is a double problem, that of Waking-Being and that of Being; or of Space and of Time; or of the world-as-nature[13] and the world as history; or of pulse and tension. The waking consciousness seeks to understand not only itself, but in addition something that is akin to itself. Though an inner voice may tell one that here all possibilities of knowledge are left behind, yet, in spite of it, fear overpersuades--everyone--and one goes on with the search, preferring even the pretence of a solution to the alternative of looking into nothingness. IV Waking-consciousness consists of sensation and understanding, and their common essence is a continuous self-adjustment in relation to the macrocosm. To that extent waking-consciousness is identical with ascertainment (_Feststellen_), whether we consider the touch of an infusorian, or human thinking of the highest order. Feeling, now, for touch with itself in this wise, the waking-consciousness first encounters the epistemological problem. What do we mean by cognition, or by the knowledge of cognition? And what is the relation between the original meanings of these terms and their later formulations in words? Waking and sleep alternate, like day and night, according to the course of the stars, and so, too, cognition alternates with dreams. How do these two differ? Waking-consciousness, however--whether it be that of sensation or that of understanding--is synonymous with the existence of oppositions, such as that between cognition and the object cognized, or thing and property, or object and event. Wherein consists the essence of these oppositions? And so arises the second problem, that of _causality_. When we give the names “cause” and “effect” to a pair of sensuous elements, or “premiss” and “consequence” to a pair of intellectual elements, we are fixing between them a relation of power and rank--when one is there, the other must be there also. In these relations, observe, time does not figure at all. We are concerned not with facts of destiny, but with causal truths, not with a “When?” but with a law-fixed dependence. Beyond doubt this is the understanding’s most promising line of activity. Mankind perhaps owes to discoveries of this order his happiest moments; and thus he proceeds, from these oppositions in the near and present things of everyday life that strike him immediately, forward in an endless series of conclusions to the first and final causes in the structure of nature that he calls God and the meaning of the world. He assembles, orders, and reviews his system, his dogma of law-governed connexions, and he finds in it a refuge from the unforeseen. He who can demonstrate, fears no longer. But wherein consists the essence of causality? Does it lie in knowing, in the known, or in a unity of both?