which is associated with the organic synthesis which that energy serves to maintain. Verworn’s statement, it must be borne in mind, is as true of the composition of the Iliad as it is of the digestive process of an animalcule. The explanations above suggested are purely tentative; but so, it must be remembered, are the theories which they combat. No one pretends that the mechanical explanation of the universe, including the phenomena of organic life, is at present made out so as to cover the known facts, or even that expert opinion is at all unanimous in the belief that it can ever do so. I know no single work in which the present position of the controversy is so well set forth as in Professor V. L. Kellogg’s Darwinism To-day.[118] A great array of scientific authorities will there be found mustered, and the verdict of Professor Kellogg (reluctantly given, for he clings to the mechanical explanation of the universe) is that evolution is not explained by any mechanical force at present known to science. “With Osborn,” he concludes, “let us join the believers in the unknown factors in evolution.”[119] He does not, however, contemplate their remaining unknown—we have to say _Ignoramus_, not _Ignorabimus_; and by ‘known’ he means apparently, reducible to a mechanical process. He will have nothing to say to any internal force directing the energies of matter, such as the _Vervollkomnungsbewegung_ of Nägeli.[120] “Such an assumption,” he writes, “of a mystic, essentially teleologic force, wholly independent of and dominating all the physico-chemical forces and influences that we do know, and the reactions and behaviour of living matter to their influences which we are beginning to recognize and understand with some clearness and fulness—such a surrender of all our hardly won actual scientific knowledge in favour of an unknown, unproved, mystic, vital force we are not prepared to make.”[121] The above passage is very well fitted to be the pivot of the whole controversy. We shall examine it therefore in some detail. It is, in the first place, hardly correct to say that the _X_ factor in life and evolution is supposed by thinkers like Driesch, Reinke, and Nägeli to be ‘wholly independent of’ and to ‘dominate’ all the physico-chemical forces that we do scientifically know. Man, for example, cannot be said to be ‘wholly independent’ of the physico-chemical energies of which he makes use for a multitude of objects. He is very dependent, both on those outside him and those in his own organism. He cannot _originate_ the smallest quantum of physical energy. Yet he is unquestionably capable of directive action upon matter.