292 ORGANIC EVOLUTION CONSIDEEED 



nature does her work. The forces of nature do their 

 work in certain definite and uniform ways, so that we 

 can predict with certainty the results of a given set 

 of physical conditions. In every law of nature is 

 implied the idea that like causes produce like effects, 

 and that unlike causes produce unlike effects. As 

 the cause varies so must the effect vary. 



Law prevails from atom to world. All true science 

 is the embodiment of law. The natural sciences show 

 nature's methods of doing her work. Man's exist- 

 ence depends upon the fact that the laws of nature 

 are quite uniform. When he has learned them once 

 his knowledge holds good for an indefinite time. 

 They furnish a permanent basis for conduct and en- 

 able him to prophesy future results. Armed with the 

 knowledge of law, man is prepared to live in the 

 world and to make further progress. 



The succession of events in nature is uniform only 

 so far as the causes producing them are uniform. 

 The causes of certain classes of events are uniform, 

 and results in these cases may be repeated with math- 

 ematical exactness — as is the case with chemical 

 actions which produce compounds that are absolutely 

 alike. 



In other cases the causes vary, thus producing 

 unlike results, even where it might be supposed that 

 they would be alike. This is seen in the animal and 

 vegetable kingdoms, in which no two individuals of 

 even the same species are alike. Parent and offspring 

 always differ from each other. 



In the organic world there is no such thing as uni- 

 formity in nature in the sense that nature repeats 

 herself with absolute exactness. When we speak, 

 therefore, of the laws of nature, we do not mean 

 that the results of the operations of nature are neces- 

 sarily uniform. 



