30 THE LIVING WORLD. 



vital force, for of course we can get .no conception 

 of any force except by its results. But the vitalistic 

 theory claims that life is an immaterial something 

 which directs physical processes so as to produce the 

 activities which distinguish living things. We need 

 not further consider this view, for it consists chiefly 

 in recognizing the necessity of something more than 

 chemical affinity and change, and in acknowledging 

 our inability to explain it by giving to it the name 

 vitality. 



The Mechanical Theory of Life. 



The point of dispute to-day is not whether the 

 vitalistic theory would explain facts, but whether it 

 is necessary. A purely mechanical view of life has 

 slowly arisen from the profuse speculations, which 

 claims to be able to meet the case without recourse 

 to any imaginary " vital force." The general ten- 

 dency of scientific thought gives a certain amount 

 of a priori bias in favor of such a view. It has 

 unquestionably been the tendency of science to 

 explain more and more of the phenomena of the 

 world in terms of the properties and laws of the 

 natural universe. The foundation of the law of the 

 conservation of energy, the conception of forces as 

 modes of motions, are great steps in this direction. 

 In the organic world the theory of evolution, the 

 application of the conservation of energy to the 

 mechanics of life, the perception that the same 

 chemical laws govern living things and dead, and 

 every discovery of likeness between vital processes 

 and those purely mechanical, are all steps toward 



