308 THE FOUNDATIONS OF ZOOLOGY 



little reflection will show that the passage from physical phenomena 

 to psychical events is thinkable in exactly the same way, since all 

 plain practical folks think it every day and every moment of their 

 lives. As we use words, a mountain is physical, and to see a moun- 

 tain is a state of mind. Is not our confidence that if Professor 

 Tyndall were where the Alps could be seen, he might see them if 

 he had his eyesight, as reasonable and as implicit as our confi- 

 dence that a collision between two molecules will change their 

 motion ? If we can be said to pass by a process of reasoning 

 from the motion of two molecules before impact to their motion 

 afterwards, we can be said to pass, in the same way, from a physi- 

 cal burn to a psychical pain ; for we have no reason to doubt 

 and every reason to expect that a burn will hurt. Tyndall's asser- 

 tion that the passage from the physics of the brain to the facts 

 of consciousness is unthinkable, that they appear together, but that 

 nature does not tell us why, might be a contribution to human 

 wisdom if we were able to discover in nature any reason why 

 physical phenomena themselves appear together except the fact 

 that they do. 



" Modern science," says Huxley, with an insight more profound 

 than Tyndall's, "admits that there are two worlds to be considered, 

 the one physical and the other psychical, and that though there is 

 a most intimate relation and intercommunication between the two, 

 the bridge from one to the other has yet to be found ; that their 

 phenomena run, not in one series, but along parallel lines." 1 



The reduction of the phenomena of life to those mechanical 

 principles which hold good in the inorganic world would unques- 

 tionably show that these two worlds are in fact different aspects 

 of one and the same world. If such a discovery should ever be 

 made, we might well hope for untold practical benefits to man- 

 kind, like those which have followed every great advance in know- 

 ledge, but I cannot see how it could possibly show that man is 

 anything else than man, or mind anything but mind ; for when 

 we say we are able to pass from one physical event to another 

 physical event, all we mean is that one of these events is the sign 

 which leads us to look for the other with confidence. We most 



1 " Pseudo-Scientific Realism," p. 62. 



