6 THE EVOLUTION THEORY 



I nuist irpoat that I do not niran to say that everythmg is clear 

 ill rv'^iuA to thf cvohitioii of the living world. On the contrary, 

 1 bcliovr that we still stand merely on the threshold of investigation, 

 and tliat our insight into the mighty process of evolution, which has 

 Itrought ahont tlie endless diversity of life upon our earth, is still 

 very incomplete in relation to Avhat may yet he found out, and that, 

 instead of heing vainglorious, our attitude should he one of modesty. 

 We may well rejoice over the great step forward which the dominant 

 recognition of the Evolution theory implies, but we must confess that 

 the beirinninirs of life are as little clear to us as those of the solar 

 system. But we can do this at least : we can refer the innumerable 

 and wonderful inter-relations of the organic cosmos to their causes — 

 common descent and adaptation — and we can try to discover the ways 

 and means which have co-operated to bring the organic world to 

 the state in which we know it. 



When I say that the theory of descent is the most progressive 

 step that has yet been taken in the development of human know- 

 ledge, I am bound to give my reasons for this opinion. It is justified, 

 it seems to me, even by this fact alone, that the Evolution idea is not 

 merely a new light on the special region of biological science, zoology 

 and botany, but is of quite general importance. The conception of 

 an evolution of the world of life upon the earth reaches far bej^ond 

 the bounds of any single science, and influences our whole realm of 

 thought. It means nothing less than the elimination of the miracu- 

 lous from our knowledge of nature, and the placing of the phenomena 

 of life on the same plane as the other natural processes, that is, as 

 having been brought about by the same forces, and being subject 

 to the same laws. In the domain of the inorganic, no one now 

 doubts that out of nothing nothing can come ; energy and matter 

 are from everlasting to everlasting, they can neither be increased or 

 decreased, they can only be transformed — heat into mechanical 

 energy, into light, into electricity, and so on. For us moderns, the 

 lightning is no longer hurled by the Thunderer Zeus on the head 

 of the wicked, but, careless alike of merit or guilt, it strikes where 

 the electric tension finds the easiest and shortest line of discharge. 

 Thus to our mode of thought it now seems clear that no event in the 

 world of the living depends upon caprice, that at no time have organisms 

 been called forth out of nothing by the mighty word of a Creator, 

 but they have been produced at all times by the co-operation of the 

 existing forces of nature, and every species must have arisen just 

 where, and when, and in the form in which it actually did arise, as 

 the necessary outcome of the existing conditions of energy and 



