PHYSIOLOGY Ixv 



and mechanism. But this physiological question has a far 

 deeper philosophical interest ; and when the problem is 

 regarded from that wider point of view, the opposite schools 

 are those loosely described as spiritualism and materialism. 



The method of science is now, and always has been, 

 exclusively materialistic : that is to say, the sole data of its 

 investigations are matter and energy ; every event, that 

 receives a scientific explanation, is analysed into some par- 

 ticular combination of matter and material energy. Now it 

 happened at the dawn of civihsation that men began to 

 speculate about the causes of things long before they had 

 any science or organised knowledge to guide them ; long, 

 therefore, before there was any possibiHty of their finding 

 those causes. In this position the mental craving was met 

 by the invention of a new kind of entity, different from 

 matter, and called spirit. All difficulties were immediately 

 levelled : What causes disease ? An evil demon. Why do 

 the winds blow ? A spirit is responsible. What is the 

 origin of the universe ? A god or gods made it ; and so on. 

 Thus all things received an easy explanation. I need not 

 recite the oft-told story of the dechne of spirits and the rise 

 of materiahsm in conjunction with the advance of civilisa- 

 tion. In no instance did the progress of knowledge reveal 

 the true existence of any entity apart from matter. One by 

 one the spirits were driven from the field of explanation : at 

 the present time they are all but banished from scientific 

 method, and survive only in extremely mitigated form in 

 the imaginations of the vulgar. 



Nowhere has the struggle been more strenuous than in 

 the region of physiology. Of all subjects which have excited 

 the curiosity of man, few are more enthralling, and few more 

 beset with difficulties, than the causes of the manifestations 

 of hfe and movement by which certain portions of matter, 

 named organisms, are differentiated from inorganic matter. 

 The difficulty was of course met in olden times by the hypo- 

 statisation of a new entity, often called the soul, but assuming 

 a vast variety of different shapes and conditions according 



