310 DOCTRINE OF EVOLUTION 



science. So much might be said, and yet it is not fitting 

 for the investigator to preach unduly. The lessons of 

 the doctrine must be brought home to each individual 

 through personal conviction. But because I firmly be- 

 lieve in the truth of the statement made in the opening 

 pages, namely, that science and its results are of prac- 

 tical human value, it is in a sense my duty as an advo- 

 cate of evolution to make this plain. 



The method of science is justified of its fruits. At the 

 very beginning we learned how, and how only, sure 

 knowledge can be obtained and how it differs from a be- 

 lief which may or may not correspond with the'truth. 

 Based upon facts of smaller or larger groups, scientific 

 laws are so many summaries of past experience, and they 

 describe in concise conceptual shorthand the manifold 

 happenings of nature. Their difference from belief in- 

 heres in their ability to serve as guides for everyday and 

 future experience. This entire volume is a plea for the 

 employment of common-sense as we look upon and in- 

 terpret the world in which we have our places and in 

 which we must play our roles. Our search for truth will 

 be rewarded in so far as we organize our common-sense 

 observations into clear conceptions of the laws of na- 

 ture's order. 



The doctrine of evolution enjoins us to learn the rules 

 of the great game of life which we must play, as science 

 reveals them to us. It is well to remember that a little 

 knowledge is a dangerous thing, but because evolution is 

 true always and everywhere, an understanding of its 

 workings in any department of thought and life clears 

 the vision of other realms of knowledge and action. 

 Perhaps the greatest lesson is at the same time the most 



