“With the exception of energy, all the other concepts whose importance comes second to that of the law of the conservation of energy, find their application only within a limited field of natural phenomena. Energy alone finds itself again, without exception, in all natural phenomena; that is to say, all natural phenomena permit of being ranged under the concept of energy.” Further on he says: “All that we know of the external world we can represent in the form of propositions concerning actually-existing energies; hence the concept of energy proves itself in every way the most universal that science has yet framed. It comprehends not only the problem of substance, but also that of causality.” Taken literally, word for word, all this is quite correct, and yet as a whole is founded in a total misunderstanding of actuality. That all natural phenomena should admit of being ranged under the concept of energy, _i.e._ of _work done_, is due solely to the fact that _everywhere actual energies_ are in activity; of these energies, however, we know nothing, absolutely nothing; and their universal presence is proven solely by the universal presence of work. And that work is only the reaction of actual energies is made evident by the fact that the one single _actual_ energy we can get at--consciousness--is the one single value in the universe which never under any circumstances admits of being “read” as work. When further on in the same volume it is said:-- “As regards the inverse endeavour to comprehend energies apart from matter, for long one dared not attempt such a thing, albeit it was soon perceived that as a matter of fact all we ever learn about the world consists solely of a knowledge of its energical relations.... We will, therefore, venture the attempt to build up a view of the world from which the concept of matter will be absent, a view composed exclusively of energical materials (_i.e._ of the fact _work_),” this has about as much meaning as if some one should say, “I will endeavour, out of shadows and their innumerable modifications alone, to furnish a complete theory of light.” Here we have to do simply with the occurrence designated in another place as the “inversion of positions.” From an extreme materialistic position one leaps at a bound into an equally extreme energical position--each position as purely dialectical as the other. If only one held by _actuality_, one would of oneself repudiate as a profitless mental diversion the very _attempt_ to erect a world-theory upon such premisses. On such one may build up physical systems, achieve technical successes, measure, compute in advance--in fine, carry on scientific studies; but one thing one can never do--out of them build up a view of the world. For a view of the world in which consciousness excludes itself from that which is to be comprehended, has precisely as much value as a numerator without a denominator.