THE MECHANICAL SYSTEM AND ITS LIMITS 361 



that fill the universe. But has anyone ever seen this 

 vibrating ether ? It is the same with the theories that 

 explain the nature of electricity and magnetism. The 

 value of scientific theories is not that they can be 

 verified by direct observation, but that they bring all 

 the material under one point of view, and so make 

 it intelligible. Natural selection prevails wherever 

 there is life. 



Can science make the whole world intelligible to 

 us, then? 



When a man of science seeks to explain a 

 phenomenon he looks for the cause of it. When he 

 has discovered this cause his task is not over; the 

 question then arises, what was the cause of this cause ? 

 Even when this is settled the work is not ended. 

 Every cause is at the same time the effect of another 

 cause. We never reach an ultimate cause that is 

 cause only and not effect, because the chain of cause 

 and effect, the various links of which are the 

 phenomena of the universe, is infinite. 



We have, for instance, discovered the cause of the 

 erosion of the sea - coast in many places to be the 

 waves of the sea, the cause of these to be the lifting- 

 up of the surface of the water, and the cause of this 

 again to be the attraction of the sun and moon. 

 Science presses onward, and brings more and more 

 links of the chain of causes out of the depths of the 

 perplexing ocean of events. Will the whole chain 

 ever be brought to light ? No, that can never be. 



