Here this is quite enough to signalize the nature of the law of the conservation of energy. In the conception of the play of world-events as yielded by this law, the physicist turns his eyes entirely away from the real, active energies of the play of world-events. He confines himself entirely to what is exhibited to sense, the motions; he takes them for the forces themselves, but is entitled to do so only so long as he keeps clear before him the fact that it is only a _reading_ that is in question, and derives therefrom what alone can be derived--_work done_. Work done, however, is not energy itself but the reaction from energies. And that which the physicist calls the “world-picture of energetics” is, in point of fact, void of all energies. The entire world-picture of energetics is no _actual_ thing but, in the strictest sense, a thing _re-actual_,--if such a word may be coined--which as such has no title whatever to be used as a world-theory. Should, nevertheless, this occur, then those consequences follow about which we shall speak later. So long as science abides by actuality she can say nothing else but that every attempt to trace back completely one phenomenon of life to another--that is, to represent the play of world-events in the form of pure relation-values--slips into an endless series; and what is most of all worthy of remark, each member of this endless series is itself in turn the point of departure for a new endless series, so that in the last analysis the fact of this limitless comprehensibility of the phenomena of life remains as the one real problem of science. And every science that is in earnest, and does not merely seek to avail itself of technique, at the very outset must ask itself the question, This limitless onward movement which every point of departure yields, start where we may, has it or has it not a conclusion? To be able to judge of that one must possess some firm standing-ground from which to look out and see whether this unceasing progression really is progress. On this journey upon the high seas of knowledge one must have a landmark by which to steer. Such a possibility, however, is excluded, and excluded by science itself. For, as already said, science as such has standing only where the hypothesis of potential comprehensibility, of the absence of all that is not perceptible to sense holds good; in other words, where the play of world-events admits of being resolved without remainder into relation-values. Such a landmark, however, could only be something which itself did not admit of being resolved into pure relation-values, but was a constant in itself, an unconditioned constant. Were science, however, to admit the existence of such a “something,” she would be cutting the ground from under her own feet. The whole value of science, as such, resides in its pure relativity, in the liability of its values; even as the value of faith resides in the fixity of its one value.