GENERAL CONCLUSIONS. 285 



return, each of which teaches us a new law. And 

 since he is obliged to make a selection, it is to these 

 latter facts that the scientist must devote himself. 



No doubt this classification is relative, and arises 

 from the frailty of our mind. The facts that give but 

 a small return are the complex facts, upon which a 

 multiplicity of circumstances exercise an appreciable 

 influence — circumstances so numerous and so diverse 

 that we cannot distinguish them all. But I should 

 say, rather, that they are the facts that we consider 

 complex, because the entanglement of these circum- 

 stances exceeds the compass of our mind. No doubt 

 a vaster and a keener mind than ours would judge 

 otherwise. But that matters little ; it is not this 

 superior mind that we have to use, but our own. 



The facts that give a large return are those that we 

 consider simple, whether they are so in reality, because 

 they are only influenced by a small number of well- 

 defined circumstances, or whether they take on an 

 appearance of simplicity, because the multiplicity of 

 circumstances upon which they depend obey the laws 

 of chance, and so arrive at a mutual compensation. 

 This is most frequently the case, and is what' com- 

 pelled us to enquire somewhat closely into the 

 nature of chance. The facts to which the laws of 

 chance apply become accessible to the scientist, who 

 would lose heart in face of the extraordinary com- 

 plication of the problems to which these laws are not 

 applicable. 



We have seen how these considerations apply not 

 only to the physical but also to the mathematical 

 sciences. The method of demonstration is not the 

 same for the physicist as for the mathematician. But 



