WHAT IT IS AND WHAT IT IS NOT. 65 



usually associated with the recognition of natural selec- 

 tion as the great motive power in organic change. 

 Darwinism was at first regarded as a "working hypoth- 

 esis." It is now an integral part of biological science, 

 because all opposing hypotheses have long since ceased 

 to work. It is as well attested as the theory of gravita- 

 tion, and its elements are open to less doubt. All in- 

 vestigations in biology must assume it, as without it 

 most such investigations would be impossible. Natural- 

 ists could no more go back to the old notion of special 

 creation for each species and its organs than astrono- 

 mers could go back to the old notion of guiding angels 

 as directors of planetary motion. Without the theory 

 of organic development through natural selection the 

 biological science of to-day would be impossible. 



In a third sense the word evolution is applied to a 

 method of investigation. It is the study of present con- 

 ditions in the light of the past. The 

 Evolution as a limi work of science ig the de _ 



method of study. . . y ,*,... 



scnptive part. This involves accuracy 



of observation and precision of statement, but makes 

 no great demands on the powers of logical analysis and 

 synthesis. The easy work of science is largely already 

 done. Those who would continue investigation must 

 study not only facts and structures, but the laws that 

 govern them. In the words of John Fiske, "Whether 

 planets or mountains or molluscs or subjunctive modes 

 or tribal confederacies be the things studied, the scholars 

 who have studied them most fruitfully were those who 

 have studied them as phases of development. Their 

 work has directed the current of thought." The most 

 difficult problems in life are susceptible of more or less 

 perfect solution if approached by the method of evolu- 

 tion. They can not be even stated as problems in any 

 other terms. In every science worthy of the name the 



