A SURVEY OF THE PROBLEM OF VITALISM 419 



and of every part of the organic world that has been brought 

 within the range of observation, what right have you to affirm 

 that the part still remaining outside the sphere of observation 

 is managed on a totally and unutterably different system from 

 anything that we have ever met with in nature ? Further, he 

 continues, supposing it to be true that physico-chemical forces 

 do not control the higher organic activities, what are your 

 grounds for alleging that they are controlled by a vital force, 

 or by any spiritual agency? When we invoke physical or 

 chemical forces, we are dealing in things we understand and 

 can investigate at leisure : we know what we are talking about. 

 But when you invoke a spiritual or vital force, you are dragging 

 in a new and unknown conception, of which you have not the 

 slightest knowledge, nor the slenderest rag of evidence for its 

 existence. If you succeeded in proving that physico-chemical 

 forces were not the active agency in mental processes, you 

 ought to be satisfied with that and say no more. But you go 

 farther : you are prepared to tell us what is the active agency : 

 you speak of a force which really is meaningless to us ; and 

 notwithstanding the considerable fortress of words with which 

 you strengthen your theory, that theory remains outside the 

 range of human intellect, and we are no wiser than we should 

 be if you confined yourself to denying the all-sufficiency of 

 mechanical forces. 



Let us, however, limit ourselves, as a few — very few — 

 vitalists have done, to this more modest proposition ; and let 

 us recognise its implications. Modern researches in the 

 physiology of the nervous system indicate that the reflex arc is 

 the functional unit of that system ; and indeed that the system 

 has been built up in the course of evolution by the multiplica- 

 tion of reflex arcs, and their superimposition upon one another 

 to a degree of almost infinite number and complexity. In the 

 simple, typical reflex arc (which, by the way, is an abstraction 

 nowhere found in nature, though none the less a useful con- 

 ception) a stimulus at one end of the arc is conveyed down an 

 afferent nerve to the central ganglion, whence proceeds a 

 further impulse along an efferent nerve to (say) a muscle, which 

 thereupon undergoes contraction. The contraction of the 

 muscle is dependent upon the original stimulus, and follows 

 necessarily and fatally upon that stimulus by means of some 

 nervous process of a physico-chemical nature. Given this 



