THE FORCES IN THE ORGANISM 59 



human eye, understand every detail of the laws of optics, know 

 how the rays which focus an image on the retina are converged, 

 refracted and reflected ; but how it comes about that we have 

 a sensation of the image, how we become conscious of it still 

 remains an impenetrable mystery. We may know the delicate 

 structure of the brain, follow each change, every chemical pro- 

 cess and motion of the atoms during the process of thinking ; 

 but how a thought arises, how we become conscious of an 

 object, remains a question to which there is no answer, nor 

 ever will be. As Du Bois Keymond said : " It will for ever 

 remain inexplicable why a certain number of atoms of carbon, 

 hydrogen, nitrogen, and oxygen should not be utterly indifferent 

 as to how they lie and move, how they did lie and move, and 

 how they will lie and move. It is impossible to see how their 

 correlated action produces consciousness. The mental processes 

 which are going on in the brain side by side with the material 

 processes offer no explanation acceptable to our reason. They 

 stand outside the law of causality, and are for that reason alone 

 as incomprehensible as a perpetuum mobile. As the world and 

 all individual thought originate in consciousness, so conscious- 

 ness is the final law to which we can reduce a phenomenon." 

 But though this greatest riddle may remain unsolved, the need, 

 deeply ingrained in our mind, of conceiving all processes and 

 changes as effects, and of searching for the causes of these 

 effects, finds, nevertheless, a high degree of satisfaction in the 

 endeavour to reduce each phenomenon to its cause. Even the 

 conviction that we shall never be able to fathom the truth will 

 not prevent us from striving after the truth for ever. 



