THE SPECTRE OF VITALISM 449 



can trace the stimulus from the outer air to the auditory nerve : 

 but the infinite complexity which characterises the various 

 nuclei and nervous bodies to which it proceeds they cannot yet 

 trace. How then can we allow Driesch to make the a priori 

 assertion that no mechanism could account for the variations 

 in reactions to similar stimuli ? We have traced the stimulus 

 with a variety of changes of form through the auditory 

 machine. We lose sight of its path only at the point where the 

 machine becomes so excessively complex, the paths of conduction 

 so infinite in number, that its progress can be traced no further. 

 And yet because the ultimate reaction is liable to extreme 

 variation with respect to the stimulus, we are asked to believe 

 that a mechanical procedure is impossible! 



We may not know how a watch works : but we do not there- 

 upon deny that it is a machine (though savages do, by the way : 

 they think it is alive and the vitalists among them would no 

 doubt explain its action as due to a " horologic force "). I contend 

 that Driesch has not produced an atom of evidence in support of 

 his opinion that physical mechanism is inadequate to account for 

 the different mental associations set up by mechanically similar 

 stimuli. The original external stimulus in the form of molecular 

 vibrations of the air is transformed by the auditory machine into 

 vibrations of smaller amplitude and greater intensity, in order to 

 be transformable again into nerve currents. Driesch might well 

 say that such a transformation was inexplicable on mechanical 

 principles, had not the actual mechanism been discovered. But 

 if this machine be complex, its complexity is as nothing in com- 

 parison with that of the brain where the effects of the stimulus 

 operate. In short, the appearances are so strongly in favour of 

 a mechanical action, that it would be difficult to imagine any 

 other hypothesis. 



It becomes possible to account in part for Driesch's difficulty 

 in believing in a mechanical action, if we note that he already 

 begs the whole question by a false definition of a machine. He 

 says : " Does it not contradict the very concept of a ' machine,' 

 i.e. a typical arrangement of parts built up for special purposes^ to 

 suppose that it originates by contingencies from without ? " His 

 argument, as I understand it, is that cerebral reactions to stimuli 

 are regulated largely by the previous stimuli or " experience" of 

 the brain and that, since this is a matter of chance and since 

 machines are things of definite purpose, cerebral action cannot 



